Heat Pump Myths Busted: Real Insights from a UK Family Home

🏠 Introduction

Heat Pump Myths are everywhere.  I began writing this article after asking an AI bot what the most common questions were about air source heat pumps in the UK. The results were eye-opening — not because of the questions, but because of the amount of misinformation in the answers. Some of it is just ignorance, but some seems deliberately pedalled by folks with other agendas.

Hopefully, this article will set the record straight. I’ll answer these points with real-world experience, facts and figures, efficiency, Coefficient of Performance (COP) — backed up by years of data from my own system.

I’m not just writing this from theory. We’ve had our 5kW Vaillant Arotherm air source heat pump and 250 Litre Mixergy hot water cylinder running since October 2022 having replaced our gas boiler as part of the government Boiler Upgrade Scheme.

It has been  more efficient — and cheaper to run than our old gas boiler.  And has helped cut our home’s carbon emissions.

The heat pump keeps our 1930s semi-detached house in Sheffield warm, provides enough hot water for a family of four, and has given me first-hand insight into how heat pumps really perform.

As I write this article we are just about to enter our fourth winter with our heat pump. I think that experience puts me in a pretty good place to counter the myths, share some honest truths, and back it all up with years of data.

📖 Reading Guide

This is a long read (over 8,000 words) because it tackles 28 of the most common heat pump myths in detail, with real data and lived experience.

Use the Table of Contents below to jump straight to the questions that matter most — or scroll through at your own pace.

🔍 Common Heat Pump Myths in the UK

From costs to noise to winter performance, there are plenty of heat pump myths still circulating in the UK. Some come from outdated information, while others are based on misunderstanding how modern systems really work.

In the sections below, I’ll tackle the most common myths one by one—drawing on real data and lived experience from our own family home, as well as referencing external studies and materials where useful.

💷 How much does a heat pump installation cost in the UK?

Quick answer: A typical install costs £10k–15k before grants, but the BUS subsidy cuts this by up to £7.5k.

Myth: Heat pumps cost a fortune — tens of thousands of pounds more than a boiler.

Reality: A typical air source heat pump installation in the UK costs between £10,000 and £15,000, depending on house size, insulation levels, and whether radiators or pipework need upgrading. That’s more than a gas boiler upfront, but not wildly out of reach — especially when you apply the Boiler Upgrade Scheme grant for air source heat pumps. The scheme provides up to £7,500 off installations in England and Wales. Scotland also offers its own Home Energy Scotland funding and loans.

Context: In many cases, part of the total cost isn’t just the heat pump itself but putting right the install wrongs of the past — things like undersized pipework or poor heating system design choices in the home. A gas boiler can often be swapped like-for-like with little thought to the wider setup. A heat pump, by contrast, is never just a box installed outside — it’s part of the “heating system“. That means radiators, pipework, and controls all need to work together. Sometimes this requires upgrading all or some of the system, not just the heat source. The payoff is that you don’t just replace a boiler — you end up with a properly designed, future-proofed heating system that delivers comfort and efficiency for the long term.

Real world: When we installed our system, we claimed the BUS grant when it was £5,000. Today’s higher £7,500 grant makes heat pumps even more attractive financially. And once installed, the running costs are often lower than gas — especially if you system is efficient, you’re on a smart tariff or better still, both.

Another financial benefit often overlooked is that once you fully electrify your home, you can remove your gas meter and save on the daily standing charge. I wrote about our own experience doing this here: Goodbye Gas Meter.

Beyond the pounds and pence, a well-designed heat pump installation is future-proofing. With a typical lifespan of 15–20 years and minimal maintenance, it’s a one-off investment that upgrades your heating system as a whole, not just the heat source outside. That means your home is set up for decades of efficient, reliable comfort — at a time when gas is being phased out — delivering real long-term value.

💷 Cost reality: With the BUS grant, a typical heat pump install is £2,500–£7,500 more than a new boiler — but it’s a one-off investment that sets your home up for decades, with lower running costs and no gas bills.

💰 Are air source heat pumps worth it in the UK?

Quick answer: Well designed heat pumps can be cheaper to run than gas boilers — even on standard tariffs — and smart tariffs can boost savings further.

Myth: They’re too expensive to run.

Reality: Well designed and installed heat pumps can be cheaper to run than gas boilers — even without smart tariffs — because their efficiency (COP) often outweighs the spark gap between electricity and gas prices. With time-of-use tariffs and smart operation, savings can grow even further.

One of the barriers right now is the spark gap — the difference between gas and electricity prices. While heat pumps are much more efficient, the higher per-unit cost of electricity can limit savings if you don’t have the right tariff. That’s why the interplay between your system’s SCOP (seasonal coefficient of performance) and the unit rate of electricity is so important. I’ve broken this down fully in my article on SCOP versus pounds and pence.

Evidence from the wider UK market: Modelling by Nesta shows that even on standard tariffs, a well-designed heat pump can compete with gas because efficiency (COP/SCOP) offsets the higher unit price of electricity. With time-of-use tariffs, savings can increase further — Nesta’s analysis suggests households can save £200–£600 per year, and pairing with solar or battery storage can boost this even more.

Real world: I personally use Intelligent Octopus Go to drive down my running costs using the “holy trinity” of solar, batteries and a heat pump — with our EV as an extra bonus.  Our bills have reduced bills significantly compared to when we had gas.  I’ve detailed all the numbers in my Whole House Running Costs & Stats 2024 article.

You may not have that exact combination of technology, so I’ve compared different approaches with various other tariffs in my Best Heat Pump Tariff guide.

Monitoring: All performance figures and metrics (COP, SCOP, electric input and heat output) in this article are collected using Open Energy Monitor, an independent MID-approved billing grade heat meter and electricity meter setup. My heat pump also features on Heat Pump Monitor with hundreds of others.

⚠️ Important note: Many manufacturers’ internal monitoring is not accurate. Results should only be trusted if measured with independent billing-grade kit like Open Energy Monitor.

💡 Savings reality: Even on standard tariffs, heat pumps can be cheaper to run than gas thanks to their efficiency. With the right tariff, smart scheduling and automation, the savings only get bigger.

💡 How can you save even more with a heat pump?

Running costs don’t just depend on the heat pump itself — they depend on how smartly you use it.

• Shift hot water runs off-peak: As I explained in The Heat Pump Hot Water Golden Rules, moving hot water heating into cheap tariff windows can save a significant amount. Tools like Havenwise can automate this so you don’t have to think about it.

• Pick the right tariff: Not all tariffs are equal. Time-of-use options like Octopus Cosy and Octopus Agile can slash running costs if you align heating and hot water to off-peak slots. I’ve compared the options in my guide to the Best Heat Pump Tariff.

• Consider solar and batteries: Pairing  a heat pump with solar PV (and optionally a battery) can further reduce imports from the grid. In my own setup, seven months of the year my solar generation exceeded the heat pump’s usage. That means free, renewable heat for most of the year. For independent insights on solar and battery setups, I recommend the Gary Does Solar YouTube channel.

• Real World Solar Data: You might also found my own monthly solar generation figures going back to 2018 useful.
• Real World Heat Pump Data: You might also found my own monthly heat pump usage and performance figures going back to 2018 useful.
• Supplier Options: If you do decide to change your supplier to Octopus Energy, you can claim £50 free credit when switching using my referral link. Thank you if you decide to do that.

💡 Savings reality: With the right tariff, smart scheduling, and automation, air source heat pumps can be cheaper to run than gas boilers — and even cheaper still if you combine them with solar and batteries.

🥶 Do air source heat pumps work in UK winters?

Quick answer: Yes — even below freezing, modern heat pumps keep homes warm with real-world efficiency close to 3x.

Myth: Heat pumps don’t work when it’s cold.

Reality: Even during freezing conditions, my Vaillant Arotherm air source heat pump achieved a Coefficient of Performance (COP) of 2.87 for space heating (287% efficiency), and 2.49 for hot water. Combined, that’s a COP of 2.84 – nearly three times as much heat out as electricity in. Modern cold-climate models are engineered to keep working efficiently even at design temperatures of –15 °C or below — far colder than anything most UK homes will ever face.

Real world: On the coldest day of January 2025 it was sub-zero outside all day, yet the house stayed at a steady 20 °C indoors. You can see the full stats and charts in my detailed third winter performance analysis.

❄️  Winter reality: Heat pumps absolutely work in UK winters — with real-world efficiency close to 3×, even below freezing.

Here is the Open Energy Monitor graph from that cold day in January 2025 and a direct link to the graph.

🗑️ But a COP of 2.87 is rubbish, isn’t it?

Myth: A heat pump with a COP under 3 isn’t efficient enough.

Reality: COP — Coefficient of Performance — is a snapshot of efficiency at a point in time (an hour, a day, or even a week). On the coldest day, my Vaillant Arotherm air source heat pump recorded a COP of 2.87 — which still equates to nearly three times the heat output for each unit of electricity. That’s not rubbish — it’s simply the low end of performance in freezing conditions.

But performance rises quickly as the temperature does: around 4.5 (450%) at 6 °C, and over 5.5 (550%) at 13 °C, as shown in the chart below taken from Second winter with our Vaillant ASHP.

This chart is based on real-world performance data collected between November 2023 and April 2024. It shows the average daily COP for space heating, plotted against the average daily outdoor temperature recorded during that period. The pattern is clear: efficiency improves steadily as the weather warms.

Figure: Average daily COP for space heating vs. outdoor temperature, based on real-world data from November 2023 to April 2024.

The bigger picture comes from SCOP — Seasonal Coefficient of Performance. SCOP averages performance across the whole year, through all weathers, and is the more useful metric for running costs and carbon. According to my 2024 results published in Whole-house running costs and stats 2024:

• Heating only: 4.45

• Hot water only: 3.84

• Combined (heating + hot water): 4.23

Real world: While my lowest daily COP was 2.87 on a freezing January day, across the full year my system delivered more than 4× the heat for every unit of electricity. That’s why heat pumps work in practice — efficiency dips in rare cold snaps, but the year-round performance is outstanding.

❄️ Do heat pumps work in Scotland’s winter?

The myth: It’s common to hear that Scotland is “too cold” for heat pumps to work efficiently.

The reality: The data shows otherwise. While Scotland is cooler than southern England, truly freezing days are surprisingly rare.

Average heating season temperatures in Scotland vs England

Across the heating season (Nov–Apr), average daily mean temperatures are:

How many days really stay below freezing?

Days where the daily mean temperature (24-hour average) is at or below 0 °C are rare, even in Scotland:

*Motherwell values use the nearby Glasgow/Bishopton station as the inland Central Belt proxy.

Frost days vs freezing days – what’s the difference?

• Frost day = minimum temperature dips below 0 °C overnight.

• Freezing day = the whole day’s average stays ≤ 0 °C.
  👉 Frost is common, but true freezing days are much less frequent.

Why heat pumps still perform well in UK winters

• Even in central Scotland, the heating season sees only ~8 freezing days.

• Sheffield averages ~4, and Oxford just ~1.

• Most of the winter, daily mean temperatures are well above zero, keeping heat pumps in their high-efficiency operating range.

A good installer will take into account the locate climate and design the system to cope with even the coldest days whilst still performing efficiently at other times.

Note: Because of the cooler outside temperatures in Scotland, the very same house placed in Oxford would performance better than if we placed it in Motherwell.  Remember this when comparing performance between systems.  Location matters.

Sources

• Met Office – Sheffield (Weston Park)

• Met Office – Oxford (Radcliffe Observatory)

• Met Office – Glasgow/Bishopton (proxy for Motherwell)

🛋️ Will my house feel warm with a heat pump?

Myth: Heat pumps only provide lukewarm heat — the house will never feel properly warm.

Reality: Heat pumps work differently from how most gas boilers are installed. Instead of blasting very high-temperature water (70–80 °C) in short bursts, like many gas boiler systems, heat pumps use weather compensation — adjusting radiator flow temperature according to the outside weather, so that heat input continuously matches the home’s heat loss. This “low and slow” approach keeps the house at a steady, comfortable temperature rather than swinging between hot and cold. With properly sized radiators, the rooms stay warm and comfortable even on freezing days.

Ironically, as Nathan Gambling, host of the BetaTalk podcast, regularly reminds us, condensing gas boilers (developed in the late 1970s/early 1980s) should always have been controlled via weather compensation. But for whatever reason, the majority of the UK industry and installers went down a different path — relying on basic on/off controls and now layering in third-party thermostats like Hive and Nest, which disrupt how these systems are meant to modulate.

Real world: In our 1930s semi, the difference has been striking. With the boiler, the rooms were always HOT then cold, as the thermostat clicked on and off. With the heat pump, it’s consistently toasty — so much so that you can’t tell how cold it is outside without looking at your phone.

Like many so-called heat pump myths, the idea that your home will never feel properly warm just doesn’t hold up once you look at how the systems are designed to run.

📸 This is a photo of my 5 kW Arotherm heat pump in the snow.

🌡️ Will my radiators get hot with a heat pump??

Quick answer: Yes — radiators still get hot with a heat pump, but only as hot as needed to keep your home comfortable.

Myth: Radiators won’t feel hot with a heat pump.

Reality: Radiators with a heat pump do get hot — but only to the temperature required for the conditions. On cold days they’ll be hotter, on mild days just warm. This is how the system stays efficient while still keeping the house at a steady temperature.

Real world: In our retrofit, radiators were upgraded where needed, and the house stays evenly warm through winter — no lukewarm problem at all. In fact, the comfort is better: instead of hot-and-cold blasts, the house feels consistently cosy all day long (the only thing we miss is radiators hot enough for drying socks!).

🛋️ Comfort reality: Heat pumps aren’t about blasting heat and then switching off. They’re about putting just the right amount of heat into the radiators — hotter or cooler — to keep the indoor temperature steady and comfortable all the time.

🔥 Do heat pumps need to stay on all the time?

Myth: Heat pumps should run like boilers — on/off in short bursts.

Reality: Heat pumps are designed to work differently from gas boilers. Instead of blasting heat at full power and then switching off, they use weather compensation and modulation: adjusting the flow temperature of the water in your radiators or underfloor heating depending on the outside temperature.

The aim is simple — to match the heat your house is losing with just the right amount of heat going in. On a mild day, the water temperature in your radiators might be 30–35 °C. On a freezing day, it could rise to 45–50 °C. The system slides up and down automatically, keeping efficiency high.

Because of this “low and slow” approach, a heat pump runs steadily in the background instead of cycling hot and cold. That’s also why your radiators don’t feel scorching hot like they might with a gas boiler — they only need to be as hot as the weather demands.

Real world: In our 1930s semi, the house feels consistently comfortable. The only “problem” is you forget what the weather is doing outside — you have to check the weather app on your phone before leaving the house to know whether you need a coat.

🔥 Comfort boost: Unlike boilers that cycle hot/cold, heat pumps provide steady, even warmth. Many people say it’s the biggest (and most unexpected) benefit.

🕹️ Are heat pumps complicated to use?

Myth: Heat pumps are confusing and difficult to operate.

Reality: Once a system is properly designed, commissioned, and handed over, it should be simple. Heat pumps with weather compensation just run in the background, automatically adjusting flow temperature to match your home’s heat loss. The installer’s job is to set the heat curve correctly during commissioning — once that’s done, you shouldn’t need to fiddle with on/off controls.

⚠️ Important: Always use the manufacturer’s own controls for weather compensation. Don’t add third-party on/off thermostats like Hive or Nest — they disrupt how a heat pump should modulate and will hurt both comfort and efficiency. As Custom Renewables explain, this stop-start control method “can lower the heat pump’s efficiency and raise your energy bills.”

Real world: In our house, I never touch the controls. Nobody runs to the thermostat because they’re cold — the house just stays consistently comfortable. The handover from my installer was key: they walked me through the controls, explained the logic behind the system, and made sure I understood what not to touch. Every homeowner should expect the same from their installer.

If you do struggle with fine-tuning the heat curve, there are even third-party optimisers like Havenwise that can manage flow temperatures remotely and make the smart decisions for you.

🕹️ Usability reality: With proper commissioning and a clear handover, heat pumps are “set and forget” — far less hassle than a boiler’s on/off thermostat

🔊 Are air source heat pumps noisy?

Quick answer: No — modern units are very quiet, often comparable to everyday background sounds like a fridge, dishwasher, or modern combi boiler.

Myth: Heat pumps are loud and disruptive — like having an air conditioning unit running outside all winter.

Reality: Modern air source heat pumps are surprisingly quiet. Most produce a gentle hum, typically in the 40–60 dB range — similar to a fridge or a modern combi boiler — and all new systems must meet the UK’s strict planning noise limit of 42 dB at the nearest neighbour’s window.

External validation: A Nesta study on neighbourhood noise levels with heat pumps found that even on streets full of installations, the overall soundscape barely changed. In other words, installing multiple heat pumps “makes almost no difference” to the background noise.

Real world: Our Vaillant unit just purrs away like a cat, and it’s sat right by the back door of the dining room. We never hear it indoors. In the garden, the flue from my neighbour’s gas boiler is louder.

🔇 Noise reality: If installed correctly and in a sensible location, a modern heat pump is no louder than typical background sounds — and often fades into the ambient noise of daily life.

🏚️ Do heat pumps work in old houses?

Quick answer: Yes — heat pumps work in old houses as long as the system is properly designed, and studies show owners of older homes are just as satisfied as those in new builds.

Myth: Heat pumps only work in new builds or ultra-insulated homes. Old houses are unsuitable.

Reality: Heat pumps can work in homes of all ages — including older, less efficient ones. The key is a proper heat loss calculation and good system design. UK government research has shown successful retrofits in properties like 1930s semis, while a Nesta survey found that 81% of heat pump owners in older homes report equal or higher satisfaction compared to those in newer builds. Adding insulation or draught-proofing will always improve efficiency, but it isn’t a barrier to fitting a heat pump

Real world: Our own 1930s semi in Sheffield is proof. With the right design and a few radiator upgrades, the heat pump has kept us warm through multiple winters, supplying both heating and hot water reliably — no special insulation project required.

🏠 Old home reality: With the right design and installer, age isn’t a barrier — heat pumps can run efficiently in anything from 1930s semis to Victorian terraces and beyond.

🧱 Do I need to insulate my home before getting a heat pump?

Myth: You can’t install a heat pump unless you fully insulate your house first — the classic “fabric first” argument.

Reality: Insulation always helps, no matter what your heating source is — gas, oil, or electric. But it’s a myth that only brand-new, ultra-insulated homes can run a heat pump. In fact, research published in Buildings & Cities (Eyre et al., 2023) challenges the traditional “fabric-first” retrofit philosophy, arguing that, given the urgency of heat decarbonisation, many existing homes can successfully transition to a heat pump without major insulation upgrades — though fabric improvements remain beneficial where low-cost options are available.

Nigel Banks offers a complementary perspective in his LinkedIn article Fabric Fifth…, placing major fabric upgrades as the fifth priority and emphasizing that immediate steps such as installing air-source heat pumps, deploying smart controls, and enabling flexible energy use may accelerate decarbonisation more effectively.

Practical reality: Any heating system — gas or heat pump — benefits from good insulation. The more you can add, the lower your heat loss, and the lower your heating bills. While Fabric Fifth shows you don’t need an ultra-insulated home to run a heat pump, there are cases where fabric improvements first can make sense. Better insulation — loft, cavity or solid wall, double glazing — reduces the amount of heat your home needs. That in turn means smaller radiators may be sufficient, expensive pipework upgrades could be avoided (Heat Geek explains why), and the whole system runs more efficiently.

In short: most homes can take a heat pump without major insulation work, but fabric upgrades can sometimes save money and future-proof your heating system.

Real world: Our 1930s semi isn’t “passivhaus standard”, far from it — it’s just reasonably insulated. The heat pump still works brilliantly.

💡 Tip: Upgrading insulation before or during install may avoid extra work on radiators or pipework. But it doesn’t all have to be done in one big bang — you can make improvements like loft insulation, glazing, or cavity fill later, when it suits. Any upgrade to the fabric or radiators is likely to improve system efficiency and may reduce running costs.

🏠 Do heat pumps only work with underfloor heating?

Quick answer: No — heat pumps work perfectly well with radiators, as long as the system is properly designed.

Myth: Heat pumps can’t work with radiators — you have to install underfloor heating.

Reality: Heat pumps don’t need underfloor heating to perform well. With correctly sized radiators, they can deliver the required heat at lower flow temperatures. In some homes, radiators may need upgrading to larger ones, but underfloor heating is helpful, not essential. In fact, a study published in the journal: Building Services Engineering Research and Technology found that almost a third of UK homes could run low-temperature heat pumps effectively without any radiator upgrades at all.

Real world: Our 1930s semi is a full radiator retrofit with no underfloor heating at all. A few radiator upgrades were needed, and the system keeps the whole house warm and comfortable through winter.

🛠️ Underfloor reality: Underfloor heating can be a great match for heat pumps, but radiators work just as well when the system is designed properly.

📸 Below is the largest radiator in our retrofit — a K3 triple-panel model. It allowed us to keep flow temperatures low while still meeting the heat loss of that room.

👉 Note: The rest of the rooms in our house use standard K2 radiators. You don’t need a house full of larger K3s to get an efficient system — just the right size radiators in the right places.

🪜 Can heat pumps work with microbore pipes?

Myth: Heat pumps can’t work with microbore pipes — you’ll need to rip everything out.

Reality: Microbore pipework (anything under 15 mm, such as common 8mm or 10 mm microbore pipes) does create challenges because it restricts flow rates — a bit like trying to blow water down a thin straw. But that doesn’t mean a heat pump is impossible. As Heat Geek explain in their detailed guide on microbore pipework and heat pumps, good system design and clever hydraulic strategies often make it perfectly workable.

System design matters most — a heat pump can be tailored to compensate for microbore. Room-by-room (and whole house) heat loss calculations will show whether the pipework can cope as is, or what tweaks are needed. In some cases, design may show that only a small part of the system needs a re-pipe — not the whole house. Often end rooms are fine, with just the main loops needing attention.

And the good news is that because microbore is usually found in newer built houses, then the insulation should be better so the heat loss is lower, potentially leaving you with less need for giant pipework.

Good installers (who understand core system design principles) can design around microbore without always resorting to a full re-pipe — or any replacement at all. The maths may suggest all is well without changes, or perhaps you need to go down the hydraulic separation route.

The downsides of keeping microbore:
a. Potentially more kit needed (e.g. extra pumps/buffers), which means more cost and more space.
b. Some efficiency hit if more kit required vs. full-bore pipework / open-loop setup.

🚨 Industry rant: House builders are still fitting microbore with new gas boilers in 2025 — guaranteeing homes could need retrofitting almost immediately if they want a heat pump. The heating design could have been done right from day one, with just a little thought and knowledge.

Real World: By having your heat pump installed into a newly designed system, your house is set for decades to come. You’re not just fixing today’s heating — you’re futureproofing the property properly, in a way gas boiler swaps almost never achieved.

💧 Do I need to worry about water quality in a heat pump?

Myth: A magnetic filter and some inhibitor are enough to protect your system — no need to think about water quality.

Reality: Even with advanced pumps or underfloor loops, poor water quality can lead to corrosion, scaling and sludge — all of which reduce efficiency, raise running costs, and shorten system life. That’s where VDI 2035 comes in: a standard designed to protect systems without relying on guesswork or heavy chemical dosing. As highlighted in Installer Online’s guide to VDI 2035 for heating systems, it sets clear parameters for conductivity, hardness, and pH to prevent scaling and corrosion in a more reliable way than traditional inhibitor-only approaches.

VDI 2035 focuses on controlling:

• Conductivity & hardness (demineralised water prevents scaling)

• pH levels (kept neutral-to-alkaline to avoid corrosion)

• Oxygen ingress (tight, sealed systems prevent rust)

VDI 2035 is becoming a recognised best-practice framework in the UK, giving installers and homeowners a clear way to safeguard efficiency and longevity.

Real world: Too many installs just fit a magnetic filter and throw in inhibitor — without testing fill water, conductivity, or pH. And they often don’t come back to check it annually, which VDI 2035 explicitly recommends. That’s risky. A proper through flush at install removes debris and sets the baseline for clean, low-conductivity water, and regular testing keeps it that way. Companies like Thoroughflush are experts in VDI 2035 — providing the flushing equipment, test kits, and support to get it right.

💡 Tip: Water quality isn’t a one-off job. VDI 2035 encourages annual checks on conductivity, pH, and oxygen levels — so your system stays efficient and protected for the long term.

🧰 Does external heat pump pipe insulation really matter?

Quick answer: Yes — poor-quality insulation on outdoor pipework can quickly degrade, wasting heat and cutting system efficiency.

Myth: Any old pipework lagging will work.

Reality: I’ve seen far too many installs on social media where external pipework is wrapped in basic lagging, often held together with cable ties. Within a year or two it starts to split, slip, or soak up water — all of which waste heat before it even gets into the house. Research shows that wet or degraded insulation can lose 1.3 to 1.9 times more heat than when dry, according to an experimental study on heat loss in pipelines. (SN Applied Sciences study on wet insulation heat loss)

That’s why most good engineers now specify professional-grade systems like Primary Pro, which are UV- and weatherproof with sealable joints, or they combine insulation with high-quality external trunking such as Inaba Denko. Both approaches keep the insulation protected and effective for years — and are well worth requesting if your installer suggests cheaper alternatives.

Real world: My installer used Primary Pro insulation on the external run when the heat pump was fitted. Three winters later, it’s still solid, weatherproof, and exactly where it should be — no slipping, no splitting, just doing its job quietly in the background.

💡 Tips:

• Make sure the insulation continues through the wall into the property — a bigger core should be drilled so the pipework stays insulated all the way, not left bare through brickwork.

• Don’t accept basic lagging and cable ties on external runs — ask for proper weatherproof insulation and protection.

📸 Photo: My Primary Pro insulation, still performing flawlessly three years after installation.

📐 Why does design and installation quality matter?

Myth: Heat pumps are all the same — if it’s installed, it will work.

Reality: With gas boilers, a poor install might mean a small hit on efficiency — perhaps 70% instead of 85%. With heat pumps, the gap is far bigger: efficiency can vary from 250% to 500%. That difference can make or break running costs.

There’s no “rule of thumb” shortcut here. Every system needs a room-by-room heat loss calculation, proper pipe sizing, and flow temperatures matched to the building.

Working with an installer who really understands low-temperature heating design principles is the single biggest factor in whether your heat pump will perform well.

Tools like Spruce now allow installers to create detailed survey reports and design documents.

Real world: My system works well because it was designed and installed by award winning installer Damon Blakemore, an engineer who understood the core principles of low-temperature heating design.

I reviewed the book Heat Pumps Unlocked because it explains these principles so well — and it mirrored the lessons I’d already seen first-hand with my own system. It’s a clear, practical guide that demystifies design in a way most technical manuals don’t.

And at Installer Show 2025 I picked up a copy of The Pocket Guide to Low Temperature Central Heating by Ian Edgeworth which is another great resource.

📐 Design reality: Emma Bohan, Managing Director at IMS Heat Pumps, puts it simply: “Well designed, well installed heat pumps just work.” (IMS Heat Pumps)

📊 What is the index circuit?

Reality: The index circuit is the loop in your heating system with the highest resistance. It’s not always the longest or furthest away, but the one that’s hardest for water to circulate around.

As Rob Dyer, Technical Sales Support Engineer at Grant Heat Pumps, explains in Installer Online, correct pipework sizing and accounting for the index circuit is fundamental to achieving proper flow, quiet operation, and long-term efficiency.

Why it matters: If the index circuit is ignored, the whole system underperforms. Radiators may never get enough flow, they never get properly hot, efficiency drops, and comfort suffers. This is why careful system design and proper heat loss calculations are so important in a heat pump setup.

Real world: This is why microbore pipework is such a tough ask — the resistance is so high. Which neatly brings us back to the question: can heat pumps work with microbore pipes? The answer is yes, but only with careful design and, often, compensating measures.

🏗️ Do air source heat pumps require planning permission?

Myth: Installing a heat pump is a hassle because you’ll always need planning permission.

Fact: In most of England, air source heat pumps fall under permitted development rights—meaning you don’t usually need formal planning consent, provided siting and noise conditions are met. The UK Government Planning Portal confirms the rules for air source heat pumps.

Since 29 May 2025, installations in England are even simpler: the 1-metre boundary rule has been scrapped, larger units up to 1.5 m³ are now allowed, and detached homes can install up to two pumps—making installations far more flexible and accessible, especially for homes with limited outdoor space.

This is outlined in a helpful Vito Energy article on the new UK heat pump rules to simplify installation for millions of homes. For installers, the MCS guidance on permitted development and the MCS-020 standard sets out the technical detail they need to be aware of.

But remember—Scotland and Wales have different rules.
In Wales, heat pump installations may still require planning permission if placed within 3 metres of a property boundary or on listed/conservation-area properties. Check the Welsh Government’s guidance on heat pump planning rules for details.

In Scotland, installations typically fall under permitted development rights, but certain properties—like listed buildings and those in conservation areas—may still need permission. The Snugg blog summarises Scotland’s relaxed planning rules for heat pumps.

Real world: In our case, the unit sits neatly against the dining room wall and passed the dB limit checks at neighbours’ windows—fully compliant under England’s permitted development rules—so no planning permission was required.

💡 Tip: Always check with your installer, as they should know the planning requirements for your specific location and requirements could have changed since this article was first published.

⚡ Do heat pumps stop working in a power cut?

Myth: Gas boilers will keep running in a power cut, but heat pumps won’t because they rely on electricity.

Reality: Both heat pumps and modern gas boilers stop in a power cut in the UK — because boilers also need electricity for their pumps and control boards.

Real World: As my solar and home battery setup is quite old, it doesn’t currently have UPS (uninterruptible power supply) or power-cut protection that is capable of running the whole house, so in a blackout my system would also go off. But with the right solar and battery backup, it is possible to keep essential loads — and in some cases a heat pump — running. If I were purchasing my solar and battery again right now, I would certainly look at that option. And if you live in an area prone to power cuts, it’s worth considering too.

⚡ Remember: Gas boilers need electricity as well — so they also stop in a blackout. With a modern solar + battery setup, you may be able to keep heating and other essentials live when the grid goes down.

🌍 Are heat pumps really green if the grid still uses gas?

Myth: Heat pumps can’t really be called green if most of our electricity still comes from gas.

Reality: A modern heat pump typically delivers 3–4 units of heat for every 1 unit of electricity used — known as its Coefficient of Performance (COP). That means even if the electricity is partly generated from gas, the carbon emissions per unit of heat are far lower.

According to National Grid ESO’s carbon intensity data, the UK grid is rapidly decarbonising, and every year heat pumps become cleaner to run. That means a heat pump installed today will only get greener over its lifetime as more wind and solar come online.

Real world: In 2024, my own Vaillant heat pump achieved a seasonal COP of 4.23 (423% efficiency). That means for every unit of electricity, the system produced more than four units of heat. Even if that electricity had come entirely from gas, the overall emissions would still be lower than burning gas directly in a boiler. And of course, the reality is much better than that — a big chunk of my electricity comes from my own solar installation alongside the rapidly greening UK grid.

I’ve share all our monthly performance numbers in my Heat Pump Performance History article.

🌍 Green reality: A heat pump isn’t just “as green as the grid” — it multiplies the benefit of every clean kWh, and future-proofs your home as the UK moves towards its net zero targets

🔧 What is the lifespan of a heat pump?

Myth: Heat pumps are new, experimental technology and prone to failure.

Reality: Heat pumps aren’t new at all. The first ground source heat pump was built in 1927 by Graeme Haldane, and the same vapour-compression technology is used in fridges, freezers, and air conditioners worldwide.

In fact, almost every supermarket uses air-to-air heat pumps for heating and cooling. Air-to-water heat pumps (like mine) are just another application of the same proven, well-established technology.

History fact: Though natural gas feels like the UK’s “traditional” heating fuel, it’s actually a relatively recent arrival. The first successful trial of importing liquefied natural gas took place at Canvey Island between 1959 and 1960. After that, Britain didn’t begin the nationwide conversion from town gas to natural gas until the national conversion programme of 1967–1977. That means the gas system we think of as “conventional” actually came into UK homes more than 30 years after the first ground source heat pump was built in 1927.

As my friend Nathan Gambling often reminds listeners on his Betatalk Podcast, heat pumps are not some new, untested technology — they’ve been around for nearly 100 years. They’re already widely used in colder European countries like Scandinavia, which is about as strong a reliability test as you can get.

Most heat pumps have a lifespan of 15–20 years, similar to a gas boiler, and require very little servicing beyond routine maintenance.

Real world: As I write this, we’re just about to enter our fourth winter with our Vaillant heat pump in a 1930s semi. It’s been consistently reliable, with no breakdowns to date — just quiet, steady service.

🛠️ Reliability reality: Heat pumps are a low-maintenance, proven technology, widely used worldwide, with lifespans comparable to boilers.

🛠️ Do you need to rip out everything for a heat pump?

Reality: It depends.

• High performance retrofit: More upfront work and cost, but allows your heat pump to run at really low flow temperatures for maximum efficiency.

• Simpler installation: Less upfront disruption, still works fine, but you might take a small hit on efficiency.

It also depends on your starting point. If the house has microbore pipework or other restrictions, then upgrades may be unavoidable. Even standard 15mm copper pipework can sometimes be undersized — in my case, the ground floor needed the main pipework run replacing because calculations showed that the existing 15mm copper couldn’t carry the heat demand required. On the other hand, you might get lucky and find the existing system is already adequate for the heat loss of the house.

Either way, a good installer will walk you through the trade-offs so you can make the right choice for your home.

Real world: My own retrofit installation was disruptive because I decided to do everything in one go — radiator upgrades, pipework replacement, the lot — to futureproof the system. But there’s nothing stopping you swapping radiators later down the line, for example when you decorate a room. This can also help improve overall system COP (Coefficient of Performance) and efficiency.  But you do need to address any issues with the fundamental pipework like I did.

🚿 Can a heat pump provide enough hot water for a family home?

Quick answer: Yes — modern systems deliver 50–60 °C hot water, more than enough for daily use.

Myth: Heat pumps only provide lukewarm water.

Reality: Modern air source heat pump systems heat water to around 50–60 °C, which is more than enough for showers, baths, and daily use. In fact, in 2024 my system delivered a COP of 3.84 across 700 hot water runs — meaning nearly four times as much heat out as electricity in. That’s far more efficient than a gas boiler (typically 80–95% at best) or an electric immersion (100% at most).

The graph below shows the COP and outside temperature for all 700 hot water runs in that study.

Remember: storing hot water in a cylinder is no different whether you’re heating it with a gas boiler or a heat pump. The only real difference is that gas can push water hotter if you want it to — but in day-to-day use, 50–60 °C from a heat pump is plenty.

💧 Comfort reality: Showers, baths, and taps feel exactly the same. The only difference is what’s heating the cylinder in the background.

I personally think the MCS (Microgeneration Certification Scheme) guideline of 45 litres per person per day is far too low. If you’re an active family juggling school runs, work, gym, football, dance classes, and everything else, you’ll need more. A well-sized hot water cylinder makes all the difference.

💧 Tip: Don’t just accept the “45 L per person” rule of thumb. Talk to your installer about your family’s real lifestyle — gym, school runs, showers, sports. Cylinder sizing is personal, as is the approach to reheating it.

That’s why I went into detail in my article on cylinder sizing and mixing. With the right cylinder, and by mixing hot with cold at the tap, you can get far more usable hot water than the raw cylinder volume suggests.

Most systems also include an automatic legionella protection cycle, and have an immersion heater backup if needed — so there’s no risk of running out of safe hot water.

Real world: In our 1930s semi, the 250L Mixergy cylinder easily provides enough hot water for a family of four. We’ve never run out.

And here’s a financial benefit many overlook: with a larger cylinder, you can schedule heat pump hot water runs for off-peak electricity tariffs. By heating at the cheapest times of day, you save money without compromising comfort — something you simply can’t do with gas. I’ve written up the detail in my guide to the golden rules of heat pump hot water.

💷 Money saver: Pair a larger hot water cylinder with an off-peak tariff, and you can heat water cheaply at night or when electricity is cheapest. Comfort stays the same, but bills shrink.

🦠 Is Legionella a risk with heat pumps?

Myth: Heat pumps are dangerous because lukewarm hot water around 50 °C breeds Legionella bacteria.

Reality: While Legionella bacteria can grow between 20–45 °C, there’s no evidence of legionnaires’ disease deaths from residential properties. Studies show single- or multi-family homes don’t have outbreaks — most risks come from complex commercial systems (NCBI research). For domestic hot water, the engineering consensus is that storing around 45–50 °C is efficient and safe, with a once-weekly anti-Legionella cycle up to 60 °C as an extra precaution. Heat Geek’s guide to hot water temperatures, scalding and Legionella explains why maintaining 60 °C all the time is unnecessary with modern heat pumps.

Real world: In practice, keeping hot water stored at 60 °C all the time just isn’t efficient with a heat pump. Our heat pump hot water golden rules show that around 45–50 °C gives the best balance of comfort and efficiency, while a timed boost to 60 °C once a week covers the safety aspect.

🛁 Comfort/safety reality: Day to day, hot water at 45–50 °C feels the same — safe for showers and baths. The only difference is how efficiently your system manages the storage temperature in the background.

💡 Tech tip: Modern heat pumps can generate hot water above 60 °C themselves, meaning the Legionella protection cycle can be run by the heat pump — rather than relying on the less efficient electric immersion heater.

🔮 Will heat pumps become obsolete if hydrogen takes over?

Myth: Heat pumps are just a stopgap; hydrogen boilers will soon replace them.

Reality: Heat pumps are the core technology supported by the UK’s net-zero heating strategy. By contrast, hydrogen boilers remain highly uncertain — they’re less efficient (a heat pump delivers 3–4 times more heat per unit of electricity), more expensive, and face major infrastructure challenges around producing, transporting, and storing hydrogen safely. Several UK hydrogen heating trials have already been scaled back or cancelled, signalling a clear policy shift toward electricity-based solutions like heat pumps.

As Greg Jackson of Octopus Energy has argued: “Hydrogen is fantastic for steel, shipping and aviation — but it’s a distraction for home heating. Electrification is the clear path.” (source)

Real world: One of my key motivations was to get all the pipework and radiator upgrades sorted upfront, as a one-off project that ensures efficiency now and into the future.

🔮 Futureproof reality: Hydrogen heating is still experimental. Heat pumps are here to stay — and with good design, their value endures.

🏡 Will a heat pump add value to my home?

Myth: A heat pump won’t add any value to my property if hydrogen boilers take over.

Fact: Heat pumps are not experimental or short-lived — the core technology has been around for nearly 100 years and is the main heating solution backed by the UK’s net-zero strategy. Hydrogen is not a realistic competitor: unlike electricity, you can’t buy off-peak hydrogen or generate it yourself with solar PV, which makes heat pumps both smarter and cheaper to run. And according to Knight Frank research on EPC improvements and property values, boosting a home’s energy performance (EPC) can increase its value by up to 20%, showing that efficient, future-proof heating is viewed as a property asset.

Real world (my home): Our system was designed with proper pipework, radiator sizing, and flow temperatures to match the heat loss of the house. That means it’s future-proofed — whether the heat source changes in 15–20 years or not, the distribution system is already right. From a property perspective, a well-installed low-carbon heating system can also be a selling point, adding to the resale value of the home.

✅ Conclusion

This article set out to bust the most common heat pump myths in the UK with real-world evidence. From “they don’t work in winter” to “they’re too expensive,” these worries don’t hold up once you look at the data.

In our own 1930s Sheffield semi, a properly designed 5kW Vaillant Arotherm has kept a family of four warm and in hot water for years — with every minute logged by independent, billing-grade monitoring. That lived experience, combined with hard data, shows that heat pumps simply work.

Industry leaders echo the same truth. Greg Jackson, CEO of Octopus Energy, says: “Heat pumps aren’t some futuristic dream — they’re already cutting bills for households across the UK today.” And as Emma Bohan of IMS Heat Pumps puts it: “Well designed, well installed heat pumps just work.”

Futureproofing is the key theme. Whether it’s upgrading radiators and pipework once, or tackling insulation improvements step by step, the right design ensures your system works efficiently for decades — whatever the energy landscape looks like. Hydrogen may be a distraction, but a well-installed heat pump is already a low-carbon, cost-saving solution today.

👉 Want to see real-world performance data? Explore live dashboards and case studies here on Energy Stats UK, or dive into my Open Energy Monitor feed — logging every minute of my system’s performance over years.

I also publish monthly usage and efficiency data from our heat pump gong back to October 2022 that you may find useful.

If you own a Vaillant system yourself, I’ve also put together a Vaillant Arotherm heat pump guide — a collection of three years’ worth of findings, documents and data.

Data note: All figures (COP/SCOP/electric input and heat output) in this article come from Open Energy Monitor, an independent MID-approved, billing-grade metering setup. My system is also tracked on Heat Pump Monitor alongside hundreds of other heat pumps. Manufacturer dashboards are not always accurate — only billing-grade equipment like this can be fully trusted.

✅ Bottom line: Heat pumps aren’t about myths — As my installer Damon Blakemore says, it’s about nailing the 4 basics; Survey, Design, Installation and Commissioning. Get all those right, and they just work.

🔧 What to look for in a heat pump installer

Not all installers are equal. Don’t just look for shiny badges on their website. Many accreditations are simply tick box exercises and do not always equate to competency. The real test is whether they can explain — and apply — the core principles that make heat pumps perform:

• An open loop design first mindset (no buffers unless absolutely necessary and avoid zoning)

• Resistance, Pressure Drop and the Index Circuit

• Pipe sizing based on the heat requirement

• Flow rates & velocities

• Pump head maps

• Room-by-room and whole house heat loss calculations

• Air Changes (not accepting defaults)

• System water quality (VDI 2035)

If an installer can walk you through these with confidence, you’ve likely found someone who can design a system that genuinely works.

Don’t be afraid to ask these sort of questions.

Look for useful certifications from the likes of Heat Geek Training, Warmur Academy (Hydronics Unlocked), or Mario Dodic HVAC Education Hub.

This isn’t an exhaustive list, but I know these providers teach the core design principles discussed throughout this article.

💡 Tip: If your installer has invested in this kind of training, it’s a strong sign they understand how to design and commission a heat pump system that will actually deliver.

For another perspective, this article by Simon Murray on Renewable Heating Hub highlights the same design red flags homeowners should watch out for — many of which align with the principles we’ve covered here.

Homeowners could also subscribe the Heat Geek Uninsulated YouTube channel for an understanding of the core concepts.

And subscribe to the Urban Plumbers YouTube channel where Szymon Czaban showcases how super efficient can be installed in homes of any size and age.

As Mark Allison of Powersonic Electrical and Sam Featherstone of Oval Renewables said on their Renewables Podcast, “the installer is actually more important than the equipment.” They were talking about solar, but the same lesson applies to all renewables. Most modern kit performs similarly; the real difference lies in the knowledge, skill, and aftercare of the installer.