Heat Pump Cycling Calculator
If your heat pump keeps starting and stopping, it’s probably cycling. A little cycling is normal, but frequent on-off behaviour can mean more wear, more noise, and poorer efficiency.
This heat pump cycling calculator checks whether your heat pump can modulate low enough for your home’s heat demand and predicts the outdoor temperature where cycling may start, particularly in mild weather.
If you want the full explanation, examples, and practical fixes, read the article: Heat Pump Cycling and Minimum Modulation.
This calculator forms part of my Heat Pumps Explained series, which covers how heat pumps work, how they’re sized, and how to interpret performance and running costs, including examples from my own 5 kW Vaillant aroTHERM heat pump installation.
Also check out further Free Heat Pump Tools and calculators.
Minimum Modulation Calculator
Tip: try minimum modulation presets 2.2 (3.5/5kW), 3.2 (7kW), 5.8 (10/12kW)
What this calculator tells you
This heat pump cycling calculator compares your heat pump’s minimum modulation output with your home’s heat loss and uses that relationship to estimate the outdoor temperature at which cycling may begin.
When minimum output is higher than demand, the heat pump cannot run continuously. Instead, it has to overshoot the target temperature or shut down and restart later.
What you’ll need
You’ll get the best results if you can provide:
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your heat pump’s minimum output (from the datasheet, installer information, or monitoring)
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an estimate of your home’s heat loss at your design outside temperature
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your design outdoor temperature (say -3C)
- an indoor target temperature
If you don’t have those numbers yet, the main heat pump cycling and minimum modulation article explains where to find them and how accurate they need to be for this check to be useful.
This calculator is a diagnostic starting point, not a full design or sizing tool.
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