How is my CoP calculated?

Your CoP, or Coefficient of Performance, is a measure of how efficiently your heat pump is operating. It represents how many units of heat the heat pump produces per unit of electricity consumed. In the Passiv app, you can view your average estimated CoP on a year by year basis, as well as a breakdown of your average estimated CoP for each month in that year. To view this, open the Passiv app and go to the 'Analysis' tab at the bottom. Select the button on the furthest top right of your screen, which has a dial icon.

Why is the CoP estimated?

The CoP displayed in the Passiv app is calculated by the Passiv Smart Thermostat using data from the heat pump. However, different heat pumps provide different levels of data. For example some heat pumps provide both the instantaneous heat production and instantaneous power consumption for the device. From this, the Passiv Smart Thermostat can divide one by the other to calculate the CoP at that specific moment and then calculate an average over a given month. However, some heat pumps might only provide the heat production. This means the Passiv Smart Thermostat has to estimate the amount of electricity consumed based on the size of the heat pump, which may not always be 100% accurate.

Even for heat pumps which provide all the necessary information, the accuracy of that information varies. Therefore the values presented in the Passiv app are always estimated, as they are the most accurate values that we can provide with the data available to us.

Why is electricity consumption estimated?

For most of the fields and values used to optimise and report on your heat pump, the Passiv Smart Thermostat reads directly from the heat pump itself. However lots of heat pumps don't make their internally calculated electricity consumption available for third parties. When this happens the Passiv Smart Thermostat makes a best estimate based on other values. The Passiv Smart Thermostat will have some idea of the overall capacity of your heat pump - either set by the installer, set by you, or read from the heat pump itself. By comparing this with the command instructions sent down to the heat pump, the Passiv app can estimate the electricity consumption at any given moment.

For heat pumps that do provide their internally calculated consumption the Passiv app will still mark the values as estimated. This is because each heat pump provides their values at slightly different resolutions and accuracies. Passiv cannot guarantee the accuracy of any value read from the heat pump, as the Passiv app simply reports on what it receives.

What CoP should I have?

There is no hard and fast rule for what CoP your heat pump should be running at. Roughly, a well-operating heat pump will have a CoP of 3 or more. However there are a lot of other factors that impact the cost of running your heating. For example you might be on a time-of-use tariff. In this case, the heat pump might be using cheaper electricity at a lower efficiency. Although your CoP might be lower, the actual cost of your heating may be cheaper than if you were using more expensive electricity more efficiently.

My heat pump controller is giving me a different CoP.

On some heat pumps, the heat pump controller - usually situated close to the Passiv Programmer - will also provide an estimate of the current CoP. Often, this value is different to the value reported in the Passiv app. This is because the heat pump is able to calculate its CoP from raw data that it doesn't make available to third parties. This means the heat pump's CoP is likely more accurate, but the Passiv app's version should provide a good estimate.

If you notice that the CoP reported in the Passiv app is significantly different, it may be because the size of your heat pump is set incorrectly. To change your heat pump size, see How can I update my heat pump size?