I work for a home energy monitoring company (alertme.com). We're working on a way to estimate the energy usage of a fridge using only the aggregated signal. In terms calculating when the fridge is on and when it is not on the algorithm is doing very well. However, estimating the power usage of the fridge when it is on has been problematic.

What I want to know is if there are standard set of compressor motors that are used in domestic refrigerators. So far I've noticed only 80W and 120W compressors, the majority being 80W. Would it be correct to assume that there standardised compressors? And if so, what range of compressors are there? (eg. 80W, 120W and 160W).


If you want to know why I want to know this then read on.

The problem relates is that we only measure apparent power (The current induced in an iron core clipped around the live or neutral cables that feed into your power meter). We do this as it makes the kit cheap to make and allows the user to install the kit without needed to call out an electrician.

What the meter reading measures is real power -- there is a linear relationship between real power and apparent power is linear. But this relationship changes depending on the load. What we've observed is that if the fridge turns on when there is a more capacitive load (TVs, computers, etc...) then the increase in apparent power is less than what the fridge is actually using. Whereas, if there is a more resistive load (heaters, cookers, etc...) then the apparent power increase is higher than what the fridge is actually using.

So I'm hoping that compressor motors have a small standardised set of power ratings and not bespoke for each fridge or manufacturer. That way I can quantise the fridge powers my algorithm is producing eg. my algorithm measures a 95W load then that gets interpreted as a 80W compressor rather than a 120W compressor.

Thanks for any information anyone can provide.