Your cooling and heating system normally account for much of your energy consumption at home. The amount of energy that you consume has a great impact on your electricity bills.

So when you’re buying a new system, consider the fact that the efficiency level of the unit that you purchased will determine the amount of money that you’re going to lose or save in the long-term.

All air conditioners and heat pumps come with specific energy-efficiency ratings. These help you measure, calculate, and determine the energy-efficiency of the unit. One of these energy-efficiency performance ratings is the so-called Coefficient of Performance (COP).

In formula, the Coeffient of Performance is the ratio of the power output to the power input of the system. It could be written as:

One thing to remember is that the Coefficient Performance helps you determine the efficiency of a system, especially if you’re purchasing a heat pump.

It is worth noting that air conditioners and heat pumps work through heat transfer. While the air conditioner removes heat from inside the room and exhaust it outside, the heat pump moves the heat from outdoors to indoors. In the case of a heat pump, the COP gives you an idea about the amount of heat that it generates in relation to the amount of energy that it has to consume to provide you with warm comfort.

Take note that watt is used as the unit of measurement for the input power and output power. That’s why the COP of a heat pump system is equal to the amount of heat produced for each watt of energy.

In theory, all of the electricity used (or power input) by the system gets converted into heat (power output). And we’re talking here of 100% energy conversion of the electric energy into heat energy. No energy losses whatsoever, that’s why we can say that a 1 watt of power used is equal to 1 watt of heat energy gained. Basically, it is a 1:1 ratio.

So, if you have a ductless heat pump, for example, with a COP of 4, it means it gives out 4 watts of heat for every watt of electricity consumed. Another way to put this is if the system uses 4 watts of energy to heat a space, all those 4 watts of electricity are 100% converted into 4 watts of heat energy which will warm the room.

The rule of thumb is, the higher the COP, the more energy-efficient the system is. It follows that a ductless heat pump air conditioner, for instance, with a COP of 11 is obviously way more energy-efficient than an electric heater with a COP of 1. What it says is that the former can generate 11 kW of heat for every watt of electricity that it consumes.

Remember that higher COP means lower electricity costs and higher energy-savings. In a heat pump system, a higher COP means more warm comfort for you but lesser energy consumption.