What you need to know about CoP and hot water
What is CoP?
CoP, or, to give it its full title, Coefficient of Performance, is a measure used to evaluate the efficiency of heat pumps. It’s a ratio of the amount of heat generated to the amount of work input required to achieve that heat. In simpler terms, it tells you how much heating you get for a certain amount of energy input.
The CoP of a heat pump is calculated by dividing the heat output in kW by the electrical power input in kW. So, if a heat pump has a CoP of three, it means that for every unit of electricity it consumes, it produces three units of usable heat energy.
So, why is CoP important?
It’s all about efficiency. It’s using the electrical energy you have available and multiplying that electrical energy into significantly more units of usable thermal energy.
If you take, for example, a direct electrical panel heater or fan heater, when you put one kW of energy into it, you’ll get around one kW of heat energy out – so it has a CoP of one. With a heat pump, however, depending on the efficiency of the system, you should get a CoP of three, or even four.
How can you achieve a good CoP?
A number of factors will affect the CoP of your heat pump.
First of all, it is worth talking to your heating engineer to see if your home would benefit from additional loft or wall insulation and double or triple glazed windows. Newer homes tend to already have good insulation as they would have needed to comply with more stringent legislative standards. However, older homes may benefit greatly from extra insulation before a heat pump is installed.
Once any remedial work has been completed, the next important stage is for your heating engineer to carry out the heat loss calculation for the building. This includes measuring each room and assessing the doors, windows, roofing, insulation and fabric of the building.
The heat loss calculation will help them calculate the size of heat pump required and the size and area of the heat emitters that will be needed, whether that’s radiators, underfloor heating, a heated skirting board option such as ThermaSkirt, or combination of these. It is worth remembering that a heat pump system operates at much cooler flow temperatures than a traditional gas boiler, so radiators etc are unlikely to feel so hot to the touch.
Unlike replacing a gas boiler, which can be over- or undersized without causing a significant problem, a heat pump needs to be correctly sized for the system, or it won’t work efficiently.
The CoP of the heat pump is heavily linked to the efficiency of the system so you need to ensure that the whole system is firstly designed correctly for the property type, and then installed correctly, in accordance with the design.
How to ensure efficient hot water
Hot water is also very important. A demand for hot water may make the heat pump run at a higher temperature, but that can be mitigated by selecting the correct cylinder. The Mixergy cylinder has an external plate heat exchanger, which generates hot water more efficiently than a cylinder with an internal coil, helping to achieve the best possible CoP. The Mixergy cylinder is also compatible with solar PV, which can be used to heat the water, making the system even more energy efficient.
Once the system has been installed and commissioned, the CoP can be monitored using the heat pump controller or an app.
It’s worth noting that the CoP can vary throughout the year, depending on factors such as outdoor temperature, indoor temperature, and the specific design and efficiency of the heat pump system. The measurement which shows the efficiency of the system throughout the year is the Seasonal Coefficient of Performance (SCoP) or Seasonal Performance Factor (SPF).
How to source Mixergy for your heat pump install
Mixergy is as simple to install as a conventional cylinder. We have a wide network of Mixergy Approved Installers who we’ve trained ourselves. To get a full quotation for the cylinder and installation, please contact one of our Installers who advise on what’s right for you.
