Heat pumps in depth — types, COP and SCOP
Same cycle process as a cooling system but used to heat up — and a rapidly growing trade
A heat pump uses exactly the same cycle as a cooling system — compressor, condenser, expansion valve and evaporator — but the purpose is reversed. Instead of removing heat somewhere to create cold a heat pump extracts heat from the surroundings (air, ground or groundwater) even when they are cold and releases it as useful heat for heating and hot water. This is why a skilled cooling technician can relatively easily specialize in heat pumps — the basic technology is the same you have already learned.
§The most important types of heat pumps
- 01Air-to-water
- 02Air, cooling and exhaust
- 03Ground source and liquid-to-water heat pumps extract heat from soil or groundwater where temperature is more stable throughout the year.
- 04Hybrid solutions: combine a heat pump with another heat source, such as an existing oil boiler, for the coldest days.
§COP — the snapshot
COP (Coefficient of Performance) is the ratio between the heat the heat pump delivers and the electricity it uses to deliver it measured at one specific combination of outside and supply temperature. A COP of 3 means the heat pump delivers three times as much heat energy as it uses electrical energy. COP is useful for comparing systems under identical conditions but it doesn't say much about how the system performs over a whole year with changing weather.
§SCOP — the season's average
SCOP (Seasonal Coefficient of Performance) on the other hand is a weighted average of the heat pump's efficiency over a full heating season calculated according to the European standard EN 14825 with fixed climate zones and standardised assumptions about outdoor temperature and duration. Because SCOP takes into account that a heat pump performs differently on a frosty January day than on a mild autumn day it gives a far more accurate picture of what the system will actually cost to operate over a year than a single COP figure does.
§What affects efficiency in practice
The smaller the difference between outside and inlet temperature, the easier the work for the compressor, and the higher the COP and SCOP become. This is why underfloor heating (low inlet temperature) suits heat pumps particularly well, while old radiator systems with high inlet temperatures require either larger units or renovation of the heat distribution to provide good efficiency. Correct sizing, the right amount of refrigerant and a well-adjusted expansion valve are just as crucial for a heat pump's real efficiency as they are for a regular cooling system.
§Heat pumps and your career
Because heat pumps are a cornerstone in phasing out oil and gas heating in Danish homes and buildings, there is large and growing demand for technicians who understand both the cooling circuit, electrical installation and the building's heating system. This makes the heat pump field one of the most obvious specialisations to build on top of your apprenticeship as a cooling technician — you do not start from scratch, you build directly on what you already know.
“A heat pump does not lie about how good it is — only a single COP figure taken out of context does.”