Compare heat pumps

How can I compare the consumption of different heat pumps for my situation? In this blog I explain more about this and you get useful tools to distinguish between different heat pumps.

First of all, it is important to know what COP is and what it actually stands for.

COP is the abbreviation for Coefficient of Performance and indicates how efficiently a heat pump uses energy in one specific situation.

An example for an air-water heat pump:

The COP of an air-water heat pump is always specified at a certain outside temperature and at a certain temperature of the central heating water heated by the heat pump.

Suppose the COP is 5 at an outside temperature of 12 degrees and a central heating water temperature of 30 degrees. Then the heat pump produces 5 kWh of hot water with 1 kWh of electricity.

However, in a different situation, the COP of this heat pump will be different.

For example, the COP can be 4 at an outside temperature of 2 degrees and a central heating water temperature of 35 degrees.

In practice, a heat pump never runs in just one situation.

During a heating season, the outside temperature is mainly between -10 degrees and 16 degrees. But also the central heating water temperature is (usually) not constant.

When it is freezing outside, the central heating water will be warmer than when it is 12 degrees outside.

Compared to another heat pump, one heat pump can be more efficient in one situation, but much less efficient in another situation.

So the COP doesn't really say much.

You cannot use it to compare heat pumps and you certainly cannot use it to determine the expected consumption.

It is more important than the COP to know how efficient a heat pump is over an entire heating season. That's what the SCOP is for, the Seasonal Coefficient of Performance.

How many kWh of heat energy must a heat pump produce in an entire heating season and how much kWh of electricity does the heat pump consume for this.

If you know the SCOP of heat pumps for your situation, you can compare them well on energy efficiency, but you can also calculate the power consumption properly.

The SCOP and therefore the consumption of a heat pump for your situation mainly depends on three factors:

the climate in your region,

the required central heating water temperature to comfortably heat the house in case of severe frost

and the maximum power of the heat pump compared to the required power.

Nowadays it is mandatory for heat pump manufacturers to state a standardized SCOP of each heat pump.

This makes it easier to compare them.

To keep it simple, 3 climate zones are used, namely

cold (climate in Helsinki), medium (climate in Strasbourg) and warm (climate in Athens).

The Netherlands comes closest to the average climate (Strasbourg).

Yet there are differences between the climate in Strasbourg and the climate in the Netherlands.

For example, in Strasbourg it is less than 5000 hours a year colder than 16 degrees, while in the center of the Netherlands it is 30% more, namely about 6500 hours.

Another difference is the number of freezing hours, which is double in Strasbourg compared to the center of the Netherlands.

We can therefore best calculate the SCOP depending on the climate in the Netherlands.

However, there are also considerable differences between the various regions in the Netherlands.

For example, the number of frost hours in the east of the Netherlands is 50% higher than the number of frost hours in the west of the Netherlands.

To be able to really compare and to know the expected power consumption, the SCOP must be calculated on the basis of the climate in your region.

Another important factor for the SCOP is the required temperature of the central heating water. The standardized SCOP is often stated with two central heating water temperature profiles, namely the 55 degree profile and the 35 degree profile.

55 degree profile

It is assumed that if it freezes -10 degrees outside, the central heating water must be 55 degrees in order to heat the house properly.

35 degree profile

It is also assumed that if it is not so cold, the heat pump can heat the central heating water to a lower temperature to keep the house pleasantly warm. If it is 12 degrees outside, the profile indicates that the central heating water temperature must be 30 degrees.

If the SCOP is specified for the 35 degree profile, the central heating water temperature will be 35 degrees if it is -10 degrees outside. If it is 12 degrees outside, the profile indicates that the central heating water must be 24 degrees to keep it pleasantly warm inside.

But which central heating water temperature profile should you take, that of 35 degrees or that of 55 degrees? Or another profile?

There are major differences in the efficiency of heat pumps between the two profiles, and therefore also major differences in power consumption.

That is why it is important to know what the central heating water temperature profile of your home should be, in particular how warm the central heating water should be to properly heat your home at -10 degrees.

When it gets colder outside, the central heating water temperature must become increasingly warmer in order to be able to heat with sufficient power, and therefore more power.

Because the price of heat pumps increases with higher heat pump capacities, people often opt for a heat pump with a somewhat lower capacity.

If more power is required than the heat pump can supply, an additional energy source is required to supply the shortfall in power.

Given that the number of hours with severe frost* in the Netherlands is limited, the additional energy source only needs to be used to a limited extent.

There are two options for an additional energy source:

Hybrid: In a Hybrid system, there is still a gas boiler present, which is primarily intended to heat tap water.

The gas boiler can also be used to make up for any power shortage of the heat pump. The part of the power and energy that the heat pump cannot supply is not included in the SCOP calculation.

All-electric: With an All-electric system, there is no longer a gas boiler.

Everything is electric. So if the heat pump cannot supply the required power, the shortage will be supplemented with an electrical element. The current used by this electrical element is included in the SCOP calculation.