ᐅ Estimating Electricity Consumption with a Heat Pump

Hello,
we are planning to build soon, and I am currently looking into the heating system.
I have tried to estimate how much electricity our air-to-water heat pump might consume.

Am I correct in understanding that the final energy demand is the amount of energy I need to put into the house for heating and hot water?
And this can be provided by oil, gas, or a heat pump?
If so, how does the COP work in this context?

I am trying to explain it with a very simple, hypothetical example:
A house with 200 sqm (2153 sq ft) and a calculated final energy demand of 10 kWh/sqm/year.
I understand this to mean that 2000 kWh of heating energy is needed annually.
An air-to-water heat pump with a theoretical COP of 2 converts 1 kW of electricity to 2 kW of heat.
Does that mean that with such a heat pump, only 1000 kWh of electricity is needed for heating and hot water?

I hope I am not making too many mistakes, but primary energy, final energy, COP, efficiency, and performance are all new and quite confusing to me.

Thanks in advance
Anja

a-stern.1 schrieb:
A house with 200 sqm (2,150 sq ft) and a calculated final energy demand of 10 kWh/sqm*a (10 kWh/sq ft*yr). I understand this to mean that 2,000 kWh of heating energy is needed per year.

Final energy demand already includes distribution losses, etc. Useful energy is what you actually need in the living space to maintain or reach temperature x.

a-stern.1 schrieb:
An air-to-water heat pump with a theoretical COP of 2 converts 1 kW of electricity into 2 kW of ‘heat’. Does that mean such a heat pump requires only 1,000 kWh of electricity for heating and hot water?

Exactly. However, the COP is determined only under specific test conditions. The actual ratio of heat output to electricity input over a whole year is the real seasonal performance factor (SPF). For such a well-insulated new build combined with an air-to-water heat pump, the SPF should be at least 4. So, for your 2,000 kWh of heat energy, you’d need 500 kWh of electricity. Be sure to exempt yourself from the ERR obligation and do not install a buffer tank for the heating system. It only reduces efficiency and increases initial costs.

Hello and thank you very much for the response.
I still need to read up on ERR, but it seems that I have understood the electricity part correctly.
Although, as I understand it, 10 kWh/m²·a (10 kWh/sq ft per year) might even be a bit too high.
I just find it hard to believe that the electricity consumption is really that low, but I am looking forward to it.

The math is the easy part. More challenging is estimating your annual performance factor and also figuring out how much extra energy you will need in the first few years to dry out the construction moisture.

And if you are seriously aiming for around 10 kWh/m² (10 kWh/sq ft), I would skip the underfloor heating and use infrared or ventilation heating instead. At that level, you are already in passive house territory and only need heating on the coldest days.

The 10 kWh/m²·a (10 kWh/m²·a) figure comes from a model home by the provider. Whether this will actually be achieved remains to be seen. However, it is offered as KfW 40+.

I don’t need exact numbers right now; I’m more interested in a bit of certainty. So far, we have district heating and will switch to electric heating in the future... which makes us quite concerned about the electricity bill. Whether it ends up being 500 or 1,000 kWh (538 or 1,076 kWh) doesn’t matter much, but I would like to know if it’s 1,000 or 10,000 kWh (1,076 or 10,760 kWh).

At 10,000 kWh (10,760 kWh), that would be about 5,000 €.

And then there’s the photovoltaic system, about which I have no idea how much it will generate, how much we will consume ourselves, and so on.

But thank you again for the help.

The EH40 standard has a limit of 25 kWh/m² (2.3 kWh/ft²). A building is considered a passive house from around 15 kWh/m² (1.4 kWh/ft²). Therefore, 10 would be an exceptionally good value. It seems someone has definitely mixed up the numbers.