Do heat pumps use a lot of electricity?

Do heat pumps use a lot of electricity?

This is a question I get asked a lot by my customers, and it’s a fair question, as nobody wants a bigger bill than what they started with using their existing fossil fuel energy supply.

Shift Towards Heat Pumps

Gas boilers are still the preferred choice in the UK, but more and more people are searching for alternative options to heat their homes.

Currently, a sensible alternative is heat pumps, among lots of other things.

Their popularity is growing in the UK, and it’s thought that they could become more popular than gas and oil boilers in the near future as insulation values increase in properties.

Efficiency Comparison: Heat Pumps vs. Boilers

It is true that heat pumps run on electricity; however, the important thing to remember is that heat pumps are a lot more efficient than even a modern condensing boiler.

Efficiency Breakdown

A modern condensing boiler can run at around 90% efficiency, whereas over a period of 12 months, a heat pump could easily reach 300% efficiency or more, depending on how well the system is designed and what it’s connected to.

Calculating Boiler Efficiency

An example of this would be producing 3 kW of heat from 1 kW of electricity used.

If you would like to know how efficient your current boiler is in percentage efficiency terms, type your boiler details into the database shown below and look for winter seasonal efficiency.

NCM-PCDB Search Database (Opens in new window)

This will show your boiler efficiency stated by the manufacturer for running your heating, which is the majority of your gas bill over a 12-month period.

If your boiler has an efficiency of 85%, it means for every 1 kW of gas input, you are only getting 0.85 kW back in useful heat; the rest is lost in the combustion process.

Considering Energy Efficiency

So, we know that heat pumps are more efficient, but still, it does not answer the question about electricity usage.

We were not overly bothered about this efficiency before, when fossil fuels were cheap, but now prices are changing rapidly due to world demand; it’s time to start thinking outside the box!

Estimating Running Costs

How much it will cost to run your new heat pump will depend heavily on how well insulated your home is.

The better the insulation, the smaller the heat pump will need to be to run your heating, and the cheaper it will be to run.

Performance Estimate Calculation

This is something we work out for you quite early in the process of designing your heat pump system.

As part of the MCS process, we are obliged to provide you with a performance estimate, which involves carrying out room-by-room heat loss calculations.

Then, inputting your current energy tariff information into a calculation tool, which works out the heat pump usage over 12 months based on the amount of ventilation heat loss you have in your property.

The running costs of the heat pump calculation also takes into account the desired air temperature of the rooms (usually 21°C) and how cold it is likely to get outside.

In the Southeast, this temperature is -2°C. These two parameters, plus the heat loss, are crucial to understanding the size of the heat pump and overall running costs.

The maximum flow temperature of the heat pump is also inputted into the calculation, as a heat pump working hotter is more expensive to run, but may be necessary to keep up with the heat loss.

The performance estimate is the magic document that doesn’t appear to be spoken about very often, but is there to protect the consumer, so all the facts regarding running costs are upfront before your gas or oil boiler is pulled off the wall, as there’s no turning back after that!

This is imperative to the heat pump design process and allows the customer to make an informed decision, not just about reducing carbon but also about a realistic outlook on what it’s going to cost in electricity going forward with higher tariffs.

Example Calculation

To show a rough example of heat pump usage over 12 months, I have put together an example below.

Please bear in mind that poor insulation values increase the amount of kilowatts required to heat your home.

The average usage for a typical home in the UK requires 12,000 kilowatt-hours for heating/hot water.

Using a Vaillant Aro Therm 10 KW heat pump at a flow temperature of 50°C, which is suitable for radiators as well as underfloor heating if sized correctly, has a seasonal efficiency of 3.85.

This equates to 385% efficiency!

So, at our new, silly electricity tariffs (only a guide based on current electricity prices when this post was written), I will use 35p per kilowatt-hour of electricity.

So, it’s simply 12,000 divided by 3.85 = electricity usage of 3116 kWh X 0.35p = £1090 per year running costs.

This calculation does not take into consideration the slight drop in efficiency when the heat pump is heating your hot water, but has taken this out to simplify the calculation.

The hot water is, of course, taken into account in the performance estimate PDF.

Fine-Tuning Efficiency

Please note – This is just an example to show the workings out, and the efficiency of heat pumps is also affected by good design and the flow temperature the heat pump is set at.

Running underfloor heating systems at a flow temperature of 35°C can boost the efficiency of this heat pump by up to 500%!

Vaillant Arotherm Plus Spec Sheet pdf (Opens in new window)

I hope this article has been useful. As always, please use the contact form if you are interested in a heat pump installation or want to increase the efficiency of your heating system in any way whatsoever.

We are here for free advice on your energy-saving journey.