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Air Source Heat Pump Sizing Calculator UK

Find out what size heat pump system you might need using this quick heat pump size calculator from Heat Pumps UK.

Our handy tool will provide you with an estimated size for a new air source heat pump system based on the size of your property (using the number of bedrooms as a guide) and how well insulated it is.
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CALCULATE HEAT PUMP SIZE

Heat Pump Size Calculator

Air Source Heat Pump Size Calculator

Select Number of Bedrooms (1-2, 3, 4 or 5+) and How Well Insulated (Well insulated or Poorly Insulated) Your Home Is:

Your air source heat pump size should be 0kW

*size estimates are a guide only, and can change depending not only on the levels of insulation, but also other factors including number of people in the household and the demand for heat and hot water.

Heat Pump Sizing Calculations

Calculating the size of a heat pump is more straightforward for modern properties as these will have been built with levels of insulation that meet UK building regulations and therefore the property could be classed as ‘well insulated’.

Older buildings are likely to be less well insulated, and may be solid wall construction, so do not even have wall cavities to fill, which would lead them to be less efficient and therefore potentially in need of a larger heat pump system. A poorly insulated house with non-existent insulation, or minimal insulation levels, will usually require some insulation upgrades prior to heat pump installation to minimise heat loss and running costs.

Any heat pump company estimating the size of air source heat pump system required should take into account some of the following:

  • Existing levels of insulation or levels of insulation if you plan to upgrade
  • Existing radiators and/or underfloor heating
  • Size of the property
  • Number of rooms and their uses
  • Seasonal fluctuations in temperature (air source heat pumps are more affected by this)

 

How much does heat pump size matter?

Heat pump size is important as without a system of sufficient capacity you will struggle to meet your demand for heat and hot water. If the capacity is too low, the heat pump will be having to run for extended period to meet demand, and this will reduce the lifespan of your heat pump.

Alternatively, if you install a heat pump that is well over capacity and too powerful for your household’s heating demands, then the system will be ‘short cycling’ — effectively turning on an off frequently — which will put the heat pump under unnecessary strain.

  • A typical air source heat pump in a well insulated 3-bedroom property of around 100 square metres would need to be in the region of 5kW to heat the property effectively.
  • If the floor space of a property was double that, at 200 square metres, it is fair to assume with other things being equal that a heat pump in the region of 10kW would be required. 

 

What difference does the type of heat pump make?

The size estimates we suggest above are specifically for air source heat pumps as these are the most common and likely to be what will be suitable for the majority of properties. Air heat pumps are impacted more by seasonal changes in temperatures, so if you live in an area that experiences large fluctuations in the colder months, you may need a system with a larger heat pump capacity.

Ground source heat pumps are less impacted by seasonal changes in ambient temperatures as ground temperatures remain largely the same throughout the year. This means if a 5kW air source is recommended, where a ground source heat pump is also possible, the recommended size might be 4kW.

Are free grants available to help with the cost of heat pump installation?

The size of the heat pump recommended for your home will have an impact on the cost. Generally, if you have a larger home and household, the bigger the heat pump system you will require, and this will be reflected in the price.

While the costs may at first be off putting — if for example, you compare it to the cost of installing a replacement boiler — but the long-term savings and reduced carbon footprint will more than prove worthwhile. The good news is that there is funding available to help households make the switch to an energy efficient renewable heating system. 

The Boiler Upgrade Scheme provides air source heat pump grants up to £7,500 to households in England and Wales to install heat pumps and other energy efficient heating systems. Those in Scotland may be able to get a Scottish Government grant up to £7,500 (or £9,000 if they qualify for rural uplift funding) or an interest-free loan, while some funding grants are also available in Northern Ireland.

You don't need to be claiming benefits!

Find the best heat pumps for your home.

Contact us today to find out about air source heat pumps and whether they are a suitable option for your property. We will put you in touch with expert installers who will help you ascertain which heat pump system is best for your home

Through our help, you’ll be on the way to saving money, boosting energy efficiency, and reducing your carbon footprint. Make the first step on the road to a greener future and find out what an air source heat pump system could do for you.

Join thousands of happy customers who have switched with us.

Tony Renaud
We had an Ideal Logic 2 Combi boiler fitted on 29/06/23 with Fixx. Craig the Engineer arrived bright and early after a call to say he would be there in 30 minutes. He was very efficient and finished by mid afternoon before running through all the wireless thermostat details before leaving. Found the company extremely helpful with any questions I asked, great company to do business with and would recommend highly.
Eduardo Benito
Extremely impressed with Fixx and everyone there that I dealt with. They discussed all the requirements for a new under sink water heater for my flat to supply the kitchen sink and bathroom sink in the next room, as well as connections for a dishwasher and washing machinke. They provided a quote very quickly and the whole thing was installed just a few days later. Very neat setup, all ready for the kitchen fitter to complete the worktop and hook up the taps to the sink (see photos). I would 100% use Fixx again - I'm a very satisfied customer.
Simon Richards
The two gentlemen from Fixx did a fabulous job removing my Boiler Mate 2000 and replacing it with an unvented cylinder. Everything at each stage was explained to me and they worked extremely hard to achieve a fantastic result. I won’t hesitate to contact them in the future if and when I need a new boiler and would 100% recommend Fixx to anyone.
Raluca Badea
Very pleased with Fixx services, from start to finish. Craig kindly arranged for my Baxi Duo Tec boiler to be repaired asap and the engineer (Louis) arrived on time, was professional and polite, talked me through what he found and how he fixed it. Highly recommend! Thank you Fixx.
Phil Smith
I've a contract for my boiler so when I found a leak, I contacted the helpline. Still had hot water but they still sent someone within 24 hours. Engineer (Darren) came and found the fault. Had the correct part in the van and heating was back on in around an hour from his arrival. Great service and knowledgeable. Highly recommend.
Ian Edwards
Great service. Carl, the plumber, who sorted the boiler was so friendly and knowledgeable. So good in fact that we got the company to send him again to fit a Hive system which has helped us save a fortune.
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