Getting a heat pump or other electric heating

How much can you reduce your greenhouse gas emissions (GHG) by switching from your oil or gas boiler to a heat pump or other low carbon heating system - how much will this cost?
Introduction This tool is based on a simple model and the results are only an estimate. Even so there are many factors to consider and you can modify most of the assumptions for your situation - apart from the GHG emissions of the fuels.
Current and replacement heating
  • Your current heating system   
  • 12000 kWh/year is typical but it depends on the size of your home and how well it is insulated.

  • 1000 litres/year is typical but it depends on the size of your home and how well it is insulated

  • Your low carbon replacement     
  • If you go off gas completely you no longer pay the fixed charge.

  • Enter year 0 for now, enter 100 for never.

Results summary

For a more accurate estimate, edit the additional assumptions (below or right)

  • You replace your   with  .
  • It uses   kWh/year.
  • You get  % of the electricity for heating from your solar panels.
  • Your annual heating bill will be £  compared to £ .
  • Over   years you save   tonnes carbon.
  • Your initial cost is £ ; overall net   of £ .

For comparison, the average UK resident emissions is 8-12 tonnes/year depending on how you measure it.

GHG emissions graph
GHG emissions table (tonnes CO2e)
When Current Electric heating Difference
Initial/replacement Diesel C EV C  
Annual emissions * Diesel 1 EV  
Total emissions (  Diesel EV Difference
* The annual emissions from electricity decrease over time.
Costs graph
Costs table (£)
When Current Electric heating Difference
Initial/replacement Diesel £ EV £  
Annual energy bill Diesel 1 EV  
Total cost ( ) Diesel EV Difference

Additional assumptions

  • A condensing boiler should be 90% or more when new but could be 70% if it is not working well.

  • A condensing boiler should be 90% or more when new but could be 70% if it is not working well.

  • A heat pump should be at least 300% efficient.

  • Heat pumps deliver heat more slowly so you need to maintain some heating even overnight, in order to achieve the required morning temperatures. This increases overall demand. See also Are you heat pump ready (Transition Cambridge)

Energy prices
  • If you go off gas completely you no longer pay this fixed charge.

Upfront costs
  • Under the Boiler Upgrade Scheme (BUS) you should get a £5000 voucher from the government so take that off the price

  • This could be oil filled radiators or electric panel heaters with an instant water heater, or an electric boiler

  • This could be room storage heaters and a hot water cylinder with immersion heater, or an electric storage boiler system

Upfront GHG emissions
  • There is limited data, because it is a small part of the lifetime emissions.

  • There is limited data, because it is a small part of the lifetime emissions.

  • A small heat pump e.g. 6 kW could be less - say 2000. A large heat pump e.g. 16 kW could be 5000. The refrigerant that circulates the heat is (currently) a large part of the embodied emissions and the amount required varies with the heating capacity. Lower carbon refrigerants should be more common soon.

  • There is very little data on this - say 30-100 kg each plus 200kg for the hot water system

  • Basic storage heaters could be as little as 50 kg each. An electric storage boiler could be 2000 kg or more - there is very little data available on this.

Solar PV panels
  • Estimation method

    If you know your typical monthly export by month then we can use that. Otherwise we can estimate it less accurately

  • If you do not know, multiple your array size in kWp by 800. So if you have a 4 kWp array try 3200.

  • This is the usable kWh, which may be less than the nominal capacity.

  • If you have a solar array at home with an export meter and you get paid for your measured export, enter the export tariff here. This is the cost to you of using your own electricity.

  • More solar assumptions
    • You do not have any solar panels

    • This is the average over the year and it includes everything that you do not export to the grid. So if you have a battery, this includes losses in the battery.

    • Many homes use more electricity in winter than in summer - for example you use the tumble dryer more in the winter

    • Using your own solar power or taking it from the grid makes no difference to overall carbon emissions, because your solar panels are effectively part of the grid and they generate whether you need power or not. If you prefer you can treat your solar power as zero emissions.

    • For estimating hot water use:

    • If you take baths, count a bath as two showers

  • Solar chart

The GHG emissions factors are xxkg/kWh (standard) xxkg/kWh (offpeak) for electricity, xxkg/litre for gas and xxkg/litre for oil. These factors include upstream emissions for fuel and and transmission losses for electricity. Carbon emissions from electricity reduce by xx% each year. Inflation has not been taken into account.

See Assumptions and data sources for background on these default values.

  • The yield from your solar panels varies over the year according to the season and weather. We have used figures for the East of England.
  • If you do not know your export we estimate your self consumption based on monthly electricity use, solar power yield and battery size according to the standard method used in SAP 10 - an update of the method currently used to calculate the Energy Performance Rating of your house. From this we calculate your monthly export.
  • For charging a car, or for use of stored heat, we assume that all this exported energy is available for charging, on a day to day basis. I.e. the amount used for charging is either the daily requirement or the daily export, whichever is the smaller.
  • For other applications we assume that only a proportion of this energy is available for use and a proportion of the demand can be met, because of misalignment between the demand and the available power. For example, space heating is needed mainly in the mornings and evenings when there is little if any sun, and the power generated during the day may be more than is required at that time. This is less of a problem if you are using a battery but it still applies as the battery is of limited size. The estimate is rather crude and not as reliable as a professional estimate with more information to work on.

For more detail see References