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? The charts below show cumulative emissions and cost. This is only an estimate as the model is fairly simple. 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. If you expect to use power from your own solar PV panels, use the Solar estimator below to see how much difference this can make.


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

Your overall GHG savings and costs over the period.

When Carbon (t CO2e) Cost (£)
  Current Electric heating Difference Current Electric heating Difference
Diesel C EV C   Diesel £ EV £  
Annual * Diesel 1 EV   Diesel 1 EV  
Total Diesel EV Difference Diesel EV Difference
* For carbon, the annual emissions are for the first year only as electricity gets cleaner over time.

Edit these assumptions for your situation

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

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.

If you go off gas completely you no longer pay this fixed charge. If you do not intend to disconnect from the gas, set this field to zero as you will not be able to make these savings.

Enter year 0 for now, enter 100 for never.

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.

Your low carbon replacement

A heat pump should be at least 300% efficient.

If you have a solar PV array, estimate the proportion of charging electricity you will be able to use for this here.

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

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.

The GHG emissions factors are xxkg/kWh xxkg/kWh 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.

Solar Estimator

Enter your parameters to estimate how much of your heating energy could come from your solar PV panels.

You do not have any solar panels

Estimated current import and export:
0 kWh import from the grid (your electricity bill)
0 kWh export to the grid

Our best estimate is that you could obtain 0% of your heating electricity from your PV array.

To use the estimated value, enter 0 below. If you think this is incorrect, enter your value here. However the maximum based on your export is XX%

Solar power assumptions

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

Please enter your typical export in kWh/month

Ok - we will estimate from your array size and your own use

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.

We need to estimate how much of your solar power you are already using but this is not measured directly. If you know your bill, please adjust these values until the estimated import (right) is reasonably close to your bill. Within 10% is about as good as you can expect.

This includes your self consumption from your solar PV. As a first guess, try your annual bill kWh (what you draw from the grid) plus a third of your annual generation.

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

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.

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.

Hot Water - to estimate how much of your gas bill is for hot water rather than heating

If you take baths, count a bath as two showers

Assumptions behind the solar calculations

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  • 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