The carbon maths
A boiler and a heat pump do the same job, so compare them per kWh of heat delivered to the building, not per kWh of fuel:
- Gas boiler: gas kWh × 0.18231 kg CO2e per kWh (2026). A boiler turns only part of the gas into useful heat, so each kWh of heat costs more than one kWh of gas.
- Heat pump: heat needed ÷ SCOP = electricity kWh, × 0.13096 kg CO2e per kWh (2026). The SCOP, or seasonal coefficient of performance, is how many kWh of heat the pump delivers for each kWh of electricity over a year.
With a boiler that is 85% efficient, each kWh of heat from gas carries 0.21448 kg CO2e. Grid electricity is 0.13096 kg per kWh, so in 2026 even plain electric heating would be about 39% lower carbon than the boiler. A heat pump then divides the electricity needed by its SCOP. This wasn't always so: in 2019 the factors were 0.18385 for gas and 0.2556 for electricity, so plain electric heating was higher carbon than gas, and a heat pump needed a SCOP of at least 1.2 just to match the boiler. The cleaner grid is why the case is now so strong.
A worked example
An office uses 60,000 kWh of mains gas a year, as shown on its bills. Assume the boiler is 85% efficient, so the building needs 51,000 kWh of heat. These are example figures: your heating engineer can estimate yours.
| Heating | Energy used | kg CO2e (2026) | Cut |
|---|---|---|---|
| Gas boiler (Scope 1) | 60,000 kWh gas | 10,939 | |
| Heat pump, SCOP 2.5 (Scope 2) | 20,400 kWh electricity | 2,672 | 76% |
| Heat pump, SCOP 3 (Scope 2) | 17,000 kWh electricity | 2,226 | 80% |
| Heat pump, SCOP 3.5 (Scope 2) | 14,571 kWh electricity | 1,908 | 83% |
At a SCOP of 3, the office's heating falls from 10.94 to 2.23 tonnes a year, a saving of 8.71 tonnes. Since 2019 the government's electricity factor has fallen by about 49%, while the gas factor has barely moved, so if the grid keeps getting cleaner the saving grows each year.
What about running costs?
Using the government's 2025 average business prices, 8.29p per kWh for gas (for firms buying under 278 MWh a year) and 29.1p per kWh for electricity (for firms buying 20 to 500 MWh a year), both including the Climate Change Levy and excluding VAT, the example office would pay about £4,974 a year for gas and about £4,945 for the heat pump's electricity. Roughly the same. Your own unit rates matter more than averages, so run the numbers with your bills: cost of heat from gas = gas price ÷ boiler efficiency; cost of heat from a heat pump = electricity price ÷ SCOP.
The Boiler Upgrade Scheme
Businesses in England and Wales can get a grant through the Boiler Upgrade Scheme if they:
- own the building, including one they rent out;
- are replacing fossil fuel heating, such as gas, oil or LPG;
- install a system of no more than 45 kWth, or 70 kWth where several heat pumps are installed together.
The grant is £7,500 towards an air-to-water or ground source heat pump, and £2,500 towards an air-to-air heat pump. Until March 2027 there is an extra £1,500 towards an air source or ground source heat pump where the property is heated by oil or LPG and has no mains gas connection. Hybrid systems that keep a gas boiler don't qualify. An MCS-certified installer applies to Ofgem for you and takes the grant off your invoice. Only the owner can apply, so if you rent, raise it with your landlord.
Don't forget the refrigerant
A heat pump runs on refrigerant, and any leak is Scope 1. If yours uses R32, its 2026 factor is 677 kg CO2e per kg, so a 1 kg top-up would add 677 kg CO2e in the year it happens. The gas type is on the unit's label. Keep to the leak check schedule and record any top-ups. Our post on refrigerant leaks explains how.
Reporting the switch
Your Scope 1 falls and your Scope 2 rises, so a reader comparing one scope at a time could misread it. In your Carbon Reduction Plan or SECR report, say when the heat pump went in and show the total alongside the scopes. If you are also cutting electricity with LED lighting or rooftop solar, those help offset the extra Scope 2.
How Carbon Recycling helps
Keep entering your gas and electricity bills and Carbon Recycling shows Scope 1 falling and Scope 2 rising month by month, each with the right year's government factor. Refrigerant top-ups go in by gas type as Scope 1. Add the heat pump to your Carbon Reduction Plan as a completed or planned measure, and the plan shows the effect against your baseline. Our free kWh to CO2e calculator lets you compare gas and electricity figures before you commit.