Explaining your heat pump savings figure

How we've calculated your potential savings from a switching to a heat pump from a gas boiler

The figures we've shown you are based on your actual energy usage from the last year and are designed to give you a ballpark estimate of how a heat pump could benefit your home.

What we've included

Your winter solar export earnings

We've taken your actual annual exported energy and assumed that 20% of this was generated in heating season months (October-March). We’ve assumed just 20% to be on the safe side - you can check out this blog from Good Energy for more information on solar panel output in different seasons.

With this figure, we’ve valued it at the current export rate of 15 pence per kWh (as of March 2026). This is the revenue you would have received from exporting that solar energy back to the grid.

Your estimated heating and hot water costs

We've used your estimated annual gas usage (as shown on your bill) and your current gas unit rate and standing charge to calculate what you're spending on heating, hot water, and cooking. We've excluded the 2% of gas usage that can go to cooking appliances (like gas hobs) to focus on heating and hot water costs.

Your estimated heat pump costs

We've modelled what your heating and hot water costs would be if you switched to a heat pump, using the Cosy heat pump tariff as a reference point. This assumes you would use your winter solar generation to offset your heat pump running costs, rather than exporting it to the grid.

Your potential profit

This is the difference between your heat pump costs and your winter solar earnings. A positive figure means you could offset your entire heating and hot water costs with solar generation and have profit left over. This also assumes you wouldn’t need to pay a gas standing charge, because with a heat pump you’d switch away from gas entirely.

Important assumptions and limitations

• These are estimates and averages, not your exact costs. Actual savings will depend on factors including your home's insulation, how you use heating, weather patterns, and future energy prices.
• The calculations assume you would use 100% of your winter solar generation to offset heat pump costs (rather than exporting to the grid). Your actual usage may vary.
• This analysis does not include: the cost of installing a heat pump, maintenance costs, or any government grants or incentives you may be eligible for.
• Energy unit rates and standing charges may change, which will affect your actual costs and savings.
• We've used the Cosy heat pump tariff as a reference point. Your actual heat pump running costs may differ depending on which tariff you choose.
• These figures are based on last year's data and assume similar energy usage and weather patterns going forward.

Data assumptions:

• The calculations assume you would use 20% of your annual Solar generation to offset heat pump costs (rather than exporting to the grid). Your actual usage may vary.