Solar Panels vs Heat Pump Energy Output Calculator

How this calculator works

This calculator works in ranges rather than single figures, because real quotes, yields and tariffs genuinely vary that much. It starts from typical UK price, output and savings ranges drawn from published 2026 industry guides and official scheme documentation, then scales them by the quantities you enter and adjusts them for each choice you make below. The result is a low-to-high band that a realistic outcome is likely to fall within, not a promise of the figure you will achieve.

A typical 4 kWp solar array generates around 3200 to 3800 kWh of electricity a year, while an air source heat pump on a medium UK home delivers roughly 9000 to 14000 kWh of heat, drawing about a third of that, some 3000 to 4700 kWh, as electricity thanks to a coefficient of performance around 3. The numbers are not rivals: solar produces energy, the heat pump consumes it to move heat indoors, so the honest framing is generator versus efficient consumer rather than either-or.

Home size

Home size scales both figures: a larger home has more roof for solar and, more significantly, a bigger heating demand for the heat pump to serve. The comparison assumes a typical 4 kWp solar array on a medium home, scaled up or down, and a correctly sized air source heat pump meeting the home’s space heating and hot water demand.

Region (solar resource)

The same panels generate more in Cornwall than in Caithness. The industry baseline is around 850 kWh per year for every kWp installed on an unshaded south-facing roof in an average UK location, with southern England running around 5 percent above that and Scotland 10 to 15 percent below. The calculator scales its output and savings figures accordingly.

What else affects the figures

Financially the two answer different questions: solar cuts electricity costs and earns export income with payback around 8 to 11 years, while a heat pump replaces a boiler, with the Boiler Upgrade Scheme grant cutting a typical to installation to to and running costs that depend on the electricity-to-gas price ratio and the installation quality. They pair unusually well: heat pump demand raises solar self-consumption, especially with a battery, and summer solar runs the heat pump’s hot water essentially free. If a household can only fund one, the usual guidance is to fix insulation first, then choose solar for bill reduction on a sound heating system, or the heat pump when the boiler is due for replacement anyway.

Certification, planning and grid connection

If a calculation here prompts a project, the practical next step is an MCS-certified installer’s survey: MCS installers must provide a location-specific generation estimate using the standard industry methodology, which turns the broad ranges on this page into a figure for your actual roof. Most domestic solar work falls under permitted development, with the usual exceptions for listed buildings, flats and conservation areas, and installations must be notified to the district network operator under the G98 or G99 procedures, which a competent installer handles as part of the job.