Renewable Technology Payback Comparison

Solar PV and battery storage usually offer the shortest paybacks, but which of the two comes out ahead depends on your tariff. At this page's defaults (Octopus Outgoing 12p export, 40% self-consumption, an Octopus Go-style 7.5p off-peak rate and the Ofgem July 2026 cap) battery storage actually edges ahead of PV — roughly 10 years versus 12 — because the off-peak/peak spread is wide; on a higher export rate or with more self-consumption PV pulls level or ahead. PV payback depends heavily on your export tariff and how much you self-consume: the only legal requirement under the Smart Export Guarantee is that the supplier-set rate is above zero — there is no statutory minimum in pence, and some market rates are as low as around 4-5p/kWh. On a low export rate with modest self-consumption, PV payback can exceed 15 years; on a good fixed export tariff (e.g. Octopus Outgoing 12p, Good Energy fixed up to ~25p as of mid-2026) and higher self-consumption it falls into roughly the 8-13 year range, with battery storage typically 8-12 years on a time-of-use tariff. Air-source heat pump payback varies widely with achieved SCOP and the electricity-to-gas price ratio (see below) and ground-source has the longest payback because of its high installation cost. Always model your own quotes and tariffs rather than relying on headline figures.

Net Present Value (NPV) accounts for the time value of money — a pound saved in 10 years is worth less than a pound saved today. A positive 20-year NPV means the investment generates a real return above the discount rate. Higher NPV means a better investment.

Combining solar PV with a heat pump is an excellent strategy. The PV generates free electricity during the day, which the heat pump uses for heating and hot water. This effectively gives the heat pump free-fuel operation during sunny hours, dramatically improving overall payback.

Yes, significantly — it cuts the upfront cost. The £7,500 Boiler Upgrade Scheme grant reduces the net cost of a typical ASHP from about £12,000 to £4,500 (the same £7,500 applies to GSHP, taking £24,000 down to £16,500). From 21 July 2026 to 31 March 2027 an enhanced £9,000 grant is available for eligible off-gas-grid homes on oil or LPG; biomass boilers get £5,000. However the grant only lowers the capital cost — the payback period also depends on the annual running-cost saving. At a SCOP of around 3 and current price-cap rates the running-cost saving versus a 90%-efficient gas boiler can be small or even negative, so a low capital cost does not guarantee a short payback.

A heat pump beats a gas boiler on running cost only when its SCOP is greater than the electricity-to-gas price ratio multiplied by the boiler efficiency. With the Ofgem price cap from 1 July 2026 (electricity 26.11p/kWh, gas 7.33p/kWh) the price ratio is about 3.56, so against a 90%-efficient boiler a heat pump needs a SCOP above roughly 3.2 just to break even on fuel. At a SCOP of 3.0 the saving is slightly negative — this is the UK "spark gap", not a calculator error. A higher achieved SCOP (4.0+) or a heat-pump-friendly electricity tariff with a lower unit rate turns the saving positive and shortens payback. Use the advanced ASHP SCOP, GSHP SCOP and boiler efficiency inputs to model your own quote.

Higher electricity prices improve Solar PV and battery payback (more value from self-generated or stored electricity) but worsen heat pump payback (electric heat becomes dearer relative to gas). Time-of-use tariffs with cheap off-peak rates significantly improve battery storage economics. The defaults use the Ofgem price cap unit rates for 1 July to 30 September 2026 (electricity 26.11p/kWh, gas 7.33p/kWh, Direct Debit incl. VAT); update them to your own tariff for an accurate result.