Running-cost planner

What could different heating systems cost to run in your home?

Compare your current fuel with direct electric, a ZEB heat battery and an air-source heat pump. This is a transparent planning tool, not a quote or performance guarantee. You control every assumption.

Your property and tariff assumptions

Annual space-heating demand (kWh)Annual hot-water demand (kWh)Gas unit rate (p/kWh)Ofgem average direct-debit rate, 1 Jul–30 Sep 2026; regional and tariff differences apply.Oil price (p/kWh)Enter your own delivered-oil price.LPG price (p/kWh)Enter your own LPG price.Peak electricity rate (p/kWh)Ofgem average direct-debit rate, 1 Jul–30 Sep 2026; time-of-use rates vary.Off-peak electricity rate (p/kWh)Enter the rate from your actual time-of-use tariff.ZEB efficiency assumption (%)Editable planning assumption. Confirm a system-specific seasonal estimate with the installer.Estimated off-peak ZEB charge (%)Not all charging is assumed to occur at the lowest rate.Estimated peak/top-up ZEB charge (%)Solar contribution to heating electricity (kWh)Optional; this is not a solar-generation forecast.Air-source heat-pump SPFSeasonal performance factor, not laboratory COP.

Indicative annual comparison

Your results at a glance

Total useful heat: 14,500 kWh/year.

System	Annual energy	Energy + standing charges	Monthly equivalent
Existing gas Assumes an editable 90% boiler efficiency; gas standing charge included.	16,111 kWh	£1,287	£107
Oil Enter your delivered oil price; model assumes an editable 85% seasonal efficiency.	17,059 kWh	£0	£0
LPG Enter your LPG price; model assumes an editable 85% seasonal efficiency.	17,059 kWh	£0	£0
Direct electric All useful heat is charged at the entered standard electricity rate.	14,500 kWh	£3,995	£333
ZEB heat battery 70% off-peak / 30% peak charging, 40 kWh stated usable-storage context, minus entered solar contribution.	16,111 kWh	£3,050	£254
Air-source heat pump Annual model uses SPF 3.1, not a laboratory COP.	4,633 kWh	£1,418	£118

ZEB tariff sensitivity

At your entered mix, the ZEB blended electricity rate is 17.6p/kWh. A 15% increase in both entered electricity rates would change the ZEB energy element by about £426/year.

What could change these numbers?

Actual heat demand, building fabric, controls, hot-water use, tariff windows, charging behaviour, solar timing, cylinder strategy, installation design and regional rates can all move the result. Standing charges are shown separately; service, maintenance, finance, installation and grants are excluded.

How this calculator works

Useful space heat and hot-water heat are added together. Gas, oil and LPG divide that heat by the entered seasonal boiler efficiency. Direct electric uses one kWh of electricity per kWh of useful heat. ZEB divides useful heat by your stated efficiency, deducts any entered solar contribution and prices the remainder using a weighted mix of off-peak and peak electricity. The air-source heat-pump model divides useful heat by the stated seasonal performance factor. The visible defaults for standard gas, electricity and standing charges follow Ofgem’s published Great Britain Direct Debit averages for 1 July–30 September 2026; they are not a promise of a customer’s actual tariff or regional rate.

For a formal specification or product-specific annual estimate, ask a competent installer to provide an itemised design, heat-loss calculation and tariff rationale.