Our sources

Every figure our calculators use, with where it comes from. Data last updated 2026-10-20; next review due 2026-12-31.

Figures marked estimate are our editorial assumptions rather than published figures. Spot something out of date? Email hello@energysums.co.uk. See also our disclaimer.

Ofgem price cap (1 October to 31 December 2026)

FigureValueUnitSourceUpdated
Electricity unit rate26.32p/kWhofgem.gov.uk2026-10-20
Electricity standing charge54.83p/dayofgem.gov.uk2026-10-20
Gas unit rate7.97p/kWhofgem.gov.uk2026-10-20
Gas standing charge29.68p/dayofgem.gov.uk2026-10-20
VATGas includes 5% VAT. No VAT on electricity 1 Oct 2026 to 31 Mar 2027.ofgem.gov.uk2026-10-20

Import tariffs

FigureValueUnitSourceUpdated
Standard variable (price cap average): peak rate26.32p/kWhofgem.gov.uk2026-10-20
Standard variable (price cap average): off-peak rate26.32p/kWhofgem.gov.uk2026-10-20
Standard variable (price cap average): off-peak window0hours/dayofgem.gov.uk2026-10-20
Standard variable (price cap average): standing charge54.83p/dayofgem.gov.uk2026-10-20
Economy 7 (typical, estimate): peak rate (estimate)32.0p/kWhofgem.gov.uk2026-10-20
Economy 7 (typical, estimate): off-peak rate (estimate)15.0p/kWhofgem.gov.uk2026-10-20
Economy 7 (typical, estimate): off-peak window (estimate)7hours/dayofgem.gov.uk2026-10-20
Economy 7 (typical, estimate): standing charge (estimate)54.83p/dayofgem.gov.uk2026-10-20
Octopus Go (EV, 4h off-peak; day rate estimate): peak rate (estimate)26.5p/kWhenergy-review.co.uk2026-10-20
Octopus Go (EV, 4h off-peak; day rate estimate): off-peak rate (estimate)8.21p/kWhenergy-review.co.uk2026-10-20
Octopus Go (EV, 4h off-peak; day rate estimate): off-peak window (estimate)4hours/dayenergy-review.co.uk2026-10-20
Octopus Go (EV, 4h off-peak; day rate estimate): standing charge (estimate)54.83p/dayenergy-review.co.uk2026-10-20
Cosy Octopus (heat pump, blended estimate): peak rate (estimate)40.03p/kWhenergy-review.co.uk2026-10-20
Cosy Octopus (heat pump, blended estimate): off-peak rate (estimate)14.0p/kWhenergy-review.co.uk2026-10-20
Cosy Octopus (heat pump, blended estimate): off-peak window (estimate)8hours/dayenergy-review.co.uk2026-10-20
Cosy Octopus (heat pump, blended estimate): standing charge (estimate)54.83p/dayenergy-review.co.uk2026-10-20

Export (SEG) tariffs

FigureValueUnitSourceUpdated
Statutory-minimum style SEG (e.g. British Gas Export SEG)3.0p/kWhsolarbatterygrants.co.uk2026-10-20
Octopus SEG (fixed)4.1p/kWhoctopus.energy2026-10-20
Outgoing Octopus (variable, Octopus import needed)12.0p/kWhoctopus.energy2026-10-20
EDF Export Exclusive 12m (fixed)18.0p/kWhsolarbatterygrants.co.uk2026-10-20

Solar yield by region

FigureValueUnitSourceUpdated
South West England (estimate)1000kWh per kWp per yearre.jrc.ec.europa.eu2026-10-20
South East & London (estimate)960kWh per kWp per yearre.jrc.ec.europa.eu2026-10-20
East of England (estimate)940kWh per kWp per yearre.jrc.ec.europa.eu2026-10-20
Wales (estimate)920kWh per kWp per yearre.jrc.ec.europa.eu2026-10-20
Midlands (estimate)900kWh per kWp per yearre.jrc.ec.europa.eu2026-10-20
North West England (estimate)860kWh per kWp per yearre.jrc.ec.europa.eu2026-10-20
North East & Yorkshire (estimate)850kWh per kWp per yearre.jrc.ec.europa.eu2026-10-20
Northern Ireland (estimate)830kWh per kWp per yearre.jrc.ec.europa.eu2026-10-20
Scotland (south) (estimate)820kWh per kWp per yearre.jrc.ec.europa.eu2026-10-20
Scotland (north) (estimate)760kWh per kWp per yearre.jrc.ec.europa.eu2026-10-20

Roof orientation factor

FigureValueUnitSourceUpdated
South (estimate)1.0× yieldre.jrc.ec.europa.eu2026-10-20
South-east / South-west (estimate)0.95× yieldre.jrc.ec.europa.eu2026-10-20
East / West (estimate)0.82× yieldre.jrc.ec.europa.eu2026-10-20
North-east / North-west (estimate)0.65× yieldre.jrc.ec.europa.eu2026-10-20

Installation costs

FigureValueUnitSourceUpdated
Solar panels, per kWp (estimate)£1,500Editorial estimate2026-10-20
Solar panels, fixed cost per job (estimate)£1,000Editorial estimate2026-10-20
Battery, per kWh (estimate)£450Editorial estimate2026-10-20
Battery, fixed cost per job (estimate)£1,200Editorial estimate2026-10-20
Air source heat pump, installed (estimate)£12,500Editorial estimate2026-10-20
VAT on solar, batteries and heat pumps0% in Great Britain until 31 Mar 2027gov.uk2026-10-20

Heat pumps

FigureValueUnitSourceUpdated
Default heat pump efficiency (SCOP) (estimate)3.0Editorial estimate2026-10-20
Gas boiler efficiency (estimate)0.88fractionEditorial estimate2026-10-20
Typical gas use (Ofgem medium)9500kWh/yearofgem.gov.uk2026-10-20
Typical electricity use (Ofgem medium)2500kWh/yearofgem.gov.uk2026-10-20

Boiler Upgrade Scheme grants

FigureValueUnitSourceUpdated
Air source heat pump£7,500gov.uk2026-10-20
Ground source heat pump£7,500gov.uk2026-10-20
Air-to-air heat pump£2,500gov.uk2026-10-20
Biomass boiler£5,000gov.uk2026-10-20
Off-gas (oil/LPG) bonus, until March 2027£1,500gov.uk2026-10-20
Available inEngland and Walesgov.uk2026-10-20

Electric vehicles

FigureValueUnitSourceUpdated
Default efficiency (estimate)3.5miles/kWhEditorial estimate2026-10-20
Charging loss (estimate)10%Editorial estimate2026-10-20
Petrol price (estimate)135p/litregov.uk2026-10-20