Home Energy Analysis
Calculate annual electricity and gas costs from your own usage and tariffs; optionally compare gas-boiler and heat-pump energy costs for equal useful heat.
A QUICK WALKTHROUGH
How to use this tool
- Enter your annual electricity/gas kWh, unit rates and daily standing charges.
- Optionally enable heating comparison and enter useful heat, boiler efficiency and COP; calculate.
Calculation
Cₑ = E × rₑ + 365 × sₑ; C𝗀 = G × r𝗀 + 365 × s𝗀; C = Cₑ + C𝗀; C/day = C/365; Cₑ/month = Cₑ/12; Cₑ/day = Cₑ/365; B = H/(η/100); P = H/COP; Δ = B × r𝗀 − P × rₑ. Use one currency throughout. Enter major currency units, not cents or pence: 25 cents/kWh = 0.25 currency unit/kWh. Enter explicit zero for unused gas or a tariff without standing charges. Electricity-only: explicitly enter zero for gas usage, gas unit rate and gas daily standing charge. Electricity monthly cost = annual electricity cost/12; daily cost = annual electricity cost/365. These averages include electricity standing charges.
Scope and assumptions
No tariff or consumption defaults, live data, EPC rating, solar/battery/EV model or carbon estimate. Informational arithmetic only; no equipment sizing, advice or guaranteed savings. A fixed 365-day year and unchanged usage/rates. Enter rates including any applicable tax; no tax is added. Annual cost includes standing charges. Heating comparison uses your separate useful heat demand, a constant efficiency/COP and energy charges only; it excludes standing charges, installation, maintenance and grants. The difference is boiler cost minus heat-pump cost, not whole-home savings. Rounded results do not imply measurement accuracy. For positive heat and both positive rates, equal energy costs occur at COP = electricity rate × efficiency fraction / gas rate. Zero heat gives equal costs for every COP. If both rates are zero, every COP ties. With only one zero rate there is no positive break-even COP. These are entered constant-energy scenarios, not equipment or COP recommendations.
Input limits
Enter finite values: usage/heat 0–10,000,000 kWh; rates and daily charges 0–1,000 currency units; efficiency 1–100%; COP 0.1–20. All enabled fields are required. Each result must have absolute value at most 1,000,000,000,000. Calculations outside the numeric range or losing a positive term through floating-point rounding are rejected. Optional COP comparisons accept 1–20 comma-separated values in 0.1–20. Currency labels cannot contain control characters.
GOOD TO KNOW
Common questions
Are values uploaded?
Values are calculated in this browser tab, without upload or storage.