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Home energy use calculator

Most household energy goes on heating. Everything else is a rounding error by comparison in a cold climate.

kWh
kWh
kWh
per kWh
per kWh
g/kWh
g/kWh
Annual energy cost
1806.00
= Exact Home energy audit
Per month
150.50
Total energy
17 700 kWh
Carbon dioxide
3420
Energy per square metre
160.9 kWh/m2 Typical older housing
Heating as a share of energy
67.8 %
Heating and hot water cost
1050.00
Electricity cost
756.00
Show the working
  1. Annual heating energy = 12 000
  2. Annual hot water energy = 3000
  3. Annual other electricity = 2700
  4. Gas price = 0.07
  5. Electricity price = 0.28
  6. Gas carbon intensity = 183
  7. Grid carbon intensity = 250
  8. Floor area = 110
  9. thermal_kwh = 12 000 + 3000 = 15 000
  10. Total energy = 15 000 + 2700 = 17 700
  11. Heating and hot water cost = 15 000 * 0.07 = 1050
  12. Electricity cost = 2700 * 0.28 = 756
  13. Annual energy cost = 1050 + 756 = 1806
  14. Carbon dioxide = (15 000 * 183 + 2700 * 250) / 1000 = 3420
  15. Energy per square metre = 110 > 0 ? 17 700 / 110 : 0 = 160.909
  16. Heating as a share of energy = 17 700 > 0 ? 12 000/17 700*100 : 0 = 67.7966
  17. Per month = 1806 / 12 = 150.5

Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.

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    The formula

    • cost = energy x price for each fuel
    • carbon = energy x carbon intensity

    Energy per square metre is the standard efficiency measure. A Passivhaus targets 15 kWh/m2 for heating alone.

    Grid carbon intensity varies by country and by hour. A UK annual average is around 200 g/kWh and falling; some grids are five times that.

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