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Electricity Carbon Footprint Calculator

Enter the electricity used and your grid emission factor.

How it is calculated

CO2 (kg) = kWh × factor, where kWh is the electricity used and factor is the grid emission factor in kg CO2 per kWh. Tons are CO2 ÷ 1000, and the tree figure is CO2 ÷ 21, i.e. a fixed assumption of 21 kg of CO2 absorbed per tree. If you leave the factor empty, the tool uses 0.40 kg/kWh. Zero is accepted and gives zero; a negative kWh or factor returns no result. The factor is a national or regional average that changes by country and year, so look up your own grid's current value.

Worked example

A household uses 350 kWh in a month with a factor of 0.4 kg/kWh. CO2 = 350 × 0.4 = 140.00 kg. In tons that is 140 ÷ 1000 = 0.14 t. Trees to offset: 140 ÷ 21 = 6.67 trees. The tool shows 140.00 kg, 0.14 t and 6.67 trees.

Try this example →

Common mistakes

  • Typing a factor in grams per kWh (for example 400) instead of kilograms (0.4); the result becomes 1000 times too large.
  • Using the factor of another country or an old year; grids change as the generation mix changes.
  • Entering a monthly bill amount in currency instead of the kWh figure printed on the bill.
  • Leaving the factor blank and forgetting that the tool then assumes 0.40 kg/kWh, which may not match your grid.
  • Treating the tree count as a precise offset plan: it is only the CO2 divided by a fixed 21 kg per tree.

About this calculator

Electricity itself doesn't emit CO2 at the point of use, but generating it does — the amount depends entirely on the generation mix feeding the grid, which is why emissions per kilowatt-hour vary widely between a coal-heavy grid and one dominated by hydro, nuclear, or renewables. That relationship is captured in a single number, the grid's emission factor (typically in kg CO2 per kWh), published by grid operators or national energy agencies.

This calculator multiplies electricity used (in kWh) by that emission factor to estimate total CO2 output, then converts it into tons and an equivalent number of trees needed to offset it over their growth. It's used by homeowners and businesses tracking their carbon footprint, and by anyone comparing how their emissions would change if they used a different, greener electricity source or supplier.

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