SettingsSettings for this calculationUS
Metered consumption over a year.
Use metered data rather than a model where you have it. A twelve-month total avoids the seasonal distortion of extrapolating from one quarter.
Your grid's published factor for the reporting year.
This varies enormously — a heavily hydro or nuclear grid can be below 0.05, a coal-dominated one above 0.8. It also falls year on year in most markets, so an assessment must state which year's factor it used.
Period over which to accumulate.
A longer period flatters whichever option uses less energy, and that is legitimate only if the comparison is honest about what changes across it. Grid carbon intensity is falling in most places, so electricity consumed twenty years from now is unlikely to carry today's factor — holding the factor constant over a long horizon overstates the accumulated total and, with it, the advantage of the efficient option.
Assumed yearly fall in the grid factor.
An assumption, not a fact. Set it to zero to see the result at today's grid and avoid claiming a decarbonisation that has not happened — the difference between the two is often the whole argument in a whole-life carbon assessment.
Annual emissions
9,320 kgCO₂e/year
Arithmetic on the factor you supply. The result is only as good as that factor and the decarbonisation assumption, and the latter is a forecast rather than data.
- Year one, in tonnes
- 9.32 tCO₂e
- Cumulative over 25 years
- 165.5 tCO₂e
- Cumulative at a static grid
- 232.88 tCO₂e
- Difference the decarbonisation assumption makes
- 67.37 tCO₂e
- Final-year factor
- 0.1 kgCO₂e/kWh
They open the calculator with your figures already in it
Operational Carbon from Electricity Calculator: 9,315 kgCO₂e/year — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- Emissions = consumption (kWh) × grid emission factor (kgCO₂e/kWh). Factors are published annually by national authorities and change materially year to year.
- Location-based accounting uses the grid average; market-based accounting uses contracted supply. The two give different answers for the same building.
Inputs used
- Annual electricity use (kWh)
- 45000
- Grid emission factor (kgCO₂e/kWh)
- 0.21
- Projection period (years)
- 25
- Annual grid decarbonisation (%)
- 3
Intermediate steps
- Year one, in tonnes
- 9.32 tCO₂e
- Cumulative over 25 years
- 165.5 tCO₂e
- Cumulative at a static grid
- 232.88 tCO₂e
- Difference the decarbonisation assumption makes
- 67.37 tCO₂e
- Final-year factor
- 0.1 kgCO₂e/kWh
Confidence note: Arithmetic on the factor you supply. The result is only as good as that factor and the decarbonisation assumption, and the latter is a forecast rather than data.
What this calculation does not cover
- Electricity only. Gas, oil, district heat and refrigerant leakage are separate and often larger contributions in an existing building.
- Location-based and market-based accounting give different answers for the same consumption; a report must state which it uses.
- The decarbonisation projection is an assumption about policy and investment over decades. Where the result is used to justify a decision, show it at zero as well — the breakdown gives you both.
Add the equipment this sizes
This result is a specification — 9,320 kgCO₂e/year — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-08-27 · in the site-wide review of 2026-09-06 · v1.0.0
Regulatory standards & verification citations2
- Emissions = consumption (kWh) × grid emission factor (kgCO₂e/kWh). Factors are published annually by national authorities and change materially year to year.
- Location-based accounting uses the grid average; market-based accounting uses contracted supply. The two give different answers for the same building.
Cite this page
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