Home energy carbon calculator

How this calculation works

Your home has two energy streams that carry a carbon cost, and each gets one line of arithmetic:

Electricity (kgCO₂e) = kWh used × your country's grid emission factor

Gas (kgCO₂e) = kWh of gas × 0.18293 kgCO₂e/kWh

The electricity factor depends on geography because it describes how your grid makes power. Singapore generates overwhelmingly from natural gas, which puts its factor near the middle of the global range; coal-heavy grids such as Indonesia's and India's sit well above it, and the UK's sits far below. Gas is different: burning a kilowatt-hour of natural gas releases much the same CO₂ wherever the hob is, so a single combustion factor — the UK DEFRA/DESNZ 2025 value — serves as the international default.

Both inputs come straight off your bills. SP Group states electricity in kWh in the consumption summary, and piped town gas from City Energy is billed in kWh too, usually on the same consolidated bill. For scale: a typical 4-room HDB flat uses roughly 350–450 kWh of electricity a month, going by SP Group's published household averages. One- and two-room flats sit well under that; condos with central air-conditioning and landed homes run higher.

The factors, and where they come from

Choose your region and the matching electricity factor is applied automatically:

| Region | Grid factor (kgCO₂e/kWh) | Source | | --- | --- | --- | | Singapore | 0.4020 (2024, current) · 0.4085 (2023) | EMA, Singapore Energy Statistics | | Malaysia | ~0.61 | Ember (2023) | | Indonesia | ~0.68 | Ember (2023) | | Thailand | ~0.55 | Ember (2023) | | Vietnam | ~0.47 | Ember (2023) | | Philippines | ~0.62 | Ember (2023) | | Japan | ~0.49 | Ember (2023) | | China | ~0.58 | Ember (2023) | | India | ~0.71 | Ember (2023) | | Australia | ~0.56 | Ember (2023) | | United Kingdom | 0.207 | DEFRA/DESNZ 2025 | | United States | 0.3712 | EPA eGRID 2022 | | World average | ~0.48 | Ember (2023) |

Gas uses 0.18293 kgCO₂e/kWh everywhere — the DEFRA/DESNZ 2025 natural-gas combustion factor.

Provenance is part of the product. The Singapore figures are published by the Energy Market Authority under the Singapore Open Data Licence; the UK factors under the Open Government Licence v3.0; the Ember country figures under CC-BY (verified against Ember's 2023 dataset — they are national annual averages, which is why the table says "approximately"); the US figure comes from EPA eGRID, which is public domain. Whatever you calculate, the factor, source, year and licence are printed under the result — nothing to take on faith.

A worked example

Take a 4-room HDB flat that used 400 kWh of electricity and 50 kWh of town gas in a month — squarely inside the typical range:

400 kWh × 0.4020 kgCO₂e/kWh = 160.8 kgCO₂e (electricity)

50 kWh × 0.18293 kgCO₂e/kWh = 9.1 kgCO₂e (gas)

Total: 169.9 kgCO₂e for the month ≈ 2.0 tCO₂e a year at similar usage

Two things jump out. First, gas is a rounding error next to electricity in a Singapore flat — the aircon, water heater and fridge do far more than the hob. Second, geography dominates: the identical 400 kWh drawn from Malaysia's grid would be roughly 244 kgCO₂e (400 × ~0.61), while in the UK it would be 82.8 kgCO₂e (400 × 0.207). A large share of your home footprint is a property of the grid behind the socket, not of your behaviour — which is exactly why the part you do control is worth targeting deliberately.

What actually moves the number

• The aircon setpoint. Cooling is usually the single largest load in a Singapore home. Nudging the setpoint up a degree or two, running a timer instead of leaving it on all night, and keeping filters clean all trim the kWh that dominate your bill. The calculator makes the payoff visible: re-run it with the next bill after a change and the difference is your saving in kgCO₂e.
• The water heater. A storage heater left switched on holds water hot all day whether you shower or not. Switching it on shortly before use — or choosing an instantaneous heater — avoids that standby loss entirely.
• The hob question. Per kilowatt-hour, town gas (0.18293 kgCO₂e) emits less than Singapore grid electricity (0.4020) — but an induction hob puts more of its energy into the pan, and cooking is a small load either way. Don't agonise over it; the aircon matters more.
• Efficiency labels. When a fridge or air-conditioner is due for replacement, the tick rating on the new unit is the one moment you can reset your baseline for the next decade.

What this calculator doesn't cover

• Your full personal footprint. This is household energy only — flights, food, transport and waste are separate exercises with their own factors.
• LPG cylinders. Bottled LPG is sold by the kilogram, not in kWh; the gas field here is for piped gas billed in kWh. Cylinder users should skip it — that consumption needs a different factor and unit.
• Common-area electricity. Lifts, corridor lighting and condo facilities are metered to the building and recovered through service and conservancy charges or maintenance fees — real emissions, but not on your meter.
• Green electricity plans and RECs. This is a location-based calculation using the average grid factor. If you buy a green retail plan or renewable energy certificates, a market-based figure can differ; that adjustment is out of scope here.
• Upstream (well-to-tank) emissions. The factors cover generation and combustion, not the fuel supply chains behind them.

Where this fits in your reporting

Households don't file sustainability reports, but the same arithmetic feeds Scope 3 for any organization with staff working from home: category 7 of the GHG Protocol covers employee commuting and, increasingly, home-office energy use. Some employers — companies, universities, and public agencies alike — are beginning to ask staff for exactly the number this page produces, so a figure with a named factor, source and licence beats a guess. For a Singapore reader specifically, this is one worked example among many the calculator supports; run the same fields for another country and the method is identical.

If you own or help run an organization, the same arithmetic scales straight up: the business electricity calculator applies the same country factors to an office or site bill.

When you'd rather not type numbers in, upload the bill itself — a photo or PDF of an SP Group bill works. The free tier takes 3 documents a day anonymously (10 a day with an email address), files are deleted automatically after 30 days, and there is no signup.

Sources

• Energy Market Authority, Singapore Energy Statistics — grid emission factor tables (Singapore Open Data Licence): ema.gov.sg/resources/singapore-energy-statistics
• UK Government (DEFRA/DESNZ), Greenhouse gas reporting: conversion factors (Open Government Licence v3.0): gov.uk/government/collections/government-conversion-factors-for-company-reporting
• Ember, Yearly Electricity Data — country grid intensities (CC-BY): ember-energy.org/data/yearly-electricity-data
• US EPA, eGRID — United States grid emission factors (public domain): epa.gov/egrid
• GHG Protocol — scope definitions and Scope 2 guidance: ghgprotocol.org