Convert kWh to GJ
| kWh | GJ |
|---|---|
| 0.5 | 0.0018 |
| 1 | 0.0036 |
| 1.5 | 0.0054 |
| 2 | 0.0072 |
| 3 | 0.0108 |
| 5 | 0.018 |
| 10 | 0.036 |
| 20 | 0.072 |
| 50 | 0.18 |
| 100 | 0.36 |
Each row uses the same factor as the converter above: 1 kWh = 0.0036 GJ.
One kilowatt-hour is 0.0036 GJ, and the number worth carrying in your head is the scaled version: 1,000 kWh = 3.6 GJ. This is the conversion between the unit almost everyone is billed in and the unit several reporting regimes insist on. Your electricity meter counts kilowatt-hours. Australia’s national greenhouse and energy reporting scheme wants gigajoules; so does GRI’s energy disclosure. The gap between the two is a single multiplication — and in one jurisdiction the multiplier is written into law.
To convert kilowatt-hours to gigajoules, multiply by 0.0036. So 1,000 kWh = 3.6 GJ. To go the other way, multiply by 277.778 — one gigajoule is 277.78 kWh. The factor is exact: a kilowatt-hour is 3.6 million joules and a gigajoule is a billion, so the ratio is 0.0036 with nothing rounded away.
GJ = kWh × 0.0036. Reverse: kWh = GJ × 277.778 (or ÷ 0.0036). The 0.0036 is not measured. A kilowatt-hour is 1,000 watts sustained for 3,600 seconds, which is 3.6 × 10⁶ joules; a gigajoule is 10⁹ joules. Both the watt and the second are SI-defined, so the conversion is definitional and carries no uncertainty at all.
| kWh | × 0.0036 | GJ |
|---|---|---|
| 1 kWh | × 0.0036 | 0.0036 GJ |
| 277.78 kWh | × 0.0036 | 1 GJ |
| 1,000 kWh | × 0.0036 | 3.6 GJ |
| 100,000 kWh | × 0.0036 | 360 GJ |
| 140,000 kWh | × 0.0036 | 504 GJ |
| 1,000,000 kWh | × 0.0036 | 3,600 GJ |
How to convert kWh to GJ
Multiply by 0.0036. An office consuming 250,000 kWh of electricity in a year is consuming 900 GJ; a manufacturing site on 4.2 million kWh is on 15,120 GJ. The arithmetic is easiest if you go via the thousand: every 1,000 kWh is 3.6 GJ, so 250 thousand kilowatt-hours is 250 × 3.6.
The risk with this pair is magnitude, not direction. A gigajoule is a large unit and a kilowatt-hour is a small one — there are roughly 278 kWh in a gigajoule — so the two numbers are never close enough to be confused for one another. If a conversion leaves you with a GJ figure of the same order as the kWh figure you started with, the factor has been applied at the wrong power of ten. The sanity check: the figure in gigajoules should always be far smaller, by a factor of nearly three hundred.
GJ to kWh
Multiply by 277.778, or divide by 0.0036. So 500 GJ is 138,889 kWh and 12 GJ is 3,333 kWh. This is the direction you need when a figure arrives in a joule-denominated report and has to be reconciled against a meter reading or an invoice.
Worth noting that the two directions are not symmetrical in their precision. Forward, the factor terminates: 0.0036 exactly. Backward, it recurs — 1 ÷ 0.0036 is 277.777… repeating, so 277.778 is already a rounding. It never matters at reporting scale, but it is the reason a figure round-tripped through both directions can come back a fraction off the number you started with.
0.0036 is a reporting coefficient, not just arithmetic
Most unit conversions are a matter of physics and nothing else. This one is also a matter of law. Under Australia’s National Greenhouse and Energy Reporting scheme, electricity has to be converted into gigajoules before it can be reported, and the multiplier used to do it is set out in the NGER Measurement Determination as an energy content factor. For electricity measured in kilowatt-hours, that factor is 0.0036 — the same number this page converts with, written into a statutory instrument rather than derived at the point of use.
That is a meaningful difference. It means an Australian reporting entity does not choose this conversion or defend it in a methodology note; it applies a prescribed coefficient, and an auditor checks that it applied the prescribed one. The scheme underpins the Safeguard Mechanism, which sets emissions baselines for Australia’s largest facilities, so the conversion sits upstream of a compliance obligation with real financial consequences.
The regulator’s own worked example
The CER’s Reporting energy production and consumption guideline (August 2025) works the conversion directly. For a facility generating electricity on site, reportable energy produced is the quantity of electricity in kilowatt-hours multiplied by the energy content factor for electricity:
| Quantity | Calculation | Reportable energy |
|---|---|---|
| 140,000 kWh generated | 140,000 × 0.0036 | 504 GJ |
| 100,000 kWh generated | 100,000 × 0.0036 | 360 GJ |
| 1,000,000 kWh generated | 1,000,000 × 0.0036 | 3,600 GJ |
One boundary worth keeping straight: NGER thresholds are expressed in terajoules — 200 TJ of energy consumption or production at corporate group level, 100 TJ at facility level — while the energy figures themselves are reported in gigajoules. A site that has converted its electricity to GJ still has one more prefix step to take before it can test itself against a threshold, and that step is GJ to TJ.
Why some frameworks want joules and others want watt-hours
There is no single reporting unit for energy, and the split is not between big numbers and small ones. It is between two unit systems that never merged. Electricity settled on the watt-hour because that is how generation and metering developed; the rest of physics settled on the joule. Reporting frameworks then picked sides, and a multinational can easily owe the same electricity figure to two regimes that want it in different systems.
| Framework | Required unit | System |
|---|---|---|
| NGER (Australia) | GJ | Joule |
| GRI 302-1 | Joules or multiples | Joule |
| ESRS E1-5 (EU) | MWh | Watt-hour |
| UK SECR | kWh | Watt-hour |
GRI’s energy disclosure asks for total energy consumption in joules or multiples, which in practice means gigajoules for almost every reporting organisation. The EU’s climate standard requires energy consumption in megawatt-hours. The UK’s regime requires underlying global energy use in kilowatt-hours, split by electricity, gas and transport fuel. A group reporting under more than one of these is not converting for convenience — it is converting because two mandates disagree.
The choice of prefix within the watt-hour system is a separate question with its own answer, covered on kWh to MWh. This page is about the switch between systems.
ISO 50001 is often described as requiring gigajoules. It does not. The standard requires an energy review that normalises consumption onto a consistent basis so that performance can be tracked over time; it does not prescribe which unit that basis uses. GJ is a frequent choice because it consolidates electricity, gas and fuel cleanly, but a kWh-based energy review is equally conformant.
kWh to GJ conversion table
Both directions, at the magnitudes that actually turn up on bills and in reports.
| kWh | GJ | GJ | kWh |
|---|---|---|---|
| 1 | 0.0036 | 1 | 277.8 |
| 10 | 0.036 | 5 | 1,389 |
| 100 | 0.36 | 10 | 2,778 |
| 500 | 1.8 | 50 | 13,889 |
| 1,000 | 3.6 | 100 | 27,778 |
| 5,000 | 18 | 500 | 138,889 |
| 10,000 | 36 | 1,000 | 277,778 |
| 100,000 | 360 | 5,000 | 1,388,889 |
| 1,000,000 | 3,600 | 10,000 | 2,777,778 |
The emission factor moves the opposite way to the energy
This is where the conversion most often goes wrong, and the error is unusually large. Converting a quantity of energy from kWh to GJ, you multiply by 0.0036 and the number shrinks. Converting an emission factor from per-kWh to per-GJ, you multiply by 277.778 and the number grows — because each gigajoule now covers nearly three hundred times as much electricity as each kilowatt-hour did.
Take the current UK grid factor as published by DEFRA: 0.13096 kg [GreenCalculus grid.gbr.electricity.location_based · DEFRA 2026 'UK electricity'!E25 · v2026.284] CO₂e per kWh. Expressed on a joule basis, the same electricity emission factor is:
| Basis | Factor | Derivation |
|---|---|---|
| Per kWh — as published | 0.13096 | — |
| Per GJ | 36.38 | × 277.778 |
0.0036 and 277.778 are the same relationship inverted. Applying the energy multiplier to a factor, or the factor multiplier to an energy, does not produce a near-miss: it produces an answer wrong by roughly 77,000 times. Unlike a transposed prefix, an error that size is obvious the moment anyone looks at it — but it is easy to introduce in a spreadsheet column that has been copied from the wrong neighbour. The rule, which holds across every unit pair on this site: the number follows the size of the unit underneath it. For the conversions themselves rather than this illustration, see g CO₂/MJ to g CO₂/kWh and t CO₂/TJ to kg CO₂/GJ.
Note also that this page converts energy, not emissions. Multiplying a converted GJ figure by a factor gives an arithmetic result, not a reportable one — a Scope 2 figure depends on the location-based or market-based choice, the residual mix where one applies, and the treatment of any contractual instruments. For that, use the Scope 2 electricity calculator, with the assumptions set out in the Scope 2 electricity methodology. UK filers working to the kWh-denominated regime have the SECR calculator and its methodology.
Where each unit turns up
- kWh — electricity and gas bills almost everywhere, half-hourly settlement data, meter readings, UK SECR disclosures, and the national emission factor datasets that publish electricity per kilowatt-hour.
- GJ — NGER reporting in Australia, GRI energy disclosures, Canadian residential natural gas billing, heat metering across much of continental Europe, and site energy totals in EN and ISO documentation.
- Both together — any multinational reporting into both a joule-denominated and a watt-hour-denominated regime, any energy review consolidating electricity with fuels quoted on a calorific value basis, and any comparison of a metered figure against a primary energy statistic.
For the same bridge at meter scale, kWh to MJ. For the prefix steps within each system, MJ to GJ and kWh to MWh. For heat, which is metered in gigajoules but contracted in megawatt-hours, GJ to MWh. For the North American gas unit, MMBtu to GJ. For intensities rather than energies, CO₂e/kWh to /MWh.
Frequently Asked Questions
Exactly 0.0036. A kilowatt-hour is a thousand watts sustained for 3,600 seconds, which is 3.6 million joules, and a gigajoule is a billion joules — so the ratio is 0.0036 with nothing rounded away. Scaled to a more useful size, 1,000 kWh is 3.6 GJ.
Multiply by 0.0036. So 250,000 kWh × 0.0036 = 900 GJ. The easiest mental route is through the thousand: every 1,000 kWh is 3.6 GJ, so multiply your figure in thousands of kilowatt-hours by 3.6. A quick sanity check — the gigajoule figure should come out roughly 278 times smaller than the kilowatt-hour figure.
277.78 kWh, to two decimal places. The exact value is a recurring decimal — 277.777… — because it is 1 divided by 0.0036. For most purposes 277.8 is close enough, and the rounding never reaches a material size at reporting scale.
Because Australia’s NGER Measurement Determination sets it as the energy content factor for electricity measured in kilowatt-hours, and NGER reports energy in gigajoules. It is the same physical constant this page converts with, but prescribed rather than derived — a reporting entity applies the legislated coefficient rather than justifying its own. The Clean Energy Regulator’s reporting guideline works it directly: 140,000 kWh × 0.0036 = 504 GJ of reportable energy produced.
Joules or multiples, which in practice means gigajoules for most reporting organisations. That puts GRI on the opposite side of the unit divide from the EU’s ESRS climate standard, which requires energy consumption in megawatt-hours, and from UK SECR, which requires kilowatt-hours. An organisation reporting into more than one framework will convert between the two systems rather than choose one.
No — 277.78 is rounded, though the underlying relationship is exact. Forward, the conversion terminates: 1 kWh is 0.0036 GJ precisely. Backward it recurs, because 1 ÷ 0.0036 is 277.777… repeating. The asymmetry is why a figure converted to gigajoules and back again can return a fraction off where it started, which matters for reconciliation tolerances and never for the reported number itself.
Because the unit sits in a different position. When kilowatt-hours are the quantity being counted, moving to the much larger gigajoule makes the number smaller, so you multiply by 0.0036. When kilowatt-hours are the denominator, as in kg CO₂e per kWh, moving to per GJ means each unit now covers nearly 278 times as much electricity, so the number grows. The two multipliers are reciprocals, and applying the wrong one leaves you out by a factor of about 77,000. The number always follows the size of the unit underneath it.
Whichever your framework specifies — this is not a matter of preference. NGER and GRI are joule-denominated; ESRS E1 requires megawatt-hours and UK SECR requires kilowatt-hours. If you report into several, hold the underlying data in the unit your meters produce and convert at the point of disclosure, so there is one source figure and an auditable conversion rather than several parallel versions of the same number.