Convert kWh to MWh
One megawatt-hour is 1,000 kilowatt-hours, so kWh to MWh is a division by a thousand. It is the simplest conversion on this site, and also the one most likely to cost someone a factor of a thousand in a published emissions figure. Two things make it slippery: a megawatt is not a megawatt-hour, and the same thousand that you divide by here has to be multiplied when the unit turns up in an emission factor. Both are covered below.
To convert kilowatt-hours to megawatt-hours, divide by 1,000. So 5,000 kWh = 5 MWh. To go the other way, multiply by 1,000 — 2.5 MWh is 2,500 kWh. It is an SI prefix step: “mega” is a thousand “kilo”, exactly and by definition.
MWh = kWh ÷ 1,000. Reverse: kWh = MWh × 1,000. Nothing here was measured and nothing can be revised — the prefixes k (10³) and M (10⁶) are defined by the International System of Units, so the conversion is exact. The same step repeats all the way up the ladder: 1,000 MWh is a GWh, 1,000 GWh is a TWh.
| kWh | ÷ 1,000 | MWh |
|---|---|---|
| 1 kWh | ÷ 1,000 | 0.001 MWh |
| 1,000 kWh | ÷ 1,000 | 1 MWh |
| 5,000 kWh | ÷ 1,000 | 5 MWh |
| 250,000 kWh | ÷ 1,000 | 250 MWh |
How to convert kWh to MWh
Move the decimal point three places to the left. A UK household on the regulator’s medium consumption benchmark uses about 2,700 kWh of electricity a year, which is 2.7 MWh. A small office metered at 84,000 kWh is running at 84 MWh.
Because it is a decimal shift rather than a real multiplication, the arithmetic is never the failure mode. The failure mode is doing it in the wrong direction, or on the wrong quantity — and both have a distinctive signature. An emissions figure that is out by exactly 1,000, or exactly 1,000,000, is almost never a modelling error. It is a prefix.
MWh to kWh
Multiply by 1,000, or move the point three places right. This is the direction most people need, because the two units belong to different documents: your meter and your bill are in kWh, while generation data, power-purchase agreements, renewable certificates and grid statistics are all in MWh or larger. Reconciling a bill against a contract means bringing them onto one rung.
The full prefix ladder: Wh to TWh
Every rung is a factor of a thousand, so this one conversion answers all of them.
| Unit | Watt-hours | In kWh | Roughly what it is |
|---|---|---|---|
| Wh — watt-hour | 1 | 0.001 | Charging a phone takes something like 10–20 Wh |
| kWh — kilowatt-hour | 10³ | 1 | The unit on your bill; about an hour of a fan heater |
| MWh — megawatt-hour | 10⁶ | 1,000 | Roughly four months of a UK home’s electricity |
| GWh — gigawatt-hour | 10⁹ | 10⁶ | The scale utility generation and large industrial sites report in |
| TWh — terawatt-hour | 10¹² | 10⁹ | National annual electricity consumption is counted in these |
| PWh — petawatt-hour | 10¹⁵ | 10¹² | Global electricity generation is a few tens of PWh a year |
The ladder is worth internalising as a single object rather than five separate conversions, because in practice you rarely move one rung. Going from a meter reading to a national statistic is a jump of a billion, and that is much easier to get right if you are counting rungs than if you are counting zeros.
MW is not MWh: power versus energy
This is the most expensive confusion in this part of the unit system, and it is not a conversion problem — it is a category difference.
A megawatt (MW) is a rate — how fast energy is being delivered at an instant. A megawatt-hour (MWh) is an amount — how much was delivered in total. The relationship is the one between speed and distance: MW is the speedometer, MWh is the odometer. You cannot convert one into the other without a duration, exactly as you cannot turn a speed into a distance without a time. A 5 MW solar farm does not produce 5 MWh. It produces 5 MWh only during an hour in which it runs at full output, which is not most hours.
The bridge, when you do have a duration, is a multiplication: MWh = MW × hours. Over a full year that is 8,760 hours, but almost nothing runs flat out for all of them, so real output is the nameplate rating multiplied by the hours multiplied by a capacity factor — typically somewhere between a tenth and a half, depending on the technology and the site. That is why a plant’s megawatts and its megawatt-hours are never in a fixed proportion across two different plants.
The confusion is costly rather than academic because both figures appear in the same documents. Grid connection offers, planning applications and power-purchase agreements quote capacity in MW and volume in MWh, often on the same page, and swapping them mis-sizes a procurement by however many hours were involved.
The thousand that goes the other way
Here is the part that catches careful people. Converting kWh to MWh, you divide by a thousand. Converting an emission factor from per kWh to per MWh, you multiply by a thousand. Both are correct, and they look like a contradiction until you see why.
When the kilowatt-hour is the quantity itself, making the unit a thousand times bigger makes the number a thousand times smaller. When the kilowatt-hour sits in the denominator — kg CO₂e per kWh — making that unit a thousand times bigger means each unit now covers a thousand times as much electricity, so the number attached to it grows.
Take 5,000 kWh on the UK grid, currently 0.131 kg CO₂e per kWh [GreenCalculus grid.gbr.electricity.location_based · DEFRA 2026 'UK electricity'!E25 · v2026.203] (DEFRA, location-based). At that factor:
In kWh: 5,000 × 0.131 = 655 kg CO₂e.
In MWh: 5,000 ÷ 1,000 = 5 MWh, and 0.131 × 1,000 = 131 kg CO₂e/MWh, so 5 × 131 = 655 kg CO₂e.
The same answer, because the two thousands cancel. If you divide both — or multiply both — you land a millionfold out, and the tell is that the answer is wrong by exactly 10⁶. The rule: if the kWh is the thing you are counting, divide. If it is underneath, multiply.
The intensity conversion has its own page — see CO₂e/kWh to CO₂e/MWh, and kg CO₂e/kWh to lb/MWh if you are moving between a metric factor and an American one, which adds a pounds conversion on top of the thousand.
Why MWh is the unit of the energy market
The split between the two units is not arbitrary. The kilowatt-hour is the unit of consumption — it is what meters count and what bills are denominated in, because it is the size of a domestic decision. The megawatt-hour is the unit of the market, because it is the size of a wholesale one.
- Certificates are issued per MWh. Renewable energy certificates, guarantees of origin and RECs are minted one per megawatt-hour generated — see energy attribute certificates. A Scope 2 market-based claim is therefore assembled in MWh even when the underlying consumption data arrived in kWh.
- Contracts are struck per MWh. Wholesale power, power-purchase agreements and balancing prices are quoted in currency per MWh, so a £/MWh figure divided by a thousand is the £/kWh a bill would show before network charges and levies.
- Grid factors come in both. UK DEFRA publishes electricity factors per kWh; the US EPA’s eGRID publishes them in pounds per MWh. Two datasets, three unit differences, one very easy mistake.
- Generation statistics climb further. Plant output is reported in GWh and national consumption in TWh, both of which are just this conversion applied again.
If your task is turning a megawatt-hour figure into a market-based Scope 2 position, the unit conversion is the trivial part — the renewable procurement calculator handles the certificate matching and residual-mix treatment that follow. For a location-based figure from metered consumption, use the Scope 2 electricity calculator, and the Scope 2 electricity methodology sets out the assumptions behind both.
Where each rung turns up
- kWh — meters, utility bills, appliance ratings, EV charging sessions, and the electricity emission factors most national datasets publish.
- MWh — wholesale trading, PPAs, renewable certificates, corporate energy contracts, half-hourly settlement data, and site-level reporting for anything larger than a small building.
- GWh — generator output, large industrial sites, data centre estates, and utility annual reports.
- TWh — national energy balances, IEA and Ember datasets, and decarbonisation scenarios.
For the same energy in metric heat units see kWh to MJ (exact, ×3.6). For the American energy units see kWh to BTU and kWh to therms, which also covers the gross-versus-net calorific basis question that applies whenever the energy is fuel rather than electricity. If what you are converting is an intensity rather than an energy, start at CO₂e/kWh to /MWh.
Frequently Asked Questions
Exactly 1,000. A megawatt-hour is a thousand kilowatt-hours, because “mega” is a thousand times “kilo” in the International System of Units. It is a definition rather than a measurement, so the conversion is exact.
Divide by 1,000, or move the decimal point three places left. So 5,000 kWh = 5 MWh, and 2,700 kWh = 2.7 MWh. To reverse it, multiply by 1,000.
A megawatt is a rate of power; a megawatt-hour is an amount of energy. MW is the speedometer and MWh is the odometer — you cannot convert between them without a duration. A 5 MW solar farm produces 5 MWh only in an hour of full output, and its annual figure is the capacity multiplied by 8,760 hours and by a capacity factor that is typically between a tenth and a half.
Because the kilowatt-hour is in a different position. When it is the quantity you are counting, a thousand-times-bigger unit gives a thousand-times-smaller number, so you divide. When it is in the denominator, as in kg CO₂e per kWh, each unit now covers a thousand times as much electricity, so the number grows and you multiply. The check: 5,000 kWh at 0.131 kg/kWh is 655 kg, and 5 MWh at 131 kg/MWh is also 655 kg. The two thousands cancel.
Roughly four months of electricity for a UK household on the regulator’s medium consumption benchmark of about 2,700 kWh a year. On the UK grid factor it carries about 131 kg CO₂e. It is also the unit in which one renewable energy certificate is issued.
Yes. Every rung of the ladder is a factor of a thousand: 1,000 Wh is a kWh, 1,000 kWh is a MWh, 1,000 MWh is a GWh, and 1,000 GWh is a TWh. So a GWh is a million kWh, and a TWh is a billion.
Yes — renewable energy certificates, guarantees of origin and equivalent instruments are minted one per megawatt-hour of generation. That is why a market-based Scope 2 position is assembled in MWh even when the consumption data behind it was metered in kWh, and why this conversion sits between the two.
A UK household on the medium consumption benchmark uses about 2,700 kWh of electricity a year, which is 2.7 MWh. A typical US home uses considerably more, in the region of 10,500 kWh or 10.5 MWh, mostly because of air conditioning and electric heating. Neither figure includes gas.