kVA to kWh & kWh to kVA Calculator

kVA vs kWh: power vs energy

kVA is a rate: how much power a generator can deliver at any moment. kWh is a quantity: how much energy is delivered over time. Think of kVA as the size of the tap and kWh as the amount of water that has come out of it.

That's why you can't convert kVA straight to kWh. You also need to know:

• Power factor: to turn kVA into kW (real power). Generators are rated at 0.8.
• Load: generators rarely run flat out, so use the average percentage of the rating actually being drawn.
• Time: how many hours the generator runs.

How to convert kVA to kWh

1. Convert kVA to kW: multiply by the power factor (100 kVA × 0.8 = 80 kW).
2. Apply the average load: 80 kW × 75% = 60 kW.
3. Multiply by the hours: 60 kW × 8 hours = 480 kWh.

So a 100 kVA generator running at 75% load for an 8-hour working day produces about 480 kWh. At full load it produces 80 kWh every hour.

How to calculate kVA from kWh

Working backwards is how you size a generator from an energy figure:

1. Divide the kWh by the hours to get the average kW (240 kWh ÷ 8 h = 30 kW).
2. Divide by the power factor to get kVA (30 ÷ 0.8 = 37.5 kVA).
3. Divide by your target load to build in headroom (37.5 ÷ 0.75 = 50 kVA).

Another example: a site using 1000 kWh over 24 hours needs about 69.4 kVA at 75% load and 0.8 PF, so an 80 kVA generator would suit.

One important caution: a kWh total only gives you the average demand. If your load has peaks, such as motors starting, kitchen equipment, or machinery running at the same time, size the generator for the peak, not the average. Our kW to kVA calculator is the better tool when you know your peak load in kW.

Why load % matters for diesel generators

Diesel generators are happiest working. Running a set at around 50-80% of its rating for most of its life is a good target. Running a diesel engine very lightly loaded for long periods can lead to "wet stacking": unburnt fuel and carbon building up in the exhaust. That's why it's worth not oversizing too far. The 75% default in this calculator builds sensible headroom into the result without leaving the generator underworked.

Estimating fuel from kWh

Once you know the kWh, you can estimate fuel use. As a rough guide, a diesel generator working at a reasonable load uses somewhere around 0.25-0.35 litres of fuel per kWh, so 480 kWh would need roughly 120-170 litres. Fuel efficiency varies by engine and load, so check the fuel consumption figures on each generator's product page for an accurate estimate. Browse our diesel generators to compare.