kVA, kW and kWh: What Your Inverter Rating Means

kVA measures what your inverter can supply at once, kW measures the real work that turns into, and kWh measures how much energy your battery holds. So 2kVA is about 1,600 watts, and a 2.56kWh battery is how long you can keep drawing it.

The three units and what each one measures

So three numbers arrive on three different labels, and none of them is measuring the same thing as the others. That is the whole confusion, and it clears up as soon as you know what each one cannot tell you.

• kVA is on the inverter. It tells you how much you can run at once. It cannot tell you for how long.
• kW is on your appliances. It tells you what they really consume. It cannot tell you what they snatch at the moment of starting.
• kWh is on the battery. It tells you how much energy is stored. It cannot tell you whether the inverter can deliver it fast enough.

Why kVA is not watts: power factor in plain words

First, apparent power is everything the inverter supplies. Then real power is the part that does work in your house. So the gap between them is the power factor, and for most inverters sold here it is 0.8.

Now picture a bottle of soft drink with a head of froth. The bottle is the kVA, the liquid is the kW, and the froth is real but you cannot drink it. So an inverter has to be big enough for the whole bottle while you only ever use the liquid.

Is kVA the same as kW?

No. Because kVA is apparent power and kW is real power, kW is always the smaller of the two unless the power factor is exactly one. Multiply kVA by the power factor to get kW, which for most inverters sold in Nigeria means multiplying by 0.8.

Converting kVA to usable watts

What does 2kVA mean in watts?

About 1,600 watts of real, usable power at a power factor of 0.8. If the label also prints a kW figure, trust that one instead of doing the sum, because it is the manufacturer telling you directly what the unit delivers.

How do you convert kVA to kW?

Multiply the kVA figure by the power factor. So 6kVA at 0.8 gives 4.8kW, which is 4,800 watts. Going the other way, divide kW by the power factor, so a 3kW load needs an inverter of at least 3.75kVA.

How battery kWh relates to inverter kVA

Now this is where the two halves meet. Your inverter sets the ceiling on how much you can draw at any instant, and your battery sets how many hours you can keep drawing it.

So a 6kVA inverter with one small battery runs a lot of appliances for a very short time. And a 2kVA inverter with a large bank runs a few appliances all night. So neither is wrong, but one of them is probably not what you wanted.

However, battery labels give amp hours rather than kWh, which means another unit to convert. Our Ah to kWh calculator does it instantly and shows what you can actually use out of the figure.

Sizing with all three

So work in this order and the three numbers stop fighting each other.

• First, add up what runs at the same time, in watts. That sets your minimum kW, and therefore your kVA.
• Then multiply by the hours you need it for. That gives the kWh your battery has to deliver.
• Add headroom for the surges, because a motor starting is not the same as a motor running.
• Finally, look at the panels, which replace what the battery gave out.

Meanwhile, two worked examples of the first step are written. See what a 2kVA inverter can carry for the smaller house and what a 6kVA inverter can carry for the larger one. For the panels, the working is in how many solar panels a 6kVA inverter needs.

If the labels in front of you still do not agree with each other, send us a photo of them. Message us on WhatsApp on +234 809 988 9885 and we will read them with you.