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What size inverter do I need? A Nigerian home guide

Engr. Tunde Adeyemi, Head of Engineering, Crestgreen Energy

B.Eng Electrical (UNILAG), COREN-registered, NABCEP PV Associate

Updated · 7 min read

The short answer

Add up the watts of everything you run at the same time, multiply by 1.25 for headroom and divide by 800. A typical 3-bedroom flat with a fridge, freezer, fans, TVs and one 1.5HP AC needs a 5kVA inverter. Without the AC, 3.5kVA is enough.

Start with your running load

Your running load is the total wattage of everything switched on at the same moment. It is not the sum of every appliance in the house, because you rarely iron, microwave and pump water at once.

List what runs together at your busiest hour, usually 7–10pm. Use the label on the appliance or our defaults below.

ApplianceTypical watts
LED bulb10W
Ceiling fan70W
43" TV100W
Fridge150W
Chest freezer200W
1HP AC900W
1.5HP AC1,300W

kVA is not the same as kW

Inverters are rated in kVA. Appliances use watts. With a power factor of 0.8, a 5kVA inverter delivers about 4,000W continuously.

We add 25% headroom on top so the inverter isn't running flat out in 40°C heat, which is what kills inverters early.

Allow for motor surge

Fridges, freezers, pumping machines and ACs pull two to three times their running watts for a second when the compressor or motor starts. The inverter's surge rating must cover your running load plus that spike from the largest motor.

This is why a 1HP pumping machine on a 1.5kVA inverter often trips it, even though 750W looks small.

Round up to a standard size

Inverters come in 1, 1.5, 2.5, 3.5, 5, 6, 8, 10, 12, 15, 20 and 30kVA. Always round up, never down.

  • Lights, fans, TV, decoder: 1–1.5kVA
  • Add a fridge: 2.5kVA
  • Add a freezer and pump: 3.5kVA
  • Add a 1.5HP AC: 5kVA
  • Two or three ACs: 8–10kVA

Try it with your own appliances

1. What will you run?

  • LED bulb

    10W

    6

  • Ceiling fan

    70W

    2

  • 43" TV

    100W

    1

  • Fridge

    150W · motor

    1

2. Where and how long?

Your recommended system

Inverter
1.0kVA
450W running, 750W surge
Battery
5.12kWh
2.5kWh used at night
Panels
2 × 550W
1.10kWp
Daily energy
3.4kWh
per day
Ask an engineer

Estimates use Crestgreen's design constants (80% diversity above 5 loads, 3× motor surge, 90% depth of discharge). An engineer confirms every design before install.

Packages mentioned in this guide

  • 3.5kVA

    2–3 bedroom flats

    Home Comfort 3.5kVA

    Freezer, pumping machine and the whole flat

    3.5kVA5.12kWh2.2kWp~10h backup
    ₦3,007,000

    or ₦131,078/month

    Installed price, inc. hardware and installation

  • 5kVA

    3–4 bedroom homes

    Family 5kVA

    One 1.5HP AC by day, the whole house by night

    5kVA5.12kWh3.3kWp~10h backup
    ₦3,631,000

    or ₦158,279/month

    Installed price, inc. hardware and installation

  • 10kVA

    Large duplexes

    Duplex 10kVA

    Run the whole duplex, three ACs included

    10kVA15.36kWh7.7kWp~12h backup
    ₦8,517,000

    or ₦371,264/month

    Installed price, inc. hardware and installation

Products in this guide

Frequently asked questions

Can a 3.5kVA inverter carry a 1.5HP AC?

Only just, and only if almost nothing else is on. The AC's start-up surge plus your other loads will usually trip it. Choose 5kVA if the AC is a must.

Is a bigger inverter always better?

No. An oversized inverter wastes battery through idle consumption (often 50–80W). Size to your load with 25% headroom.

Do I need a 48V inverter?

From 5kVA upwards, yes. Higher battery voltage means lower current, thinner cables and less heat.

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