How to Size a Solar Inverter for a Home in Nigeria

An inverter that is too small trips every time the fridge starts. One that is too big costs your client money they did not need to spend. This guide shows you how to size a solar inverter for a Nigerian home in five steps, with a worked example from a three-bedroom house in Uyo, Akwa Ibom.

Step 1: List every appliance and its running watts

Start with a load list: every appliance the system must power, how many there are, and the running watts of each. Read the watts from the nameplate. If the nameplate only shows amps, multiply amps by the voltage (230 V in Nigeria) to get watts. Our solar load audit checklist walks through this on site.

Step 2: Add up the running load

Multiply each appliance’s watts by its quantity, then add them together. This total is the most the inverter has to supply if everything runs at once.

Be realistic. If your client will never run the pressing iron and the microwave together, you can plan for that, but write the assumption down and tell the client.

Step 3: Check the starting surge

Anything with a motor or compressor, such as a fridge, freezer, pump or air conditioner, draws two to three times its running power for a moment when it starts. Inverter-type fridges and ACs start much more gently.

The peak an inverter must survive is the running load of everything that is on, plus the extra surge of the largest motor as it starts. Check that the inverter’s surge rating on its datasheet covers this peak.

Step 4: Add headroom

Add about 25% on top of the running load. Headroom keeps the inverter cooler, extends its life in Nigerian heat, and leaves room for the extra appliance your client will buy next year.

Step 5: Convert to kVA

Inverters in Nigeria are sold in kVA, while appliances are rated in watts. Divide watts by the power factor, about 0.85 for a typical home, then divide by 1,000 to get kVA. Then choose the next standard size up, such as 1.5, 2.5, 3.5 or 5 kVA.

Worked example: a three-bedroom home in Uyo

• Peak surge: 737 W plus the fridge’s extra 450 W as it starts, which gives 1,187 W.
• With 25% headroom: 737 × 1.25 = 921 W.
• In kVA: 921 ÷ 0.85 ÷ 1,000 = 1.08 kVA.

A 1.5 kVA pure sine wave inverter is the right choice. It covers the 921 W comfortably, and its surge rating should handle the 1,187 W fridge start. Check the datasheet to confirm.

Which battery voltage goes with which inverter?

A common rule in Nigerian installations is 12 V or 24 V for systems up to about 1.5 kVA, 24 V up to about 3.5 kVA, and 48 V for 5 kVA and above. A higher bank voltage means lower current, so cables can be thinner and run cooler. The inverter’s battery current is its watts divided by the bank voltage: 921 W on a 24 V bank draws about 38 A, but only about 19 A on a 48 V bank.

Common inverter sizing mistakes

• Ignoring surge. The system works in the showroom, then trips when the borehole pump starts.
• Mixing up kVA and kW. A 1.5 kVA inverter supplies about 1.2 kW, not 1.5 kW.
• Buying modified sine wave inverters for motors. Fridges, fans and pumps run hotter and noisier on them. Use pure sine wave.
• Sizing the inverter without the battery and panels. The inverter sets the peak power, but the batteries and panels decide how long it lasts. See our panel and battery sizing guide.

Do it faster

Soliqo does these sums for you as you build the load list. It totals the running load, finds the largest surge, adds headroom and shows the inverter size in watts and kVA, along with the battery bank, panels and charge controller. See how it works.