Every installer has a number for this, and most of them are guesses. The inverter size does not decide how many panels or batteries you need. Your nights decide the battery, and the battery plus your daytime use decide the panels. Here is the arithmetic, with a table for the sizes Nigerians buy and a calculator for your own house.
The short answer
| Inverter | Panels | Lithium battery | Or tubular batteries | Carries |
|---|---|---|---|---|
| 3.5kVA (24V) | 4–6 (2.5–3.7kWp) | 5kWh | 4 | Fridge, lights, fans, TV; no AC overnight |
| 5kVA (48V) | 6–8 (3.7–5kWp) | 10kWh | 8 | One small AC for part of the night |
| 6kVA (48V) | 6–8 (3.7–5kWp) | 10–15kWh | 8–12 | One AC through the night, fridge and freezer |
| 10kVA (48V) | 14–16 (8.7–9.9kWp) | 15–30kWh | 12–24 | Two ACs, borehole pump, a small office |
| 12kVA (48V) | 18 (11.2–11.2kWp) | 15–30kWh | 12–24 | Three ACs, a duplex or office of 8 to 10 staff |
The ranges are wide on purpose. Two 10kVA homes can need very different systems: one runs two ACs all night, the other is empty all day and runs one. That is why the rest of this guide matters more than the table.
How many batteries: start with your nights
The battery carries everything after sunset. Multiply what runs at night by how many hours you want it to run, then allow for the share of the battery you can safely use.
One AC, a fridge and lights, sunset to morning
- Night load: 0.8kW AC + 0.3kW fridge, lights, fans ≈ 1.1kW
- Hours: 10
- Energy needed: 1.1kW × 10h = 11kWh
- Lithium, used to 90%: 11 ÷ 0.9 = 12.2kWh → a 15kWh pack
- Tubular 12V 200Ah, used to 50%: 1.2kWh each → 11 ÷ 1.2 = 9.2 → 12 batteries (three strings of four on 48V)
About 15kWh of lithium, or a dozen tubular batteries, for one AC through the night.
That is the reason we quote lithium. Twelve tubular batteries fill a room, need topping up with distilled water and are usually replaced within a few years; one 15kWh LiFePO₄ pack sits on the wall for ten years or more. The full comparison is in LiFePO₄ vs tubular and AGM batteries.
How many panels: refill the battery and run the day
In Lagos, each kWp of panels makes about 3.6kWh a day averaged over the year (1,310kWh a year). A 620W panel therefore makes about 2.2kWh a day, falling to about 1.7kWh in harmattan and the heaviest rains, when the sun gives 3.45 peak hours instead of up to 5.35.
The same house, with 8kWh of daytime use
- Refill the battery: 11kWh
- Run the day: 8kWh
- Total from the panels: 19kWh a day
- Average month: 19 ÷ 2.2 = 9 panels
- Harmattan: 19 ÷ 1.7 = 11 panels
9 to 11 panels of 620W. Fewer than that and the generator comes back on dull days.
Panels are the cheapest part of a system per kWh it delivers. If the budget is tight, buy enough panels first and add battery later, not the other way round.
Your own numbers
Work out your own
- Lithium battery
- 15kWh
- or 12 tubular 200Ah batteries
- Panels, average month
- 9 × 620W
- 5.6kWp
- Panels, harmattan
- 11 × 620W
- to stay off the generator in the dullest months
Starting from a monthly diesel and NEPA bill rather than a list of appliances? The solar calculator works backwards from what you spend.
What the inverter size does decide
The kVA rating is how much can run at the same moment. It caps your peak, not your energy. Two things to check on any quote:
Starting surge. An AC compressor or a borehole pump draws several times its running power for a second as it starts. Two of those starting together on a small inverter that is already carrying the fridge is the classic way a 3.5kVA or 5kVA system trips.
Maximum solar input. Every inverter’s datasheet gives the most panel power it can take. That, not the kVA, is the ceiling on how many panels you can add later. Ask to see it before you plan to expand.
Worth being honest about: the table assumes an unshaded roof facing roughly south and panels cleaned every few weeks. Dust can cut output by a third or more within months in Lagos, which looks exactly like having too few panels.
For a worked example with a price on it, our InfraSol Home 10 pairs a 10kVA inverter with 16 panels and 30kWh of lithium.