The single most common mistake we see is guessing at system size — either from a fixed budget ("I have ₦1.5 million, what can I get?") or from what a neighbor bought. Both approaches can leave you under-powered and still reaching for the generator, or paying for capacity you'll never use.
The right way to size a system starts with your actual appliances, not your budget. Here's the process our engineers use — the same logic that powers our free Power Audit calculator.
Step 1: List Every Appliance You Want to Run
Start with everything that needs power during an outage — not just the essentials. Common categories:
- Lighting — LED bulbs, security lights
- Cooling — fans, air conditioners
- Kitchen — refrigerator, freezer, microwave
- Entertainment — TV, decoder, sound system
- Office — laptop, router, phone charging
- Others — washing machine, water pump, iron
For each one, note its wattage (usually printed on the appliance or its manual), how many you have, and how many hours a day you actually run it.
Step 2: Calculate Your Daily Energy Consumption
Multiply wattage × quantity × hours of use for each appliance, then add them all up. This gives you your total daily consumption in watt-hours (Wh). For example:
| Appliance | Watts | Qty | Hours/day | Wh/day |
|---|---|---|---|---|
| LED bulbs | 10W | 6 | 8 | 480 |
| Refrigerator | 150W | 1 | 24 | 3,600 |
| Ceiling fans | 75W | 3 | 10 | 2,250 |
| TV | 50W | 1 | 6 | 300 |
This household would need roughly 6,630Wh (6.6kWh) per day — before adding anything else, like an AC unit or a water pump.
Step 3: Size Your Inverter
Your inverter needs to handle your peak simultaneous load — everything that could realistically be running at once — plus a safety margin for appliances like fridges and pumps that draw extra power when they start up. A common rule of thumb is to add about 25% headroom on top of your peak load in watts, then convert to kVA. A home with a 2,000W peak load, for example, would typically need a system in the 2.5kVA range, which usually means shopping in the 3.5KVA class once you round up to a standard inverter size.
Step 4: Size Your Battery Bank
Your battery needs to store enough energy to cover your daily consumption, accounting for the fact that lithium batteries shouldn't be discharged all the way to zero. A typical depth-of-discharge assumption is 80%, so: battery capacity ≈ daily consumption ÷ 0.8. For the 6.6kWh example above, that works out to roughly an 8–10kWh battery bank.
Step 5: Size Your Solar Panels
Panels need to generate enough energy during daylight hours to cover your daily consumption and recharge your battery. Nigeria typically sees around 5 peak sun hours a day, and real-world systems lose some energy to conversion and wiring inefficiency — a reasonable planning assumption is about 75% system efficiency. Using 400W panels as a reference point:
Panels needed ≈ daily consumption ÷ (5 sun hours × 0.75 efficiency) ÷ 400W
For the 6.6kWh example, that's roughly 6 panels of 400W each.
Common Sizing Mistakes
- Forgetting startup surge. Fridges, pumps, and AC units draw a spike of power when they switch on — undersized inverters trip under this load even if the running wattage looks fine on paper.
- Sizing for today, not for growth. If you're likely to add an AC unit or expand the household in the next few years, it's often cheaper to size slightly larger now than to retrofit later.
- Ignoring depth of discharge. A "10kWh battery" doesn't mean 10kWh of usable power every day if you want it to last years, not months.
- Buying panels without checking roof space. Always confirm your roof or mounting area can actually fit the panel count you need before finalizing a quote.
Skip the Manual Math
All five steps above are exactly what our Power Audit calculator does automatically — pick your appliances, adjust quantities and hours, and it instantly gives you a recommended inverter, battery, and panel count, plus an estimated cost range. It takes about two minutes and gives you a real number to work from instead of a guess.
