How much solar power does a home need?

Solar sizing starts with your battery, not your roof

A common assumption is that a bigger house needs a bigger solar array. In practice, solar sizing follows your daily energy use, because the array's job is simple: fully recharge whatever your battery discharged the day before, within a normal day of sunlight. A large house with efficient appliances can need less solar than a small flat running a freezer and an AC unit around the clock.

The formula, in plain terms

Solar array size (kW) = Daily energy use (kWh) ÷ average peak sun hours, plus a loss margin

In most of Nigeria, we plan around 4–5 peak sun hours per day on average across the year — not 12 hours of daylight, but the portion of the day when sunlight is strong enough to produce close to a panel's rated output. We also add roughly 15–20% to the raw number to account for system losses: heat, wiring, inverter conversion and panel soiling.

Worked example

A household using 15 kWh a day:

1. 15 kWh ÷ 4.5 sun hours = 3.33 kW (raw requirement)
2. 3.33 kW × 1.2 (loss margin) = ≈4 kW solar array needed

That household would typically be sized to a 5kW array — the next standard size up — which also gives a small buffer for cloudy days.

Standard home sizes, as a starting reference

Package	Solar array	Typical daily use covered
Essential	3 kW	≈8–10 kWh/day
Home Plus	5 kW	≈14–16 kWh/day
Business Pro	8 kW	≈24–28 kWh/day

These are starting points, not fixed rules — your actual number depends on your appliances and usage pattern, which is why every quote follows a proper load calculation.

Why panel count matters less than panel wattage

Two arrays can both be "5kW" using very different numbers of panels, depending on whether you install 450W or 550W panels. Higher-wattage panels mean fewer panels for the same output — useful on smaller roofs — while efficiency (usually 20–22% for the monocrystalline panels we install) determines how much power you get per square metre. On a tight roof, efficiency and wattage matter more than raw panel count.

Roof space is a real constraint — here's how to check it

As a rough guide, a 550W monocrystalline panel measures roughly 2.3m × 1.1m. A 5kW array using nine of these panels needs approximately 23–25 square metres of usable, mostly shade-free roof space. If your roof is smaller or partially shaded, higher-efficiency or bifacial panels can recover some of that lost capacity — something we check during the site survey rather than guess from a satellite photo.

Shade, orientation and roof angle change the outcome

Two identical arrays can produce meaningfully different daily output depending on:

• Orientation. In Nigeria, a roughly south-facing (or north-facing, depending on exact latitude) unobstructed section performs best; east/west-facing sections still work but produce less at peak times.
• Shading. A single shaded panel in a badly wired string can drag down the output of the whole string, not just itself — this is a wiring and design issue as much as a shading one.
• Roof pitch. A shallower or steeper pitch than optimal reduces output slightly; it's rarely worth re-roofing purely to fix this.

Don't oversize just to "be safe"

More solar than your battery can absorb in a day doesn't help — the excess energy simply isn't used once the battery is full and there's nowhere else for it to go (unless you're feeding back to the grid, which most residential systems in Nigeria aren't set up to do). It's more effective to size the array correctly to your load, and add capacity later if your usage grows, than to overbuild from day one.

FAQs

What if my roof faces a difficult direction?
It's rarely a dealbreaker. Our engineers assess actual output for your roof's specific orientation and shading during the site survey, and adjust panel placement or count accordingly.

Can I add more panels later?
Yes, provided your inverter's solar input rating has headroom — one more reason to check that spec before choosing an inverter. See our inverter guide.

Do cloudy days ruin solar output in Nigeria?
They reduce it, but don't eliminate it — panels still generate on overcast days, just at a lower percentage of rated output. This is part of why we size systems with a loss margin rather than assuming perfect sun every day.

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