Solar Calculator: What Size System Do I Need?

The biggest mistake people make when going solar is buying the wrong size system — too small and the inverter trips every evening, too large and you pay for batteries you never use. Here is how the sizing works, worked through one real example with the exact same engine that runs our calculator — nothing below is hand-typed.

Step 1: List Your Appliances

Start with every appliance you want to run on solar, how many of each, and how many hours a day you use it. Don't worry about the technical numbers yet — the calculator has an appliance picker with typical wattages built in. Our worked example for this page is a 1.5HP AC (6h), a fridge (8h), two ceiling fans (12h), six LED bulbs (6h) and a 32" TV (5h).

Note on fridges and freezers: the compressor cycles on and off, so even a fridge plugged in 24 hours only draws power for roughly 8 of them. The calculator already uses that duty cycle.

Step 2: Peak kW and kWh Per Day

Two numbers decide everything. Peak load is the wattage of everything that could be on at once — this sizes the inverter. Daily energy (kWh per day) is wattage × hours, summed across appliances — this sizes the battery and the panels.

For the example list above: peak load is 1.65kW, and daily energy is 11kWh. The AC alone is 65% of that daily figure on its own — which is why "can I run AC on solar?" is really a battery question, not an inverter question.

The inverter is sized from the full peak load with 56% headroom (20% growth allowance, never above 80% loading), rounded up to a standard size: 1.65kW × 1.5625 ≈ 2.58kW, which lands on a 3.5kVA inverter for the Standard tier. Banks above two lithium modules move to a 48V/5kVA-or-larger inverter, which is what installers actually fit.

Step 3: Battery Capacity (Lithium Modules)

The calculator quotes lithium (LiFePO4) by default, in standard 5.12kWh modules — the 48V 100Ah packs sold by Felicity, Growatt and Dyness. Battery energy = your daily kWh (plus a 25% allowance) × the share used at night or without grid — 50% for a home with some grid, more with less — divided by 80% usable, then rounded up to whole modules. Budget carries 60% of that, Premium 150%. With everything on, Standard runs about 7h and Premium about 10h.

For the example above at Standard: 11kWh × 1.25 × 0.5, divided by 0.8 usable, rounds up to 2 modules = 10.24kWh nominal. One 5.12kWh module costs ₦1,075,200–₦1,774,100 as of October 2026, which is why battery is usually the largest line on the quote. Lithium lasts 10+ years (3,000–6,000 cycles) against 2–4 years for tubular batteries, so it is what the calculator quotes by default.

Step 4: Panels (600W)

Nigeria gets roughly 4.5 peak sun hours a day. Panel watts needed = daily kWh ÷ (4.5 × 0.75 system efficiency). For 11kWh per day that rounds up to 6 × 600W panels (3.6kWp) at Standard. Premium tier adds 25% extra panel capacity so batteries still recharge on cloudy days.

Tier-1 panels (Jinko, JA Solar, Longi, Trina, Canadian Solar) cost ₦119,700–₦163,800 per 600W panel as of October 2026. Import duty and VAT on panels, inverters and batteries are currently 0%.

What the Calculator Gives You

All of the maths above is built into our free calculator. You pick appliances and quantities; it shows your peak kW and kWh per day, then three sized systems:

• •Budget: Felicity / Sako / SRNE / Yohako inverter, Blue Carbon / ITEL / Cworth lithium, ~4h night backup. Runs essentials; heavy loads only while the sun is up.
• •Standard: Growatt / Luxpower / Must / Solis inverter, Felicity / Growatt / Dyness lithium, ~6h backup. What most Nigerian homes install.
• •Premium: Deye / Victron inverter, Deye / Felicity lithium, ~10h backup, 25% extra panels and app monitoring.

Each tier is an itemised bill of materials: hybrid inverter (brand tier and kVA), lithium modules (count and kWh), 600W panels (count), mounting, cables and protection (rails, DC/AC cable, breakers, surge protector, combiner, earthing, changeover), and installation labour. Every line has a low / typical / high price from Nigerian vendor listings, updated October 2026. The quote carries a short code (for example SB-3.5K-TQ5D46) that rebuilds the exact same quote later, and you can download it as a PDF or image.

Worked Example

Running the example household above (1.65kW peak, 11kWh per day) through the calculator at October 2026 prices gives:

For reference, these are the typical ranges before installation the calculator produces for common Nigerian household sizes:

From Quote to Installed System

When the quote looks right, tap Get this system built. That sends the quote to us and opens WhatsApp. We confirm every line against current vendor stock (the same vendors listed on our brands page), source the equipment, and manage an installer we have already vetted through to commissioning. The calculator estimate is the starting point; the confirmed price comes after we check stock and your site.