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, and how our calculator turns it into a priced, itemised quote.

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.

Common appliances and their approximate wattage:

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.

Example: 1 × AC (1,200W, 6h) + 1 × fridge (200W, 8h) + 2 × fans (130W, 12h) + 6 × LED bulbs (60W, 6h) + 1 × TV (60W, 5h). Peak load = 1,650W. Daily energy = 7.2 + 1.6 + 1.56 + 0.36 + 0.3 = about 11 kWh per day. Notice that the AC is 65% of the daily energy on its own — that is why "can I run AC on solar?" is really a battery question.

The inverter is sized from the full peak load with 25% headroom, rounded up to a standard size: 1,650W × 1.25 = 2,062W, so a 2.5kVA inverter. Systems with more than two battery modules move to a 5kVA 48V inverter, which is what installers actually fit.

Step 3: Battery Capacity (Lithium Modules)

The calculator quotes lithium (LiFePO4) only, in standard 5.12kWh modules — the 48V 100Ah packs sold by Deye, Felicity, Growatt and Dyness. Backup energy = average running load (about 60% of peak) × the hours of backup you want, divided by 90% usable depth of discharge, then rounded up to whole modules. Budget tier plans for 4 hours of night backup, Standard for 6, Premium for 10.

For the example above at Standard: 1,650W × 0.6 × 6h = 5.94kWh usable, ÷ 0.9 = 6.6kWh nominal, so 2 modules = 10.24kWh. A 5kWh lithium pack costs ₦1,000,000–₦1,350,000 as of September 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 we no longer quote tubular by default.

Step 4: Panels (550W)

Nigeria gets roughly 5.5 peak sun hours a day. Panel watts needed = daily kWh ÷ (5.5 × 0.78 system efficiency). For 11 kWh per day that is about 2,560Wp, which rounds up to 5 × 550W panels (2.75kWp). 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 ₦185–₦300 per Wp as of September 2026 — roughly ₦100,000–₦165,000 per 550W panel. 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 inverter, budget-tier lithium (Blue Carbon, ITEL, Cworth), ~4h night backup. Runs essentials; heavy loads only while the sun is up.
• •Standard: Growatt / Luxpower / 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), 550W 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 September 2026. The quote carries a short code (for example SB-2.5K-JZMP0K) that rebuilds the exact same quote later, and you can download it as a PDF or image.

Worked Example

Running the example household above (1,650W peak, ~11 kWh per day) through the calculator at September 2026 prices gives:

For reference, these are the typical installed ranges 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.