ZEUS.africa

Solar system sizing calculator

Enter what you run and for how long, or a daily kWh figure if you know it. The calculator sizes the array on your city's worst month, the battery on your overnight energy and depth of discharge, and the inverter on your simultaneous load with headroom.

Updated 16 September 2026

Inputs

Sets solar yield (kWh per kWp per day, Global Solar Atlas).
Appliances W · h/day · night h
OnApplianceQtyWh/dayNight h
LED bulb
Ceiling fan
Standing fan
LED TV 43″
Decoder / router
Laptop
Phone charger
Fridge (inverter type)
Chest freezer
Inverter AC 1 HP
Inverter AC 1.5 HP
Non-inverter AC 1.5 HP
Water pump 1 HP
Microwave
Electric kettle
Washing machine
Iron

Compressor loads (fridge, freezer, AC) are multiplied by a duty cycle of 40–70% for energy; running watts are used for the simultaneous load. Edit watts from your appliance labels.

nights
Nights the battery must carry without recharge. 1 for hybrid with grid/generator; 1.5–2 for off-grid.
Worst month keeps the household covered in the rainy season.
W
ResultsLagos
Daily energy
—
kWh/day from your inputs
PV array
—
kWp, sized on the design month
Panels
—
at the wattage you set
Inverter
—
kVA at pf 0.8, 25% headroom
Battery, nominal
—
kWh after DoD and losses
Battery at bus voltage
—
Ah at 12/24/48 V
Average daily output
—
kWh on an average day
Roof area
—
m² with spacing
Enter your inputs.
Formulas and assumptions
E_daily = Σ qty × W × h × duty ÷ 1000
PV_kWp = E_daily ÷ Yield_design ÷ η_batt η_batt 0.87 LiFePO₄ / 0.80 tubular
Panels = ceil(PV_kWp × 1000 ÷ Panel_W)
E_battery = E_night × nights ÷ DoD ÷ η_inv
Inverter_kVA = P_simultaneous × 1.25 ÷ 0.8 ÷ 1000, rounded up to 1 / 1.5 / 2.5 / 3.5 / 5 / 8 / 10 / 15 / 20
Bus = 12 V ≤ 1.5 kVA · 24 V ≤ 3.5 kVA · 48 V above
Roof ≈ Panels × 3 m²

Yield data: Global Solar Atlas PVOUT per city, average and worst month (table). The inverter is rounded to common Nigerian ratings; check surge against your largest motor on the inverter page.

What this is

An estimate from stated formulas and typical values, for planning and for checking quotations. It is not an engineering design, does not replace a load audit and site survey by a qualified installer, and does not account for shading, roof orientation, cable losses or local standards. ZEUS is not an engineering firm.

Safety

Solar arrays produce lethal DC voltages in daylight and cannot be switched off at the panel. Battery banks can deliver thousands of amps into a short circuit. Installation, wiring, earthing and commissioning must be done by a qualified installer or licensed electrician to the manufacturer's instructions and the Nigerian Electrical Installation Standards (IEC 60364-based). ZEUS explains how systems work so you can specify and check them, not so you can wire them yourself.