Technical Resource
Solar Kit Sizing Guide
How to calculate the right battery capacity, panel array and inverter size for a residential off-grid or hybrid solar system — with a load reference table and peak sun hour data for West Africa and Southern Africa.
5-Step Sizing Method
List your loads
Write down every appliance that will run on solar: lights, fans, fridge, TV, phone chargers, AC unit, pump. For each, note the wattage (on the label or spec sheet) and how many hours per day you expect to run it.
Check the nameplate wattage, not the rated wattage. A 1.5HP air-con compressor draws ~1,100W when running but its nameplate says 1.5HP. Always use actual running watts.
Calculate daily load (Wh/day)
Multiply each appliance's wattage by hours of use per day. Add them all together to get your total daily energy requirement in watt-hours (Wh). This is your daily energy budget.
Add a 20% buffer for inefficiencies (inverter, cabling, battery charging losses). If your loads total 3,000Wh, size for 3,600Wh.
Size your battery bank
Your battery must store enough energy to cover consumption when the sun is down. Divide your buffered daily load by the battery's depth of discharge (DoD). LiFePO4 can be discharged to 100% — use the full Ah rating. Lead-acid should be limited to 50% DoD.
LiFePO4 example: 3,600Wh ÷ 48V = 75Ah minimum. Choose the next size up — 100Ah gives margin. For 2 days autonomy, double it.
Size your solar array
Divide your daily energy budget by your peak sun hours (PSH). West Africa and southern Africa typically receive 4.5–6 PSH per day. Divide again by panel efficiency loss factor (~0.85 for temperature, wiring and soiling).
Formula: kWp = (Daily Wh × 1.2) ÷ (PSH × 1,000 × 0.85). For 3,600Wh in Lagos (5 PSH): 3,600 × 1.2 ÷ (5 × 1,000 × 0.85) = 1.02kWp minimum. Round up to 1.2–1.6kWp.
Choose your inverter size
The inverter must handle your peak simultaneous load — all appliances that could run at the same time. Sum the wattages of everything that could be on together. Add 25% headroom for motor inrush (pumps, AC compressors draw 3–7× rated watts at startup).
A 1.5HP AC (1,100W) + fridge (150W) + lights (150W) + fan (120W) = 1,520W. With inrush headroom for AC: size inverter at 3,500VA or larger.
Quick Kit Selection Table
Match your daily energy budget and peak load to the right kit size.
| Kit | Daily energy | Battery | Array | Max peak load |
|---|---|---|---|---|
| 1.5kVA Starter Kit | ≤ 1,800Wh/day | 48V 50Ah / 2.4kWh | 1.6kWp (4 × 400Wp) | ≤ 1,200W simultaneous |
| 3.5kVA Family Kit | 1,800–4,800Wh/day | 48V 100Ah / 4.8kWh | 2.4kWp (6 × 400Wp) | ≤ 2,800W simultaneous |
| 5kVA Home & SME Kit | 4,800–9,600Wh/day | 48V 200Ah / 9.6kWh | 4kWp (10 × 400Wp) | ≤ 4,000W simultaneous |
| 10kVA Commercial Kit | 9,600–20,000Wh/day | 48V 400Ah / 19.2kWh | 8kWp (20 × 400Wp) | ≤ 8,000W simultaneous |
Common Appliance Wattage Reference
| Appliance | Typical watts | Notes |
|---|---|---|
| LED bulb 10W | 10W | Per bulb — multiply by count |
| Ceiling fan | 60W | 40–75W depending on speed |
| Floor fan / standing fan | 45W | — |
| 32" LED TV | 55W | Smart TV ~80W |
| 43" LED TV | 80W | — |
| Laptop | 45W | 30–65W depending on model |
| Desktop computer | 120W | Varies; gaming PC much higher |
| Phone charger | 10W | Fast chargers up to 65W |
| 12V fridge (small) | 45W | Average; compressor cycles |
| 230V fridge (130L) | 80W | Average; 120–200W at start |
| 230V freezer (200L) | 110W | Average running |
| 1HP AC unit | 750W | Running — inrush 4,500W |
| 1.5HP AC unit | 1100W | Running — inrush 6,600W |
| 2HP AC unit | 1500W | Running — inrush 9,000W |
| Water pump (0.5HP) | 375W | Running — inrush 2,250W |
| Water pump (1HP) | 750W | Running — inrush 4,500W |
| Electric iron | 1000W | Do not run on inverter if possible |
| Microwave (800W) | 800W | Short bursts — not continuous |
| Electric kettle | 2000W | High demand — size inverter accordingly |
Peak Sun Hours by Location
Annual average PSH (kWh/m²/day). Actual values vary by season, tilt angle and panel orientation. Source: Global Solar Atlas (ESMAP/World Bank).
| Location | Avg PSH | Notes |
|---|---|---|
| Lagos, Nigeria | 5.2 h/day | Harmattan season slightly higher |
| Abuja, Nigeria | 5.6 h/day | Less humidity, better yield |
| Accra, Ghana | 5.1 h/day | Coastal haze reduces yield slightly |
| Johannesburg, South Africa | 5.8 h/day | High altitude, excellent irradiation |
| Cape Town, South Africa | 5.0 h/day | Winter variation significant |
| Nairobi, Kenya | 5.5 h/day | Consistent throughout year |
| Dar es Salaam, Tanzania | 5.0 h/day | Rainy season impacts yield |
| Kigali, Rwanda | 4.8 h/day | Tropical highland; some cloud cover |
Common Sizing Mistakes
Forgetting inrush current
AC units and pumps draw 4–7× running watts at startup. Size your inverter for the peak inrush, not just the running load.
Using nameplate instead of running watts
1.5HP is a mechanical horsepower rating. The actual electrical input of a 1.5HP AC is ~1,100–1,200W when the compressor runs.
Under-sizing battery for night loads
Solar panels stop producing at sunset. Size the battery for the loads you need after dark — don't assume grid backup will always be available.
Ignoring cable losses
Long cable runs from panels to inverter create voltage drop and power loss. Use 6mm² cable for runs over 10m and factor in a 5–8% cable loss in your sizing.
No buffer for cloudy days
Rainy and harmattan seasons reduce generation by 20–40%. Size for 1.5–2 days of autonomy in battery storage if the site is critical.
Mis-matching inverter and battery voltage
Residential systems over 2kVA almost always use 48V battery banks. Verify your inverter and battery are the same nominal voltage (48V ≠ 24V).
Related Tools & Guides
Battery Capacity Calculator
Enter your loads and backup hours to get recommended battery Ah.
PV Cable Voltage Drop Calculator
Check cable sizing for your string length to ensure acceptable voltage drop.
LiFePO4 Battery Shipping Guide (UN38.3)
Understand DG documentation requirements for exporting batteries from China.
Hybrid Inverter Sourcing Guide
How to evaluate hybrid inverters for off-grid and grid-tied markets.
Need help sizing your project?
Send us your load list and site location. We'll return a recommended kit configuration, BOM and indicative pricing within 24–48 hours.