Solar System Sizing for Nigerian Homes. A Practical Walkthrough
What it actually takes to figure out the right solar system size for your home. Without overbuying or under-sizing yourself into nightly disappointment.
The most common solar installation mistake in Nigeria isn't picking the wrong panels. It's picking the wrong system size. Either too small to actually run what you need, or too large because someone wanted to upsell you. This guide walks through how to size a solar system for a typical Nigerian home, step by step, so you understand what you're paying for and can spot bad advice.
We'll keep the maths simple. By the end, you should be able to estimate your system size within a reasonable margin, and ask the right questions of whichever installer you talk to.
The fundamental question
A solar system has four components:
- Solar panels. Generate DC power from sunlight
- Charge controller. Regulates how that power goes into the battery
- Battery bank. Stores energy for use when the sun isn't shining
- Inverter. Converts DC battery power into AC power for your appliances
To size the system, you need to answer four questions, in order:
- How much energy do you use per day? (kWh)
- How much of that do you want solar to cover?
- How much storage do you need for nights and cloudy days?
- How many panels and what inverter capacity supports the above?
Let's walk through each.
Step 1: Calculate your daily energy use
List every electrical appliance you want the solar system to power. For each, you need two numbers:
- Power rating in watts (W). Usually on a label on the appliance
- Daily use in hours
Multiply them to get watt-hours (Wh) per day. Add them all up. Divide by 1000 to get kilowatt-hours (kWh).
A realistic example for a small home using solar for "essential loads":
| Appliance | Watts | Hours/day | Wh/day |
|---|---|---|---|
| LED bulbs × 6 | 60 (10W each) | 6 | 360 |
| Fridge | 150 | 24 (cycles) | 1,800 |
| Standing fan × 2 | 80 (40W each) | 8 | 640 |
| TV | 120 | 4 | 480 |
| Phones / laptops charging | 50 | 6 | 300 |
| Water pump | 750 | 0.5 | 375 |
| Total | 3,955 Wh = ~4 kWh |
Notice we did NOT include the air conditioner. That's deliberate. We'll come back to it.
Step 2: Decide what you want solar to cover
Most Nigerian homes don't try to run everything off solar. Some loads are too heavy (AC units, water heaters, electric cookers) and trying to cover them blows up the cost.
Realistic options:
- Essentials only: lights, fans, fridge, TV, phone/laptop charging. Typically 3-6 kWh/day.
- Essentials + light cooling: add a small inverter AC running 4-6 hours. Typically 8-12 kWh/day.
- Full home off solar: every load. Typically 20-40 kWh/day. Expensive.
For this walkthrough, we'll size for essentials only , 4 kWh/day.
Step 3: Calculate battery storage needed
You need enough battery storage to run your essential loads at night plus a buffer for cloudy days.
Battery capacity is measured in amp-hours (Ah) at a specific voltage (usually 12V or 24V). To convert kWh to Ah:
Ah = (kWh × 1000) / Voltage
For a 24V system covering 4 kWh per night with a 50% depth of discharge (recommended for lead-acid; lithium can go deeper):
Ah needed = (4 × 1000) / 24 / 0.5 = 333 Ah at 24V
That's roughly two 200Ah 12V batteries in series.
For lithium-ion (which can use 80% depth of discharge):
Ah needed = (4 × 1000) / 24 / 0.8 = 208 Ah at 24V
Lithium costs more upfront but lasts 3-5x longer and is lighter.
Step 4: Calculate panel capacity
You need enough panel capacity to recharge the batteries during sunlight hours.
Jos gets roughly 5 hours of peak sun equivalent per day on average. To deliver 4 kWh of useful energy after system losses (typically 20-25%), you need panel capacity of:
Panel Wp needed = (4 × 1000 × 1.25) / 5 = 1,000 Wp
That's 4 × 250W panels, or 5 × 200W panels, or similar combinations. With a bit of headroom for cloudy days, we'd recommend 1,200-1,500Wp for this load profile.
Step 5: Inverter sizing
The inverter must handle peak power. The maximum wattage you might draw at one time.
Adding the peak draws (not all running simultaneously, but worst case):
- Fridge starts: 600W (motor starting current is higher than running)
- Fans running: 80W
- Lights: 60W
- TV: 120W
- Water pump running: 750W
Peak realistic: roughly 1,500-2,000W.
A 3kW (3,000W) pure sine wave inverter handles this comfortably with headroom for surge loads.
Putting it all together: example system
For a small Nigerian home covering essentials:
- 5 × 300Wp solar panels = 1,500Wp
- 3kW pure sine wave hybrid inverter (24V)
- 2 × 200Ah 24V lithium batteries (or 4 × 200Ah lead-acid in 24V configuration)
- MPPT charge controller (often integrated into modern hybrid inverters)
- Mounting, wiring, breakers, monitoring
Why people get this wrong
Mistake 1: Sizing for grid voltage instead of actual load. "I have a 20A breaker so I need 5kW of solar". Wrong. You need solar for what you actually use, not what the grid could theoretically supply.
Mistake 2: Ignoring AC starting currents. Air conditioners draw 3-5x their running wattage briefly when they start. A 1kW AC needs an inverter capable of 3-5kW surge. Many installers undersize the inverter and the system trips.
Mistake 3: Skimping on batteries. The temptation is to buy fewer batteries to reduce cost. Result: every cloudy day, the system runs out before sunrise. You're worse off than before because now you've spent money and still have no power at night.
Mistake 4: Over-buying. The opposite mistake. Installers love to upsell. A 10kW system for a household using 3kWh per day is a waste.
Mistake 5: Cheap batteries. Most premature solar system failures in Nigeria are battery failures. Cheap lead-acid batteries from unknown brands fail within 12-18 months. Reputable brands last 5-7 years. The price difference repays itself many times over.
What to ask an installer
- What's my actual daily kWh usage? If they can't answer, they didn't size your system from real data.
- What inverter brand and model, and what surge rating? Vague answers like "3kW Chinese inverter" are a red flag.
- What battery technology and brand? Lead-acid? Lithium? Which manufacturer? What warranty?
- What's the expected daily generation in Wh, and how does that compare to my usage? You should see at least 20% surplus on the generation side after system losses.
- Can I see one of your existing installations? A serious installer has references.
Final note
Solar in Nigeria is a real solution to a real problem. But it works best when sized properly. Fiitech designs systems based on actual load profiling, not assumptions. If you're planning an installation, do the maths above yourself first. You'll have a sharper conversation with whoever installs your system.
