How to Size a Solar System for Your Home in Nigeria

Most people overspend on solar because the system was sized by guesswork. A system that is too small leaves you on the generator. One that is too big wastes money. Sizing correctly takes four steps and a list of what you use.

Step 1: List your appliances and hours

Write down every appliance you want the system to run, its power in watts (printed on the label), and how many hours a day it runs. Multiply watts by hours to get watt-hours (Wh) per day.

Appliance	Watts	Hours/day	Wh/day
LED bulb x8	80 total	6	480
Ceiling fan x3	180 total	8	1,440
Television	100	6	600
Refrigerator	150	12 (compressor cycling)	1,800

Add up the last column. In this example that is 4,320 Wh, or about 4.3 kWh per day.

Step 2: Work out the inverter size

The inverter must handle everything that could run at the same time. Add up the watts of the appliances that may be on together, divide by 0.8 to allow for power factor, then add about 25% headroom. Appliances with motors, such as pumps, freezers and air conditioners, draw extra power when they start, so they deserve special attention.

In the example, peak load is around 510 W. That is well within a small inverter. Add an air conditioner or a pump and the number rises quickly, which is why those appliances change the whole design.

Step 3: Size the battery

The battery stores energy for the evening, the night and outages. A simple approach is to decide how much of your daily use happens when the sun is not shining, then divide by the usable depth of discharge. Lithium (LiFePO4) batteries are commonly used to around 80% depth, which means you do not buy capacity you cannot safely use.

If half of your 4.3 kWh happens after sunset, that is about 2.2 kWh, and with 80% usable depth you would look at roughly 2.7 kWh or more of lithium battery.

Step 4: Size the solar panels

Panels need to produce your daily energy plus the energy that charges the battery. Nigeria typically gets around 4 to 6 peak sun hours a day, and real systems deliver about 75% of the panel rating after losses.

Daily energy divided by sun hours divided by 0.75 gives the panel wattage you need. For 4.3 kWh with 5 sun hours, that is about 1.15 kW of panels, which is roughly two to three 550 W panels.

Common sizing mistakes

• Ignoring startup surge from pumps, freezers and air conditioners.
• Counting on the battery for heavy daytime loads instead of letting the panels feed them directly.
• Forgetting future needs such as an extra freezer or an air conditioner next year.
• Skipping the roof check. Shading and roof space limit how many panels fit.

Try it yourself

You can run the same maths automatically with our free solar calculator. It gives a starting estimate, and a site survey turns it into an exact design.