Solar sounds like the perfect answer to load-shedding. Free power from the sun, no fuel, no noise. But most people have no idea how many panels they actually need, so they either overspend or buy too little and stay in the dark. This guide gives you a simple way to work it out, without the sales pressure.
Quick answer. Add up the energy your home uses in a day, divide it by the hours of strong sun you get, and add a bit for losses. That gives your panel size. Then add a battery to store power for the hours the sun is not shining. A small home usually needs about 1.5 to 2 kW of panels.
Solar backup is really two parts
People say "solar" as if it is one thing. For beating load-shedding it is two things working together.
The panels make power, but only while the sun is out. The battery stores that power so you can use it in the evening, at night, and during a cut when the sun is weak or gone. Panels without a battery only help you during daylight. If your outages happen at night, the battery is doing the real work. You need to size both.
Step 1, find your daily energy use
Start by working out how much energy your home uses in a day. For each appliance, multiply its watts by the hours you use it. Add them all up. That total, in watt-hours, is your daily use.
For example, three fans at 225 watts running 8 hours use 1,800 watt-hours. A fridge averages around 100 watts across the day, which is about 2,400 watt-hours. Add your lights, TV, and WiFi and a small home often lands near 5,000 watt-hours, or 5 kWh, a day.
Step 2, know your real sun hours
Panels do not make full power all day. What matters is peak sun hours, the number of hours of strong, useful sunlight your area gets. In a sunny country this is often around 5 hours a day, less in winter or on cloudy days.
This one number changes everything. The same panels make more power in a sunny place and less in a cloudy one. Use a realistic figure for your area, and a lower one for winter to be safe. For an accurate figure, look up your location in the US Department of Energy's NREL PVWatts calculator, which models real solar output from decades of weather data.
Step 3, size the panels
Now you can size the panels. Take your daily energy use and divide it by your peak sun hours. Then add roughly 25 to 30 percent for losses, because panels, wires, and the inverter are never perfect.
For the small home above: 5 kWh divided by 5 sun hours is 1 kW. Add losses and you need about 1.25 to 1.5 kW of panels, which is a few panels on the roof.
Step 4, size the battery for the dark hours
The panels handle the daytime. The battery covers the evening and night, when load-shedding hurts most.
Work out how much energy you use after the sun goes down, then size the battery to hold it. Remember that you cannot use all of a battery. With tubular batteries you only use about half, so you need roughly double the capacity. Lithium lets you use most of it. Our battery backup-time calculator helps you check this.
Rough system sizes
| Home | Daily use | Panels | Battery (usable) |
|---|---|---|---|
| Small (lights, fans, TV, fridge) | about 4 to 6 kWh | 1.5 to 2 kW | around 2.5 kWh |
| Medium (adds more appliances) | about 8 to 12 kWh | 3 to 4 kW | around 5 kWh |
| Large (with an air conditioner) | 15 kWh or more | 5 kW or more | 10 kWh or more |
These are starting points, not exact numbers. Your real use decides the size, so measure it first.
Tip. Do not guess your load. List your appliances in our inverter size calculator to see your real wattage, then use that to work out your daily energy and your panel size.
Watch out. The most common solar mistake is buying panels but skimping on the battery. If your outages are at night, a small battery means the panels sit useless after dark. Size the battery for your evening and night use, not just the panels.
Frequently asked questions
Can solar run my home during load-shedding at night?
Only if you have a battery. Panels make power in daylight. To use solar power at night you must store it in a battery during the day.
How many panels is 1 kW?
It depends on the panel. With common 500 watt panels, 1 kW is two panels. With 400 watt panels it is about three. Roof space and panel size decide the exact count.
Do cloudy days ruin solar backup?
They reduce it. On a cloudy day the panels make less, so your battery does more of the work. Sizing with a slightly lower sun-hours figure gives you a safety margin for bad weather.
Is solar cheaper than a generator?
Solar costs more to set up but almost nothing to run, since the sun is free. A generator is cheaper to buy but costs fuel every hour it runs. Over a few years, solar usually wins on running cost.
Size the panels from your real use and sun hours, then add a battery for the dark hours.
Measure your load first, be honest about cloudy days, and you will buy a system that actually beats your outages instead of one that disappoints you.
Solar is not magic, but the math behind it is simple. Know your daily use, know your sun hours, size the panels, then size the battery for the night. Get those four steps right and the sun does the rest.
