Most solar advice you get in South Africa is written for Gauteng. The Garden Route is a different problem: our best sun is in December, our worst is in June, and June is exactly when you need the most electricity. If you size your system on a summer day you will be buying a generator by winter.
Why winter decides the size
This is the measured output for one kilowatt of panels on a north-facing roof at 30° near George, from the European Commission’s PVGIS database (SARAH2 satellite data, 14% system losses). These are kWh per kWp per month:
| Month | kWh per kWp |
|---|---|
| January | 140 |
| February | 129 |
| March | 135 |
| April | 118 |
| May | 109 |
| June | 103 |
| July | 111 |
| August | 123 |
| September | 130 |
| October | 139 |
| November | 141 |
| December | 150 |
Annual total: about 1,527 kWh per kWp. December gives you 150. June gives you 103 — a third less, with shorter days and more cloud. So you design for June: about 3.4 kWh per kWp per day, not the 4.8 you see in December.
The four numbers that size the system
- Daily use in kWh. Not the size of your house — the actual number. Read the meter for a week, or add up the appliances you will run.
- Winter yield. Divide daily use by 3.4 to get the panel size in kWp. Then add 10–20% because panels get dirty and hot, and the coast has salt on everything.
- Overnight use in kWh. That is your battery, in usable kWh. Lithium gives you about 90% depth of discharge, lead-acid about 50% — which is why most people replace lead-acid within three years.
- Peak load in kW. Kettle, pump, iron, microwave. The inverter must carry all of them at once, not just the average.
A worked example (illustration, not our system)
Say the house uses 10 kWh a day and 6 kWh of that is after dark:
- 10 ÷ 3.4 = 2.9 kWp minimum, so 3.2–3.5 kWp with margin — six 550 W panels.
- 7–8 kWh of usable battery to cover the evening and a cloudy morning.
- 5 kW inverter if the kettle and pump can overlap.
That is a modest, honest system. What it costs is a separate page — see what off-grid living costs in South Africa.
The three mistakes that cost the most
1. Facing the panels south. Running the same PVGIS model with the array facing south instead of north drops the annual output from 1,527 to 887 kWh per kWp — a 42% loss, forever, for the sake of a roof that looked neater. North, and tilt roughly 30°.
2. Big panels, small battery. Panels are the cheapest part of a system per kWh delivered. Storage is the expensive part. Oversizing panels without matching storage just means throwing away the middle of the day.
3. No load audit. A geyser on a timer, a gas stove and an efficient fridge will do more for your system size than another two panels. Cut the load first, then size the system.
Before you build
Anything connected to the municipal supply in George needs municipal approval and a Certificate of Compliance from a registered electrician — George’s own tariff book sets out how approved solar installations are treated. Do that paperwork first; it is much harder afterwards.
Sources
- PVGIS 5.2 (European Commission Joint Research Centre), SARAH2 database, 33.964°S 22.461°E, 30° tilt, 14% losses — monthly and annual yield.
- George Municipality Tariff Book 2026/2027, as published with NERSA’s decision of 30 June 2026.
- Panel pricing and battery pricing, South Africa, 2026.