What size solar system does your home actually need?
Oversizing wastes money; undersizing wastes the whole exercise. The right size follows directly from your monthly bill and what you want the system to do. Here's the plain-language version installers use.
Step 1: pick the job
- Backup only. You want outage insurance — lights, Wi-Fi, TV, fridge, gate. An inverter and battery, no panels. Cheapest entry, and solar-ready for later.
- Hybrid (most homes). Panels + inverter + battery. Sun powers the house by day and charges the battery for evening; the grid becomes your backup instead of your supplier.
- Off-grid. Full independence. Needs a much larger array and battery bank — usually only worth it on plots or where the grid connection itself is unreliable.
Step 2: match your bill to a system
| Monthly bill | Typical fit | What that looks like |
|---|---|---|
| Under R1,500 | Backup, or 3kW hybrid | 3kW inverter, ~5kWh battery, 6 panels |
| R1,500 – R3,000 | 5kW hybrid | 5kW inverter, 5kWh battery, 8–10 panels |
| R3,000 – R5,000 | 5–8kW hybrid | 5–8kW inverter, 10kWh battery, 10–14 panels |
| Over R5,000 | 8kW+ hybrid | 8–12kW inverter, 10–15kWh battery, 14+ panels |
Step 3: mind the three sizing traps
- The geyser. It's 40–50% of most bills. Putting it on a solar geyser, heat pump or a timer shrinks the system you need to buy — often by a full battery's worth of money.
- Startup loads. Pool pumps, borehole pumps and aircons draw a surge when they kick in. The inverter must be sized for the surge, not the average.
- Evening habits. Battery size should cover your actual 6pm–10pm usage. Cooking on gas? Smaller battery. Everything electric? Bigger.
The honest rule of thumb
For a typical three-bedroom East Rand home: a 5kW hybrid with a 5kWh battery covers day-to-day life; add a second battery only if your evenings prove it's needed. Good installers size from your last three months of bills — if a quote arrives without anyone asking for those, keep shopping.
Get sized properly, free
Tell us your bill and suburb — a vetted installer designs the right-size system within 24 hours.
Get my free quote