3kW, 5kW or 8kW backup system: which one fits your home

Start with the essentials, then add

Sit down and list what must work when the power drops. For most families that is the fridge, lights, the Wi-Fi router, the TV and phone charging. Everything else, the kettle, the microwave, the washing machine, is nice to have but can wait an hour.

That list decides the package. Buying bigger than your list means paying for inverter capacity you will never draw, and battery capacity you will rarely empty.

What each package actually runs

Our three standard packages map onto three types of household:

• 3kW inverter with 2.5kWh lithium battery (from R35,000 installed). Lights, TV, Wi-Fi, fridge and charging for a few hours. The right size for a small house or a flat.
• 5kW inverter with 5kWh lithium battery (from R65,000 installed). Everything in the small package, plus a kettle or microwave one at a time, a washing machine, a computer setup and most of the night. The sweet spot for a family home.
• 8kW inverter with 10kWh lithium battery (from R115,000 installed). Whole-house backup short of heavy loads like an electric oven. Geysers need to run on a schedule. The closest thing to off-grid without going full solar.

Be honest about the heavy hitters

Geysers, ovens and underfloor heating are the loads that sink undersized systems. A geyser element alone can draw 3kW, which is why we never promise a 3kW system will run your geyser. If you want geyser coverage, we either size up or wire the geyser onto a switch that only runs when there is enough battery. Both options work, but you need to know the trade-off before you buy, not after the first outage.

The battery matters more than the inverter

The inverter decides how much you can draw at once. The battery decides how long you can draw it. A 5kW inverter with a small battery will go dark quickly under load, which is why our packages pair each inverter with a sensible lithium bank. All of ours use lithium chemistry, which lasts longer, charges faster and takes up a fraction of the space of the old lead-acid banks.

Should you add solar panels?

Panels are an add-on (4x 450W mono panels, fully installed, from R18,000) and they change what the system does. Without panels, you are buying a battery that charges from the grid when the power is on. With panels, the battery charges from the sun during the day, which starts to make sense if your outages run long, or if you simply want to lean less on Eskom and the municipality.

If your only goal is surviving a three hour outage twice a week, panels are optional. If you want to run through a bad week without thinking about it, they are the difference between a backup and a mini power station.