How to Size a Home Battery in South Africa (2026): The Evening Peak Method, With Prices
Your highest grid draw is not at noon. It is after sunset, when the panels have stopped and everyone is home. That evening block is what you are paying peak rates for, and sizing the battery to cover it is usually the single biggest saving available to a South African household.
Why the evening is where the money goes
A typical household load profile has two peaks: a small one in the morning and a large one from roughly 17:00 to 22:00. Cooking, hot water, lighting, laundry, television. On a normal day the array has stopped producing by the start of that window.
Without storage, every one of those kilowatt-hours comes from the grid at full retail. A solar array alone reduces your daytime import and does very little for the expensive part of the day. That is why a solar-only system so often underdelivers against the brochure.
How to size a battery properly
Three steps, using your own bill rather than a rule of thumb.
Step 1: Find your daily consumption
Take the kWh figure off your statement and divide by 30. A home billed 900kWh a month uses about 30kWh a day.
Step 2: Estimate the share that falls after dark
For most households this is 35% to 50%. If you cook electrically and have electric hot water, assume the upper end. Thirty kWh a day at 40% is 12kWh in the evening block.
Step 3: Add margin for depth of discharge and winter
Modern LFP batteries are usually rated on usable capacity, but you still want headroom so the battery is not scraped to empty every night. Cycling a battery shallower extends its life. Add roughly 20%, which takes 12kWh to about 14kWh to 15kWh of storage.
The short version: daily consumption, times your evening share, plus 20%. Most family homes land between 10kWh and 16kWh.
Home battery prices in South Africa, 2026
Live prices from our shop, all including VAT. These are battery modules only. The inverter, and the gateway where one is required, are separate.
Sigenergy SigenStor
| Battery | Capacity | Price incl. VAT |
|---|---|---|
| SigenStor Battery 6.02kWh | 6.02kWh | R29 480 |
| SigenStor Battery 9.04kWh | 9.04kWh | R41 260 |
SigenStor modules stack, so a 9.04kWh unit today can become 18kWh later without replacing the inverter. Most single-phase homes will also need the Sigen Gateway Home SP 12kW at R7 690 to provide whole-home backup switching.
Sunsynk
| Battery | Capacity | Price incl. VAT |
|---|---|---|
| Sunsynk G 5.12kWh LFP | 5.12kWh | R19 200 |
| Sunsynk 5.12kWh LFP WM IP65 | 5.12kWh | R21 560 |
| Sunsynk 10.24kWh LFP | 10.24kWh | R43 450 |
| Sunsynk 15.97kWh LFP WM | 15.97kWh | R69 190 |
Cost per usable kilowatt-hour
The honest way to compare batteries is rand per usable kWh, not sticker price. On the figures above:
- Sunsynk G 5.12kWh: about R3 750 per kWh
- Sunsynk 10.24kWh: about R4 240 per kWh
- Sunsynk 15.97kWh: about R4 330 per kWh
- SigenStor 6.02kWh: about R4 900 per kWh
- SigenStor 9.04kWh: about R4 560 per kWh
Cheapest per kWh is not automatically the right buy. Cycle life, warranty terms, expandability and how well the battery talks to your inverter all move the real cost over ten years. A battery that cannot be expanded is a ceiling you pay for twice.
Three battery mistakes worth avoiding
- Sizing on outage duration instead of daily consumption. Load-shedding is intermittent. Your evening peak is every single day. Size for the daily cycle and the outage cover follows.
- Buying a battery that cannot grow. Household consumption rises, especially if an electric vehicle arrives. Confirm the expansion path before you buy.
- Ignoring the gateway. Whole-home backup usually needs a changeover device. Budget for it rather than discovering it at quotation stage.
Frequently asked questions
How much does a Sigenergy battery cost in South Africa?
The SigenStor 6.02kWh is R29 480 including VAT and the 9.04kWh is R41 260. Both stack, so capacity can be added later. A single-phase home will usually also need the Sigen Gateway Home SP 12kW at R7 690.
What size battery do I need for a normal home?
Most family homes need 10kWh to 16kWh of usable storage. Work it out as daily consumption, times the share you use after dark, plus about 20% margin.
Is a bigger battery always better?
No. A battery that never fully cycles is capital doing nothing. If your array cannot refill it on a winter day, the extra capacity is dead weight. Size the battery and the array together.
How long do home batteries last?
LFP batteries are typically warranted for a defined number of cycles or years, whichever comes first. Check the specific warranty on the product page and confirm whether it is measured in cycles, years or throughput, because those are very different promises.
Next step
Browse all batteries, or use the system designer to size storage against your consumption. If you have not settled on a system size yet, start with the sizing guide.
