What Size Battery Do You Need for Load Shedding?
Load shedding has forced most South African homeowners to seriously consider battery backup. But the options are overwhelming, the marketing is aggressive, and the technical jargon — kWh, DoD, LiFePO4, inverter kVA — makes it hard to know where to start.
Here is a plain-language guide to sizing a battery backup system for your home, based on real-world usage data.
Battery capacity is rated in kWh (kilowatt-hours), but you can only use a portion of that capacity safely. Lithium LiFePO4 batteries can use 85% of their rated capacity. Gel/AGM lead-acid batteries should only use 50%. This is called Depth of Discharge (DoD). Always size on usable capacity, not rated capacity.
Step 1 — Decide What Must Stay On
You don't need to run your whole house during load shedding. The goal is to identify the essentials — what actually disrupts your life when the power goes off — and size the battery for those loads only.
Most households find their essential load comes down to:
| Appliance | Typical draw | Notes |
|---|---|---|
| LED lights (3 rooms) | 30W | Very light load |
| Fridge / freezer | 150W avg | Cycles on/off — not constant |
| TV + decoder | 110W | DSTV decoder alone is ~30W |
| WiFi router | 15W | Always on |
| Phone chargers | 20W | 2 phones charging |
| Laptop | 65W | Working from home essential |
| Alarm system | 20W | Security critical |
| CCTV / NVR | 25W | Security cameras |
That list above totals approximately 435W — less than half a kilowatt running simultaneously. This is a very manageable backup load.
Step 2 — How Long Do You Need to Last?
Load shedding stages determine the duration of outages:
| Stage | Hours per day | Battery sizing target |
|---|---|---|
| Stage 1–2 | 2–4 hours | 2h backup |
| Stage 3–4 | 4–6 hours | 4h backup |
| Stage 5–6 | 6–10 hours | 6–8h backup |
South Africa has been predominantly in Stage 2–4 territory. Sizing for 4–6 hours covers most scenarios without grossly oversizing the battery.
Step 3 — The Battery Size Calculation
The formula: Battery kWh needed = (Load in kW × Hours) ÷ DoD
Example: 435W essential load, 4 hours, LiFePO4 battery (85% DoD):
- Raw energy needed: 0.435 kW × 4h = 1.74 kWh
- Rated capacity required: 1.74 ÷ 0.85 = 2.05 kWh minimum
A single 2.4 kWh or 5.12 kWh LiFePO4 battery comfortably handles this. In practice, most installers recommend a 5 kWh minimum for a sensible system with headroom.
What Can't You Run on Battery?
Three appliances will eat your battery extremely fast and require special planning:
Electric Geyser (3,000W)
A 3kW geyser running for 2 hours uses 6 kWh — more than the entire rest of the house combined during a 4-hour outage. Running your geyser on battery backup is expensive and not recommended unless you have a very large battery bank. Options: solar geyser, heat pump geyser, or gas — all better than battery for water heating.
Air Conditioning (1,000–3,500W)
A 1-ton (3.5kW) inverter AC unit draws around 1,000W running and 3,000–4,000W on startup surge. This requires a minimum 5kVA inverter and will drain a 10 kWh battery in 4–5 hours running alone. It's possible but expensive. A smaller 9,000 BTU unit is more manageable.
Kettle (2,200W) and Microwave (1,200W)
These are short-duration high-draw appliances. A kettle uses about 0.18 kWh per boil — not terrible, but the 2,200W surge requires at minimum a 3kVA inverter. Many people switch to a gas stove and gas kettle for load shedding and never look back.
Battery Chemistry — Lithium vs Gel
| LiFePO4 Lithium | Gel / AGM Lead-acid | |
|---|---|---|
| Usable capacity (DoD) | 85% | 50% |
| Cycle life | 3,000–6,000 cycles | 300–500 cycles |
| Weight | Light | Very heavy |
| Cost per kWh (2026) | ~R2,500–R3,500 | ~R1,200–R1,800 |
| Lifespan | 10–15 years | 3–5 years |
| Verdict | Better value long-term | Lower upfront cost only |
Lithium LiFePO4 costs more upfront but the cost per cycle over its lifespan is dramatically lower. For daily load shedding cycling, gel batteries wear out in 2–3 years. Lithium is the only practical choice for serious daily use.
Rough 2026 Cost Estimates
| Setup | What it covers | Approx installed cost |
|---|---|---|
| 3kVA inverter + 5kWh LiFePO4 | Lights, fridge, TV, WiFi — 4–6 hours | R45,000–R65,000 |
| 5kVA inverter + 10kWh LiFePO4 | Full essential load including laptop + AC (limited) | R80,000–R110,000 |
| 8kVA inverter + 20kWh LiFePO4 | Near-full house, extended outages | R150,000–R200,000 |
These are supply + installation estimates for 2026 in Gauteng. Western Cape and KZN prices are typically 5–15% higher. Always get three quotes.
Do You Need Solar Panels Too?
A battery-only system (no solar panels) will run you through load shedding but needs to recharge from the grid when power returns. This is a valid and cheaper option if your primary goal is just outage backup. Adding solar panels means the battery charges from sunlight during the day and you can potentially be grid-independent for large portions of the day — not just during load shedding.
For most South African households dealing with load shedding, the sweet spot is a hybrid system: solar panels + battery + grid connection. The solar charges the battery during the day; you use battery during outages and evenings; grid top-up covers what solar can't produce.
Calculate exactly what you need
Use our load shedding backup sizer to select exactly which appliances must stay on, set your outage duration, and get a precise battery capacity recommendation with 2026 cost estimates.
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