Load Shedding Battery Sizing Guide for South Africa

Published March 2026 • 10 min read

Buying a battery backup system without first calculating your actual power needs is one of the most expensive mistakes South African homeowners make. Buy too little capacity and your lights go out halfway through a Stage 4 outage. Buy too much and you have spent tens of thousands of rand on capacity that sits unused. This guide walks you through the exact steps to size your battery bank correctly for South African load shedding conditions.

Step 1: Understand the Load Shedding Schedule

Before sizing your battery, you need to know the worst-case outage duration you are designing for. South Africa's load shedding stages work as follows:

Stage	Hours off per day (residential)	Outage blocks
Stage 2	~4 hours	2 x 2-hour blocks
Stage 4	~8 hours	4 x 2-hour blocks
Stage 6	~12 hours	6 x 2-hour blocks (or fewer longer blocks)
Stage 8 (theoretical)	~16 hours	Multiple long blocks

Most suppliers recommend sizing for a single worst-case outage block rather than 24-hour off-grid operation. In practice, even during Stage 6, your battery will recharge between blocks if your solar panels or grid is available. However, if you are in an area with multiple consecutive overnight outages, you need to size for that scenario.

Tip: Check your municipal load shedding schedule on the Eskom App or EskomSePush to understand the timing patterns in your area. Late-night blocks are the most disruptive as your battery has no solar to recharge during that period.

Step 2: Calculate Your Essential Loads

The first and most important step is deciding what you actually want to run during an outage. There are two approaches:

Whole-home backup: Run everything including your geyser, stove, air conditioner and pool pump. Requires a very large, expensive system (typically 10 kWh+ battery and 5 kVA+ inverter). Usually not cost-effective for pure load shedding backup.

Essential loads only: Run lights, selected plug points, TV, router, fridges and a few fans. Practical, affordable and covers the real annoyances of load shedding. This is what most systems are designed for.

List every appliance you want to run during an outage and find its wattage (on the rating label, in the manual, or via a plug-in energy meter):

Appliance	Typical Wattage	Hours used per outage	Energy (Wh)
LED lights (6 x 10W)	60 W	2 hrs	120 Wh
Refrigerator (A-rated)	80–150 W avg	2 hrs	160–300 Wh
LED TV (55 inch)	100–130 W	2 hrs	200–260 Wh
Wi-Fi router	10–20 W	2 hrs	20–40 Wh
Laptop charger	45–90 W	2 hrs	90–180 Wh
Phone chargers (3)	15–30 W	2 hrs	30–60 Wh
Ceiling fan (3 speed)	40–75 W	2 hrs	80–150 Wh
Security system + alarm	30–60 W	2 hrs	60–120 Wh
Gate motor (intermittent)	300 W peak, ~10 Wh/use	10 uses	100 Wh
Total (typical household)			~860–1310 Wh

Step 3: Apply the Battery Sizing Formula

Raw energy consumption is not the same as battery capacity required. You must account for:

Depth of Discharge (DoD): Lithium LiFePO4 can safely discharge to 80–90% DoD. Lead-acid should only discharge to 50% to protect battery life.
Inverter efficiency: Typically 90–95% for modern sine wave inverters.
Temperature derating: Battery capacity drops in cold weather (less relevant in most of SA but relevant in the Highveld winter).
Safety margin: Add 20–30% to allow for load growth and battery aging over time.

Required battery capacity (kWh) = (Daily energy use in Wh ÷ 1000) ÷ DoD ÷ inverter efficiency × safety margin Example (lithium, 2-hour outage): 1.1 kWh ÷ 0.85 DoD ÷ 0.93 efficiency × 1.25 safety = 1.74 kWh Example (lead-acid, 2-hour outage): 1.1 kWh ÷ 0.50 DoD ÷ 0.93 efficiency × 1.25 safety = 2.96 kWh

Key insight: This is why lithium batteries require less than half the physical capacity of lead-acid for the same usable energy. A 2 kWh lithium battery gives you more usable power than a 4 kWh (200Ah @ 12V) lead-acid bank in real-world conditions.

Step 4: Match Battery Capacity to Outage Duration

Using the typical household essential load of 1.1 kWh per 2-hour outage, here is a sizing reference for different outage durations:

Outage Duration	Energy Needed (kWh)	Lithium Battery Required	Lead-Acid Battery Required
2 hours (Stage 2)	~1.1 kWh	2 kWh (e.g., 1 x 2kWh LiFePO4)	3 kWh (250Ah @ 12V)
4 hours (Stage 4 — 1 block)	~2.2 kWh	3–4 kWh	6 kWh (500Ah @ 12V)
8 hours (Stage 4 — no recharge)	~4.4 kWh	5–6 kWh	12 kWh (1000Ah @ 12V)
12 hours (Stage 6 — no recharge)	~6.6 kWh	8–10 kWh	18+ kWh

For most suburban South African homes, a 5 kWh lithium battery system covers all Stage 4 scenarios comfortably, with enough capacity to bridge overnight Stage 6 blocks when combined with a 2–3 kWp solar array for daytime recharging.

Step 5: Size Your Inverter

Your inverter must handle the peak simultaneous load, not just the average. Add up the wattage of everything that might run at the same time, plus a 20% headroom:

Household Size	Essential Loads	Peak Simultaneous Wattage	Recommended Inverter
Flat / small apartment	Lights, fridge, TV, router, laptop	400–700 W	1 kVA (1000 VA)
Townhouse / 3-bed home	Above + security, fans, gate motor	800–1500 W	2–3 kVA
4–5 bed suburban home	Above + 2 fridges, pool pump intermittent	1500–3000 W	3–5 kVA
Small business / office	Computers, server, lights, comms	2000–4000 W	5 kVA

Watch out for motor starting loads: Fridge compressors, gate motors, pool pumps and air conditioners draw 3–6 times their rated wattage for 1–3 seconds on startup. Your inverter must handle this surge without shutting down. Always check the inverter's surge rating (usually 2–3x rated capacity for 5–10 seconds).

South African Market: What Does It Cost?

Battery backup system costs in South Africa (March 2026 approximate prices including installation):

System Size	Battery	Inverter	Approximate Installed Cost	Best For
Entry Level	1.2 kWh LiFePO4	1 kVA pure sine	R 12,000 – R 18,000	Flat, lights and router only
Standard Home	5 kWh LiFePO4	3 kVA	R 35,000 – R 55,000	3-bed home, all essentials
Large Home	10 kWh LiFePO4	5 kVA	R 65,000 – R 95,000	4-5 bed home, heavier loads
Hybrid Solar + Battery	5 kWh LiFePO4 + 3 kWp solar	5 kVA hybrid	R 85,000 – R 130,000	Full load shedding + bill reduction

These are ballpark figures. Get at least 3 quotes from reputable installers registered with the South African Photovoltaic Industry Association (SAPVIA) or the Association of Electrical and Mechanical Trades (AEMT). Be very wary of unusually low quotes — quality BMS (Battery Management Systems) and SANS-compliant electrical work are not cheap.

Common Battery Sizing Mistakes to Avoid

1. Forgetting the geyser: A standard 3 kW electric geyser running for 1 hour consumes 3 kWh — equal to an entire day's essential load. Never include the geyser in a load shedding backup system unless you have a very large solar installation. Switch to a gas geyser, solar geyser, or heat pump for hot water independence.

2. Undersizing for battery aging: All batteries lose capacity over time. A lithium battery that is at 80% of original capacity after 3 years of daily cycling is still functional, but your usable backup time is 20% shorter. Size with a 20–30% buffer from day one.

3. Buying cheap lead-acid for price: The lower upfront cost of flooded lead-acid (FLA) batteries is misleading. Their shorter lifespan (300–500 cycles vs 3000–6000 cycles for LiFePO4), higher maintenance requirements, and lower usable capacity make lithium more economical over a 10-year period in most South African load shedding scenarios.

4. Ignoring the charge rate: A 5 kWh battery charged by a 1 kW solar panel takes 5+ hours to fully charge. During Stage 6 with multiple blocks, your battery may not fully recharge between outages unless your solar array is appropriately sized. The solar array should be at least 50% of the battery kWh rating to maintain cycling during extended load shedding.

Conclusion: Size for Your Worst Realistic Scenario

The right battery size for South African load shedding is the one that covers your worst realistic outage scenario without excessive over-engineering. For most homes, that means designing for Stage 4 (a single 4-hour block without guaranteed recharge) with essential loads only. This typically lands in the 3–5 kWh lithium range, paired with a 2–3 kVA inverter.

Add solar panels to the system and you shift from pure load shedding backup to genuine energy independence, reducing your electricity bill while protecting against outages. That is where the real value lies in the South African context of persistently high Eskom tariffs and ongoing grid instability.