What Size Inverter Do You Need for Load Shedding? The Complete SA Guide
The right inverter size depends on which appliances you want to run and how long you need them to last. Here's exactly how to size your system for any load shedding stage.
Quick Answer: Common Inverter Sizes
- 1–2 kVA: Lights, router, phone charging, small TV
- 3 kVA: Lights + router + fridge + TV + phone charging (most common)
- 5 kVA: Everything above + microwave, washing machine
- 8–10 kVA: Full home — includes geyser, stove, AC (requires large battery bank)
How to Calculate Your Inverter Size
The formula is simple: add up the wattage of all appliances you want to run simultaneously, then multiply by 1.25 (a safety factor for surge current when motors start up).
For example, if you want to run:
- LED lights: 10W × 10 = 100W
- Fridge: 150W
- TV: 100W
- Router: 10W
- Phone chargers: 10W × 2 = 20W
Total: 380W × 1.25 = 475W → round up to a 1 kVA inverter (minimum standard size is 1 kVA). If you add a kettle (1500W), you'd need a 3 kVA inverter.
Battery Sizing Guide
Once you know your inverter size, size the battery based on your backup hours:
- Stage 1–2 (2–4 hours off): 2–4 hours of backup needed
- Stage 3–4 (4–6 hours off): 4–6 hours of backup needed
- Stage 5–6 (6–8 hours off): 6–8 hours of backup needed
Battery Ah = (Watts × Hours) ÷ (Voltage × Depth of Discharge)
For a 3 kVA inverter running 400W for 4 hours on a 48V LiFePO4 battery (80% DoD):
400W × 4h ÷ (48V × 0.8) = 33 Ah → round up to 2 × 100Ah batteries
LiFePO4 vs Lead-Acid: Which Battery?
| Type | Lifespan | Depth of Discharge | Verdict |
|---|---|---|---|
| LiFePO4 (Lithium) | 10–15 years | 80% | ✅ Best choice |
| Lead-acid (AGM) | 2–4 years | 50% | ⚠️ Poor value long-term |
Need to calculate your exact inverter size?
Use our free Inverter & Battery Calculator — select your appliances and get instant recommendations.
Try the Inverter Calculator →Electricians: Using This for Client Quotes
If you're an electrician or solar installer, use these calculators to size systems for your clients. Then send professional quotes and invoices with The Trade Kit — free invoicing and job management built for SA tradespeople.
Key Takeaways
- For most homes, a 3 kVA inverter with 5–10 kWh battery is the sweet spot
- Always add a 25% safety margin when sizing inverters
- Use LiFePO4 batteries — they last 3–5× longer than lead-acid
- For Stage 4–6 load shedding, plan for 4–6 hours of backup
Electrician or solar tech?
Size the backup, then send a professional invoice — built for SA trades.