Generator Sizing Calculator
Find out what size generator your home needs during load shedding, including running costs and diesel vs petrol comparison
Select the appliances you need to run during load shedding. The calculator adds 20% headroom and recommends the minimum generator size.
Generator Sizing Results
Sizing based on SANS 10142-1 wiring regulations. Add 20% headroom per standard engineering practice. Installation must be done by a licensed electrician with a Certificate of Compliance. Generator must comply with local noise bylaws (typically 65 dB(A) at 7m). Secure storage of fuel: max 200L diesel/petrol in SABS-approved containers on residential premises.
Generator Sizing and Installation in South Africa SANS 10142 · Load shedding · Fuel storage
Load Shedding Context
South Africa's load shedding programme — Eskom's controlled power cuts to manage national grid demand — has become a permanent fixture of SA life. Stages 1 to 2 mean 2–4 hours of outages per day; Stage 4 means up to 8 hours. Stage 6 (the highest implemented) means up to 10–12 hours of daily outages spread across multiple slots. For households and small businesses, a backup generator or solar-battery system is increasingly essential infrastructure rather than optional.
How Generator Sizing Works
Generator capacity is rated in kVA (kilovolt-amperes), which relates to kW (kilowatts) through the power factor: kW = kVA × power factor (typically 0.8). When selecting a generator:
The 20% headroom accounts for inrush current when motors start (fridges, pool pumps, gate motors draw 3–6× their running current at startup), generator thermal derating in hot weather, and future load growth. Undersizing a generator is the most common and costly mistake — it leads to overloading, voltage instability, and premature engine failure.
SANS 10142-1 Electrical Installation Requirements
Any generator connected to your home's electrical system in South Africa must comply with SANS 10142-1 (The wiring of premises). The key requirement is a transfer switch (changeover switch) — a mechanical or automatic device that physically disconnects your home from the Eskom supply before connecting the generator. Failure to install a transfer switch creates a potentially lethal backfeed hazard for Eskom workers and is illegal. A licensed electrician must install the transfer switch and issue a Certificate of Compliance (COC).
- Manual transfer switch: R2,000–R5,000 + installation
- Automatic transfer switch (ATS): R4,000–R12,000 + installation
- COC required for insurance purposes and property sale
Noise Regulations
Municipal noise bylaws typically limit generator noise to 65 dB(A) measured at the boundary of a residential property, and many municipalities require generators to be switched off between 22:00 and 06:00. In practice, a standard open-frame generator produces 65–75 dB(A) at 7 metres. Options to reduce noise include a canopied (silent-type) generator, a soundproof enclosure, or acoustic barriers. A canopied unit typically costs 30–50% more than the equivalent open-frame model.
Fuel Storage Rules
The Dangerous Goods Act limits residential petrol storage to 200 litres in approved containers. Diesel storage limits are more lenient but storage must comply with SANS 10228. Use SABS-marked metal or HDPE containers. Never store fuel inside the home or garage. A 5 kVA generator running 4 hours per day consumes approximately 5–8 litres, requiring a 25L can refill every 3–5 days during Stage 4 loadshedding.
Frequently Asked Questions
What size generator do I need for my house in South Africa?
For essential loads only (lights, fridge, TV, WiFi, and a kettle), a 5 kVA generator is typically sufficient for a medium-sized household. If you want to run a geyser or pool pump, upgrade to 8–10 kVA. Calculate your specific loads using the checkbox tool above, add 20% headroom, and divide by 0.8 to get the required kVA rating.
Is diesel or petrol better for a home generator in SA?
Diesel generators are 20–30% more fuel-efficient, have longer engine life (3,000–5,000 hours vs 1,500–2,000 for petrol), and diesel is generally safer to store. The downside is higher initial cost and diesel availability in some rural areas. Petrol generators are cheaper upfront and widely available, but cost more to run long-term. For regular use (Stage 4+), diesel usually pays back the price premium within 1–2 years.
Do I need a permit or COC for a generator in South Africa?
Yes. If the generator is connected to your home's electrical installation (even via a plug), a licensed electrician must install a transfer switch and issue a Certificate of Compliance under SANS 10142-1. Without a COC, your insurance may be invalid and you could be liable for any harm caused by backfeed into the Eskom network. Some municipalities also require notification or registration.
Generator vs solar with battery — which is better for loadshedding?
For Stage 1–4 loadshedding (2–8 hours/day), a solar-plus-battery system is usually the better long-term investment: silent, no fuel cost, no maintenance, and it adds property value. A 5 kW solar system with 10 kWh lithium battery costs R120,000–R180,000 but has near-zero running costs. A 5 kVA generator costs R20,000–R35,000 but at R22/L diesel and 4 hours/day you spend R500–R700/month in fuel. Solar pays back in 4–6 years. For Stage 6 or off-grid scenarios, a combination (solar primary, generator backup) is optimal.
How do I protect my generator from theft in South Africa?
Generator theft is endemic in South Africa — a R30,000 generator is highly desirable target. Essential security measures include: a heavy-duty welded steel security cage (R3,000–R8,000), anti-theft ground anchors bolted to a concrete slab, a chain and disc lock on the fuel cap, GPS tracking device, and perimeter lighting with motion sensors. Record the serial number and register it on the SAPS database. Ensure your home insurance policy specifically covers portable generators — many standard policies exclude them or have low sub-limits.