Inverter & Battery Calculator

What size inverter do I need for my home in South Africa?

The right inverter size depends on which appliances you want to run simultaneously during load shedding. Add up the running wattage of each appliance and multiply by 1.25 to get the minimum inverter size (the safety margin covers momentary surge). A typical home running a fridge, lights, router, TV, and laptop needs a 3kW inverter. Add a kettle or microwave and you need 5kW. Our calculator does this automatically — just select your appliances.

How much battery capacity do I need for load shedding?

Battery capacity (in kWh) depends on your total load and how long the outage lasts. The formula is: battery kWh = (total watts ÷ 1000) × backup hours ÷ 0.8. The 0.8 accounts for the 80% depth of discharge (DoD) of lithium (LiFePO4) batteries — you should not discharge below 20% to protect battery life. For example, a 1 kW load for 4 hours needs 5 kWh of usable energy, which means a 6.4 kWh battery bank (6.4 × 0.8 = 5.12 kWh usable).

How many solar panels do I need to recharge my inverter battery?

A 550W solar panel generates approximately 2 kWh per day in South Africa (using 5 peak sun hours and 75% system efficiency). So if you use 4 kWh during a 4-hour Stage 4 outage, you need 2 panels to fully recharge the battery the next day — assuming a full day of good sunlight. More panels mean faster recharging and greater savings on your Eskom bill.

Can I run a kettle or microwave on an inverter?

Yes, but these appliances draw very high wattage — a kettle typically uses 2,000W and a microwave 1,200W. To run either, you need an inverter rated at least 3kW (for a microwave) or 3kW+ (for a kettle, accounting for the safety margin). The key point is that while they draw a lot of power, kettles and microwaves are used for very short periods — so the energy impact on your battery is smaller than continuous loads like a fridge.

Can I run an air conditioner on an inverter?

Yes, but it requires careful planning. A 9,000 BTU (2.6kW) air conditioner draws roughly 900W running, but at startup the motor can surge to 3–4× that for a fraction of a second. You need an inverter with sufficient surge capacity — typically a 5kW hybrid inverter for a 9,000 BTU unit. Inverter-type air conditioners (which vary their compressor speed) have significantly lower startup surge than fixed-speed units and are the better choice for battery backup.

How much does a home solar inverter system cost in South Africa?

A basic inverter + battery backup system (no solar) starts at around R20,000–R35,000 for a 3kW inverter with a 5.12kWh LiFePO4 battery, including installation. A mid-size system — 5kW inverter, 10.24kWh battery, and 4–6 solar panels — typically costs R55,000–R90,000 installed. Full solar with larger battery banks can exceed R120,000. Prices vary significantly by brand, supplier, and installer. Always get at least 3 quotes.

What is the difference between a kW and kVA for an inverter?

kVA (kilovolt-amperes) is apparent power — the total electrical load. kW (kilowatts) is real power — the actual useful work done. The relationship is: kW = kVA × power factor (PF). Most home appliances have a power factor of 0.8, so a 5kVA inverter delivers 4kW of real power. Modern hybrid inverters are increasingly rated in kW. When comparing inverters, use the kW rating for apples-to-apples comparisons.

How long do solar panels last in South Africa?

Quality solar panels (Tier 1 brands like JA Solar, Canadian Solar, Risen, LONGi) are warrantied for 25–30 years at 80% of rated output. In South African conditions — high UV intensity and occasional hail — real-world lifespan is typically 20–30 years with regular cleaning. Most panels will still produce 80–85% of their original output after 25 years. The inverter typically needs replacement after 10–15 years; batteries after 10–15 years (LiFePO4 is rated for 3,000–6,000 charge cycles).