Solar vs Inverter vs Generator: The Real Cost of Backup Power in South Africa (2026)
A numbers-first 2026 comparison of inverter+battery, full solar PV, and a generator — capex, cost per kWh, lifespan, and a real 10-year payback.
Published 2026-06-01 · Updated 2026-06-29
Three different machines solving three different problems
Before you compare prices, understand that these are not three versions of the same product. An inverter+battery is a grid-shifting device: it buys electricity from the municipality when the grid is up, stores it, and re-delivers it when the grid is down. It generates nothing. A full solar PV system with a battery is a power plant: it makes its own electricity from the sun and can both back you up and cut your monthly bill. A petrol or diesel generator is a fuel-burning engine that makes electricity on demand and stores nothing. Each one has a completely different cost structure, and that is why the 'cheapest' option flips depending on how you use it.
The single number that separates them is running cost per kilowatt-hour (kWh). A generator delivers power at roughly R23/kWh once you account for petrol at about R23/litre and the fact that a small genset burns roughly two litres an hour to deliver around two usable kilowatts. An inverter+battery delivers stored grid power at about R4.80/kWh — the municipal tariff (we model R3.30/kWh) divided by round-trip efficiency, plus the wear-and-tear amortisation of the battery itself. Self-generated solar comes in cheapest by a wide margin, around R1.20/kWh over the system's life, because the fuel is free. Hold those three numbers in your head: roughly R23, R4.80 and R1.20 per kWh. They drive everything below.
This is general information, not personalised financial advice — your tariff, sun exposure and outage pattern will move the numbers. But the relationships hold: a generator is the cheapest to buy and the most expensive to run, solar is the most expensive to buy and the cheapest to run, and an inverter+battery sits in the middle on both.
Upfront capex: what you actually pay to walk in the door
A petrol generator in the 4–5kW class is the cheapest entry point at around R18,000 for the unit, plus a few thousand more if you want it wired into the house through a changeover switch rather than running extension leads. That low sticker price is exactly why generators sell during every bout of load-shedding — the pain of buying is small and immediate relief is guaranteed.
A 5kW inverter paired with a 5kWh lithium-iron-phosphate (LiFePO4) battery, professionally installed with a certificate of compliance, lands at roughly R55,000. About R30,000 of that is the battery — the single most expensive and most perishable component in any backup system. A full solar setup is the heavy lift: a 5kW hybrid inverter, a 5kW solar array (around twelve to fourteen panels), a 10kWh battery and the mounting, wiring and CoC together run to roughly R150,000 installed. That is nearly three times the inverter-only price and over eight times a generator, and it is the number that scares most households out of the option that is actually cheapest to run.
The capex gap is the whole game. You are deciding whether to pay R18,000 and bleed money on fuel forever, pay R55,000 and shave your outage costs, or pay R150,000 up front to stop buying daytime electricity almost entirely. Which one wins depends entirely on how many hours you run it and for how many years — which is why a single 'price' comparison is useless and a total-cost-of-ownership comparison is the only honest one.
Lifespan, maintenance and the noise nobody budgets for
Lifespan is where the generator's cheap sticker price unravels. A consumer-grade petrol generator that gets real use — several hours during every outage — typically lasts three to five years before it needs a serious rebuild or replacement, and it demands oil changes, air-filter cleaning and fuel stabiliser to get even that. A modern hybrid inverter is rated for ten years or more, and a quality LiFePO4 battery is rated to roughly 6,000 cycles. At one cycle a day that is about sixteen years of calendar life, so in a normal 10-year horizon you should not need to replace it once. Solar panels routinely carry 20–25 year performance warranties and lose only a fraction of a percent of output per year.
Maintenance cost tracks the same pattern. A generator wants around R1,500 a year in oil, filters and servicing, and that is before fuel. An inverter+battery system is close to maintenance-free — there are no moving parts, just an occasional firmware update. A solar array needs the panels rinsed of dust a couple of times a year, call it R1,000 annually, and nothing else. Over ten years the generator quietly accumulates the most service spend of the three despite being the cheapest to buy.
Then there is the part no spreadsheet captures until you live with it: noise and practicality. A generator is loud — 65 to 75 decibels at a few metres, roughly a running vacuum cleaner that does not stop — it smells of petrol, it must run outside in ventilated space, it cannot run unattended overnight, and you have to physically start it and feed it fuel every single time the lights go out. An inverter and a solar system are silent, automatic and invisible; the power simply does not drop. For a family that loses power at 2am or while no one is home, that automatic, silent switchover is worth real money even though it never shows up on a fuel receipt.
The 10-year total-cost-of-ownership, worked in rands
Take a typical home that needs to back up about 5kWh of essential daily load — lights, Wi-Fi, TV, fridge, phone chargers and a few plugs — across an average load-shedding pattern. Over ten years that is roughly 18,250 kWh of energy that has to come from somewhere other than the grid during outages. Now run each option through capex plus running cost plus replacements.
The petrol generator looks cheapest on day one and is the most expensive by a mile by year ten. Capex is R18,000, but at R23/kWh the fuel alone for 18,250 kWh is about R420,000. Add roughly R18,000 for one mid-life replacement and R15,000 in servicing over the decade, and the 10-year total lands near R471,000. The inverter+battery system costs R55,000 up front, and at a blended R4.80/kWh its energy over ten years is about R87,000, with no battery replacement needed inside the horizon — a 10-year total of roughly R142,000. The full solar system has the highest capex at R150,000 but the lowest running cost: it generates around 17.6kWh on a good day, far more than the 5kWh of essentials, so it both covers outages and slashes your daytime grid purchases. With about R10,000 of cleaning over ten years and no battery replacement, its 10-year total is roughly R160,000 — and that figure ignores the thousands of rands of grid electricity it saves you every year, which we get to next.
Line them up: generator R471,000, inverter+battery R142,000, solar R160,000 (before bill savings). The generator is more than three times the cost of either alternative over a decade, purely because fuel at R23/kWh dwarfs everything. The inverter+battery is the lowest pure-backup cost. Solar is a hair more than the inverter on backup alone — but it is the only option that also earns money back month after month, which is what makes its true position the strongest once you stop treating it as 'just' backup.
When each option actually wins, and how to size it
The generator wins in exactly one scenario: rare, short, infrequent use where the low capex is never overtaken by fuel cost. If you lose power a handful of times a year for a few hours, a R18,000 generator you run for thirty hours annually is the rational buy — you will never burn enough fuel for the cheaper-per-kWh options to catch up. The moment usage becomes routine, the generator becomes the worst financial choice on the page. The inverter+battery wins when you have frequent outages but cannot or do not want to spend R150,000 — it gives you silent, automatic backup at a third of the solar capex, and it is the right call for flats, rentals, or homes with poor roof orientation where panels make little sense. Full solar wins whenever you have a north-facing roof, a long time horizon, and a meaningful daytime electricity bill, because only solar attacks both problems — outages and your monthly account — at once.
Sizing starts with your essential load, not your whole house. Walk the home, list only what must stay on during an outage, and add up the watts: LED lights (a few hundred watts), Wi-Fi and a laptop (~100W), a fridge (~150W average, with a higher start-up surge), a TV and decoder (~150W). Most homes land at 800W–1,500W of essential continuous load. Multiply by the hours you need to ride through to get your kWh — two hours of 1kW is 2kWh, and a realistic essentials budget is the 5kWh/day we modelled. Your battery must hold at least that usable energy (remember you only use about 90% of a battery's rated capacity), and your inverter must handle the peak surge when the fridge and microwave kick in together. Do not size for the geyser, oven, kettle or pool pump on battery — those are grid or daytime-solar loads, and trying to back them up is what blows budgets.
A correctly sized 5kW inverter with a 5kWh battery comfortably carries a 5kWh essential day. A 5kW solar array with a 10kWh battery does the same and banks surplus sun to offset your bill. Oversizing the battery is the most common and most expensive mistake — every extra kWh of LiFePO4 is roughly R6,000 you may never cycle. Size to the essentials, not the fantasy of running everything.
The real payback — not the marketing one — and how to run your own
Installers quote a 'payback' by taking the total energy your panels could generate and multiplying by your tariff. For our R150,000 solar system generating about 6,400kWh a year at R3.30/kWh, that gives a tidy 7-year payback. The problem is the word 'could'. Without a battery big enough to soak up every surplus kWh and without a feed-in tariff that pays you fairly for exports, you only actually use a portion of what the panels make — realistically around 65% self-consumption for a typical home. The rest is generated at noon when nobody is home and is effectively clipped or exported for little. Recompute on the energy you genuinely displace — about 4,200kWh a year, saving roughly R13,800 — and the honest payback stretches to about 11 years, not 7. Same system, same panels; the difference is whether you count electrons you produce or electrons you actually use.
The inverter+battery has its own honest-payback logic, and it is far quicker. Its 'return' is not a lower bill — it shifts grid energy, it does not make new energy — its return is avoiding the alternative cost of backup. If the realistic alternative is running a generator at R23/kWh, then every 4kWh of essential energy the inverter delivers per outage day at R4.80/kWh saves you roughly R18 a kWh versus the genset. Across a year that is real money, and the inverter can 'pay back' against a generator in under two years. The lesson is that payback is meaningless until you state what you are comparing against and which kWh you are actually counting — the marketing number almost always uses the most flattering version of both.
This is exactly the calculation the solar calculator is built to do honestly. Plug in your real tariff, your essential load, your outage hours, your roof's sun exposure and your self-consumption, and it will show you the capex, the cost per kWh, and the true payback for an inverter, a full solar system or a generator — side by side, with your numbers instead of an installer's. Run it before you sign anything: the difference between the marketing payback and the real one is often four or five years, and that is years of your money. Open the solar calculator and pressure-test your own decision.
Run the numbers yourself
Run your own load and payback numbers in the solar calculator
Open the toolFAQ
Is a generator or an inverter cheaper for load-shedding in South Africa?
A generator is far cheaper to buy — around R18,000 versus about R55,000 for a 5kW inverter with a 5kWh battery — but it is much more expensive to run. Generator power costs roughly R23/kWh in petrol, while an inverter delivers stored grid power at about R4.80/kWh. If you have outages regularly, the inverter wins overall within a couple of years; the generator only stays cheaper if you barely use it.
How long does a solar battery last and will I have to replace it in 10 years?
A quality LiFePO4 battery is rated to around 6,000 cycles, which at roughly one cycle a day is about sixteen years of life. In a normal 10-year ownership window you should not need to replace it. That is a major reason inverter and solar systems beat generators on total cost — a petrol generator typically needs a serious rebuild or replacement every three to five years.
What is the real payback period on a R150,000 solar system?
Installers often quote about 7 years by multiplying your panels' total possible generation by your tariff. The honest figure is closer to 11 years, because without a large battery or a fair feed-in tariff you only self-consume around 65% of what the panels make — the midday surplus is wasted. Always base payback on the electricity you actually use, not the maximum the panels could produce.
How do I size an inverter and battery for my essential load?
List only what must stay on during an outage — lights, Wi-Fi, fridge, TV, chargers — which for most homes totals 800W to 1,500W, or about 5kWh over a typical outage day. Your battery should hold at least that usable energy (you only use about 90% of rated capacity), and your inverter must handle the surge when appliances like the fridge start. Never size a battery for the geyser, oven, kettle or pool pump — keep those on the grid or on daytime solar.