Come the height of a Durban summer or a Highveld heatwave, one question dominates the solar conversation. Can it run the aircon? It's a fair thing to worry about. Air conditioning has a reputation as a power glutton, and plenty of people assume it sits outside what home solar can handle. The reality is better than the reputation, though it comes with conditions you need to understand before you buy.
The short version is yes, solar can run air conditioning in South Africa, and modern inverter aircons make it far more practical than the old assumptions suggest. What matters is which aircon, how many at once, and for how long, because cooling is energy-hungry over time even when its instantaneous draw is modest. Get the sizing right and you can stay cool through the worst of a heatwave and load-shedding. Get it wrong and you'll drain a battery in an hour.
Key takeaways
Yes, solar can run air conditioning, especially modern inverter (DC) aircons that draw far less than old fixed-speed units.
A typical mid-size inverter aircon draws roughly 800–1,500 watts running, well within a 5kW inverter's reach.
The real cost is energy over time (kWh), so battery size and daytime solar matter more than inverter size.
Running aircon off surplus solar during the day is the smartest, cheapest way to stay cool.
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Old aircons versus inverter aircons
The single biggest factor in whether solar can run your cooling is which type of air conditioner you have. This is where most of the old "aircon kills solar" folklore comes from.
Traditional fixed-speed air conditioners work like a light switch. The compressor slams on at full power, cools to the set temperature, switches off, then slams back on again. Each of those start-ups draws a heavy surge, and the unit runs at full draw whenever it's on. That start-stop cycling is hard on both a battery and an inverter.
Modern inverter (DC) air conditioners work differently. The compressor ramps smoothly and then modulates, running at a low, steady output to hold a temperature rather than repeatedly blasting to reach it. Once a room is cool, an inverter aircon can trundle along drawing only a few hundred watts. There's no punishing surge, just a gentler, more predictable load, which is exactly what a solar-and-battery system likes. If you're buying an aircon with solar in mind, an inverter model is close to essential.
The real numbers
Let's put figures to it. A typical mid-size inverter split unit, say a 12,000 BTU (about 3.5kW cooling) model sized for a bedroom or small living room, draws roughly 800–1,500 watts while actively cooling, and considerably less once it's just maintaining temperature. A smaller 9,000 BTU unit sits lower. A large 24,000 BTU unit for an open-plan living area can pull 2,000 watts or more.
Power is the easy part
On the power question, meaning can the inverter deliver enough watts at once, the answer is comfortably yes for most homes. A 5kW inverter has ample headroom to run one mid-size aircon alongside your normal essentials. Even two units are feasible on 5kW, provided you're not also running a kettle, oven and geyser element at the same moment. Power is rarely the binding constraint for household aircon.
Energy over time is the real question
The harder question is energy. An inverter aircon holding a room at temperature might average 700–1,000 watts. Run it for four hours and you've used roughly 3–4kWh. That's most of a 5kWh battery spent on cooling alone. Run two units all evening and you'll need substantially more storage. Aircon doesn't overwhelm your inverter. It quietly empties your battery. This is why the sizing conversation for cooling is really a battery and panel conversation.
800–1,500W
mid-size aircon running
3–4kWh
four hours cooling
5kW
inverter headroom
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Here's the point that changes everything. The best time to run air conditioning is exactly when your panels are producing the most, in the hot, sunny afternoon. You don't have to engineer that. It's the natural alignment of South African weather and solar output.
When the sun is blazing and your roof is generating surplus power, running the aircon off that surplus costs you almost nothing and doesn't touch your battery at all. You're cooling the house on energy you'd otherwise waste or export. A well-designed system with enough panels can carry a daytime cooling load comfortably while still charging the battery for the evening.
Pre-cooling takes this further. Drop the house temperature in the afternoon while solar is abundant, close it up well, and it coasts cooler into the evening with far less aircon needed after sunset. Add good ceiling insulation, shaded windows and closing up at the hottest part of the day, and you cut the cooling energy your battery has to supply overnight. Staying cool on solar is as much about smart timing and a well-sealed home as it is about kilowatts. Get a free Alumo quote →
Sizing a system that runs aircon
If cooling is a priority for you, design it in from the start rather than bolting it on afterwards. Three things matter.
Enough panels to carry the daytime cooling load and charge the battery. Cooling is a big daytime consumer, so you want generation to spare. Enough battery if you insist on aircon after dark, remembering that every evening hour of cooling is roughly a kilowatt-hour gone. And an inverter with comfortable headroom so the aircon plus your other loads never crowd the ceiling. The most cost-effective approach is usually to run the aircon freely off solar during the day and keep only light essentials on battery at night. That keeps you cool through heatwaves without paying for an enormous battery.
Which package suits aircon?
For running a single mid-size inverter aircon comfortably during the day, Alumo's Gold "The Power Bae" is a sensible starting point: a Sunsynk 5kW inverter, 5.32kWh battery and six panels from around R2,423/month. Its 5kW ceiling and six-panel array give you the daytime generation and power headroom to cool a main living space while the sun is up, with essentials covered at night.
If you want to run multiple aircons, or keep cooling going deep into the evening, you'll likely want more panels and battery than any standard package includes, so a custom design. That's exactly the kind of load a site assessment is built to size, because your climate zone, home insulation and cooling habits all feed into the answer.
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Yes. A typical mid-size inverter aircon draws around 800–1,500 watts while cooling, so a 5kW inverter runs one comfortably alongside normal household loads, and often two if you are not also running heavy kitchen appliances. The limiting factor is usually battery energy over time, not the inverter's power rating.
How long can I run aircon on a solar battery?
It depends on the unit and battery size. An inverter aircon averaging around 800–1,000 watts uses roughly 3–4kWh over four hours, which is most of a 5kWh battery. Running aircon off daytime solar instead of the battery is far more efficient, and pre-cooling the house while the sun is up reduces how much you need after dark.
Do I need a special "solar aircon"?
No. Any modern inverter (DC) air conditioner works well with solar; you don't need a special product. What matters is choosing an inverter-type unit rather than an old fixed-speed one, because inverter aircons draw a smooth, lower load without the heavy start-up surges that strain batteries and inverters.
Is it cheaper to run aircon on solar than Eskom?
Running aircon off your own surplus solar during the day is effectively free once the system is paid off, versus paying Eskom's tariff, which keeps climbing. Running it off battery at night uses stored energy you could spend elsewhere, so daytime cooling is the most cost-effective approach. Over time this is one of the ways solar reduces your bill.
Who sizes a system to run my air conditioning?
SolarGuide is an independent referral partner. Alumo carries out the site assessment and supplies, installs, finances and warrants the system, sizing panels, battery and inverter to your cooling needs and climate. All pricing here is indicative and subject to that assessment and credit approval; we simply help you compare and get a free quote. Get a free Alumo quote →
SolarGuide is an independent referral partner. We help you compare options and arrange a free quote — Alumo supplies, installs, finances and warrants the systems. Pricing is indicative, sourced from Alumo’s published catalogue, and subject to a site assessment and credit approval.
