What Will a 5kWh Battery Power (and for How Long)?
By SolarGuide10 min read
If an inverter answers "how much can I run at once," a battery answers the question everyone actually asks during load-shedding: "how long until the lights go out?" A 5kWh battery is one of the most common sizes in South African homes, and the honest answer to what it will power is refreshingly simple. It holds five kilowatt-hours of energy, and you spend that budget at whatever rate your appliances demand.
The catch is that the rate varies wildly. Run only the essentials and 5kWh stretches across most of an evening. Boil kettles, run a geyser element and bake in the oven, and you can drain the same battery in under an hour. Understanding a 5kWh battery is really about that trade-off between what you run and how long it lasts, and this guide gives you the arithmetic to work it out for your own home.
5.32 kWh
usable storage
90%
usable depth
6,000
charge cycles
Key takeaways
A 5kWh battery stores five kilowatt-hours: draw 1,000 watts steadily and it lasts roughly five hours.
Usable capacity is slightly less than the label, and lithium (LiFePO4) gives you far more of it than lead-acid.
Light essential loads stretch a 5kWh battery across a whole load-shedding evening.
Heavy heating appliances drain it fast; that's a runtime problem, not an inverter problem.
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The one formula that explains everything
Battery runtime comes down to a single relationship: energy divided by power equals time. A 5kWh battery holds 5,000 watt-hours. Divide that by how many watts you are drawing, and you get roughly how many hours it lasts.
Draw 500 watts (a very realistic "essentials only" load of lights, Wi-Fi, TV, fridge and chargers) and 5,000 ÷ 500 gives you about ten hours in theory. Draw 1,000 watts and you get around five hours. Draw 2,500 watts by running a kettle and an oven together, and the same battery empties in roughly two hours. Same battery, wildly different answers, because the only thing that changed was your draw.
This is why two neighbours with identical 5kWh batteries report completely different experiences. One runs essentials and sails through load-shedding; the other cooks dinner on electricity mid-outage and wonders why the battery "died."
Usable capacity: the number under the number
A 5kWh battery does not hand you a full 5kWh every time. Two things reduce the figure you can actually use.
First, depth of discharge. Batteries are healthiest when you don't run them to absolute zero. Modern lithium iron phosphate (LiFePO4) batteries, the standard in quality SA installs, allow very deep discharge, commonly 90–100%, so you get most of the label. Older lead-acid batteries only wanted about 50% discharge to survive, meaning a "5kWh" lead-acid bank gave you closer to 2.5kWh usable. This alone is why lithium has become the default for load-shedding.
Second, conversion losses. Turning stored DC into household AC through the inverter is efficient but not perfect, so a small slice is lost as heat. The practical upshot: plan around a lithium 5kWh battery giving you somewhere in the region of 4.5kWh of genuinely usable energy, and treat that as your working budget.
What 5kWh runs, appliance by appliance
Let us spend the budget on real appliances so you can picture it.
Your background essentials (LED lights, Wi-Fi, a TV, security, phone and laptop charging, and a fridge-freezer) typically total 300–600 watts. On that alone, a usable ~4.5kWh battery runs for roughly seven to fifteen hours, comfortably covering even a long or double load-shedding slot.
Now add the heavy hitters, and watch the budget drain:
An electric kettle at ~2,000 watts for two minutes uses about 0.07kWh. Trivial per boil, but it's the simultaneous draw that matters if paired with other items.
A geyser element at ~3,000 watts running for an hour eats about 3kWh, well over half your battery in one go.
An oven at ~2,000 watts for 45 minutes uses about 1.5kWh.
A microwave for ten minutes, a washing machine cycle, or a tumble dryer load each take a meaningful bite.
A single mid-sized air conditioner at ~1,000 watts running for two hours uses about 2kWh, nearly half the battery.
The pattern is unmistakable. Electronics and lighting cost almost nothing over time; anything that heats, dries or cools costs a lot. A 5kWh battery is generous for keeping a home livable through outages and stingy if you try to run a full electric kitchen off it.
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You have more control over runtime than you might think, and none of it requires a bigger battery.
The biggest lever is shifting heavy loads to daytime solar. If your panels heat the geyser, run the pool pump and handle the cooking while the sun is up, that energy never touches the battery; the battery is reserved for evening and outage essentials. This single habit transforms how far 5kWh goes.
The second lever is avoiding electric heating during outages. Boil water on gas, cook on gas or a small camping stove during a long stage, and dry laundry on the line. You are not depriving yourself; you are simply not spending kilowatt-hours on the most expensive tasks when the grid is down.
The third is recharge cadence. Between load-shedding slots, your panels and the grid top the battery back up. A 5kWh battery that fully recovers between slots effectively gives you its capacity again and again through the day. If your panels are undersized or slots come back to back, recharge becomes the bottleneck, which is why battery, inverter and panels must be sized as one system. Get a free Alumo quote →
Which package gives you 5kWh?
Alumo's Gold "The Power Bae" sits closest to this bracket: a Sunsynk 5kW inverter with a 5.32kWh battery and six panels, from around R2,423/month, quoted at roughly five hours of backup for a typical essential load. That runtime figure is exactly the kind of estimate this guide explains: it assumes sensible essentials, not a full electric kitchen running flat out.
If you want something leaner, the BrightStart rent-to-own pairs a Solis 5kW with an Eenovance 5.3kWh battery from about R1,339/month over seven years, a similar energy budget on a longer, lower-monthly finance structure. The battery size is comparable; the difference is the finance and the panel count feeding it.
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5.0 kWh
Estimated backup time
12.9 hours
Running about 350 W
Rough estimate at ~90% usable depth. Real runtime depends on the exact appliances and battery. A quote sizes it properly.
How long does a 5kWh battery last during load-shedding?
It depends entirely on your draw. On essential loads of around 400–600 watts (lights, Wi-Fi, TV, fridge, chargers) a usable 5kWh lithium battery lasts roughly seven to twelve hours — easily covering a standard slot. Run heavy heating appliances and it can empty in one to two hours. Energy divided by power equals time.
Can a 5kWh battery run a fridge overnight?
Comfortably. A modern fridge-freezer averages well under 200 watts once running, so it uses only 1–2kWh across a full night. A 5kWh battery can run a fridge overnight and still have plenty left for lights, Wi-Fi and security, provided you are not also running heavy appliances.
Is a 5kWh battery enough for my house?
For keeping a typical home's essentials running through load-shedding, a 5kWh battery is enough for many households. If you want to run heavy appliances like ovens, geysers or multiple air conditioners during outages, or you face frequent back-to-back stages, you may want more capacity. A site assessment matches the size to your real usage.
What is the difference between a 5kWh battery and a 5kW inverter?
They measure different things. The 5kWh battery is energy storage — how long you can run. The 5kW inverter is a power rating — how much you can run at once. You need both correctly sized: the inverter sets the ceiling on simultaneous load, the battery sets how long that load can last.
Who works out the right battery size for me?
SolarGuide is an independent referral partner. Alumo carries out the site assessment and supplies, installs, finances and warrants the system, sizing the battery and inverter to your real demand. 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.
