What Size Inverter Do I Need? Sizing for a Ghanaian Home or Office

Two numbers decide an inverter system, and they are independent of each other. The inverter rating decides what you can run at once. The battery bank decides how many hours you get. Buy a large inverter with a small battery bank and you can switch everything on for twenty minutes. Buy a small inverter with a huge bank and you will be sitting in the dark next to a full battery because the fridge tripped it.

Almost every disappointed inverter owner we meet in Ghana bought one number and not the other.

Step 1: list the load, in running watts

Write down only what you genuinely want working during an outage. Not everything in the house — the things whose absence actually matters.

Realistic figures for a Ghanaian household:

• LED bulbs — 7 to 12W each. Ten of them is around 100W
• Ceiling or standing fan — 60 to 80W each
• Television and decoder — around 100 to 150W together
• Wi-Fi router — 10 to 20W
• Laptop — 50 to 65W
• Phone chargers — 10 to 20W for several
• Refrigerator — 100 to 200W while the compressor runs
• Chest freezer — 150 to 250W while running
• Water pump — 370 to 750W for a typical domestic pump
• Microwave — 800 to 1,200W
• Electric iron — 1,000 to 1,500W
• Air conditioner, 1.5hp — 1,100 to 1,500W for an inverter-type unit, more for a conventional one

Use the rating plate on your own appliances where you can. These are planning figures, not measurements, and brands vary widely.

Add up only what runs at the same time

This is where people inflate their own systems unnecessarily. You will not iron while microwaving while pumping water. Add the things that genuinely coincide.

A typical evening in a three-bedroom house:

1. Lights, 100W
2. Three fans, 210W
3. TV and decoder, 150W
4. Router, laptop and chargers, 100W
5. Fridge, 150W

That totals 710W of running load.

Step 2: understand surge watts, because this is what trips inverters

Anything with a motor or a compressor draws far more current for the first fraction of a second than it does while running. A fridge at 150W running can pull well over 500W on start-up. A water pump can pull three to five times its rated figure.

The inverter must survive that momentary peak, not just the steady draw. This is the single most common sizing failure we are called out to fix: an inverter that carries the house perfectly until the fridge compressor kicks in, then shuts down.

So sizing has two tests, and both must pass:

• Can the inverter carry the total running watts continuously?
• Can it absorb the largest single surge on top of whatever else is already running?

Good inverters publish a surge or peak rating, often double the continuous rating for a few seconds. Ask for it. An inverter sold only with one headline number is hiding the half of the specification that matters to your fridge.

Step 3: convert watts to the kVA an inverter is sold in

Inverters, like UPS systems, are usually sold in kVA rather than watts. The conversion uses the power factor.

1. Take your total running watts — 710W from the example above
2. Divide by a power factor of 0.8 — 710 divided by 0.8 is about 890 VA
3. Add 25 to 30 percent headroom for surges and for the loads you have not thought of yet — around 1,150 VA
4. Round up to the next available size — a 1.5 kVA inverter

That headroom is not padding. It is what keeps the unit off its own limits, which is where inverters run hot and fail early. In a Ghanaian room that is running warm already, that matters more than it does in the manufacturer's test lab.

Three worked sizes

A small flat or a bedsit. Lights, a fan, TV, router and chargers. Around 350W running, no fridge. A 1 kVA inverter is comfortable.

A three-bedroom house, no air conditioning. The 710W example above, including a fridge. A 1.5 kVA inverter, sized so the fridge surge is absorbed.

A small office or shop. Ten LED panels, four workstations, a printer on standby, a router, a POS terminal and a water dispenser. Call it 1,400W running. Divided by 0.8 is 1,750 VA; plus 30 percent is about 2,275 VA, so a 3 kVA inverter.

Step 4: now size the battery bank, which sets your runtime

This is the second number, and it is where the real money sits. The arithmetic is straightforward.

To work out how long a bank will carry a load:

1. Battery capacity in watt-hours equals amp-hours multiplied by system voltage. Two 200Ah batteries in a 24V system give 200 times 24, which is 4,800Wh
2. Usable capacity is less than that. Depth of discharge matters enormously — for conventional lead-acid you should plan on using around 50 percent, so 2,400Wh. Lithium chemistries typically allow 80 percent or more
3. Allow for conversion losses of roughly 10 to 15 percent through the inverter
4. Divide usable watt-hours by your load. About 2,100Wh after losses, carrying 710W, gives roughly three hours

Want six hours instead of three? That is a bigger battery bank, not a bigger inverter. Nothing about the inverter changes.

If a quotation gives you an inverter size and no battery bank specification, it has told you half of what you are buying.

The appliance questions people actually ask

What size inverter do I need to run a refrigerator?

A fridge alone is modest — 100 to 200W running — but the compressor surge is the constraint. For a single domestic fridge plus lights, a 1 to 1.5 kVA unit with a genuine surge rating is sensible. Never put a fridge on an inverter that only just covers its running watts.

Note also that a fridge cycles. It does not draw continuously, which means over an evening it consumes much less energy than its running wattage suggests — good news for your battery bank, but no help at all with the surge.

What size inverter is needed to run a house?

It depends entirely on whether "the house" includes air conditioning and the pump. Lights, fans, fridge, TV and electronics for an average Ghanaian home sit at 1.5 to 3 kVA. Add an air conditioner or a pump and you are into 5 kVA and above, with a battery bank sized to match — which is the point at which solar charging usually starts paying for itself.

Can I run an air conditioner on an inverter?

Yes, if it is sized for it. An inverter-type AC is far kinder to a battery system than a conventional one because it modulates its compressor rather than slamming on and off. But a 1.5hp unit at around 1,200W will empty a modest battery bank quickly, so plan the bank, not just the inverter.

What about an electric iron, kettle or microwave?

These are pure resistive loads of 1,000W and up, and they will drain a domestic bank in minutes. They can be run on a large enough system, but in practice most households deliberately leave them off the inverter and wait for the mains. That is a sensible decision, not a compromise.

The Ghanaian conditions that change the arithmetic

Sizing guides written elsewhere assume a cool equipment room and a stable supply. Neither applies here.

• Heat derates everything. Inverters and batteries both lose capability as ambient temperature rises, and a sealed cupboard is the worst place for either. Ventilate the installation.
• Dust matters. Harmattan dust clogs cooling fans and heat sinks. An inverter that cannot shed heat throttles or shuts down.
• Humidity corrodes terminals. Battery terminals and lugs need checking and greasing, not just fitting.
• The supply sags while it is on. A 2024 Kleinman Center study of Accra found an average of about 219V against a 230V nominal, with voltage routinely more than 20 percent below nominal during peak evening hours. That is also the period when your inverter is trying to charge its bank, so charging is slower in the evening than the specification implies — one more reason solar charging is attractive, and one more reason a stabilizer upstream is worth having. Our voltage stabilizer guide covers that.

Five mistakes that cost the most

1. Sizing the inverter and ignoring the battery bank. The commonest error, and the one that produces a system that works for twenty minutes.
2. Ignoring surge ratings. Then blaming the inverter when the fridge trips it.
3. Mixing old and new batteries in one bank. The weakest battery sets the behaviour of the whole bank.
4. Buying far more inverter than the load needs. An oversized inverter has higher idle consumption, so it wastes energy every hour of every day doing nothing.
5. Installing it in a sealed cupboard. Guarantees heat, which guarantees early failure of both the electronics and the batteries.

Where this fits with your other options

If you are still deciding whether an inverter is the right answer at all, read inverter versus generator for a Ghanaian home first — the two solve different problems and many households end up with both.

If the equipment you are protecting is a server, a till or clinical equipment rather than household appliances, you want a UPS instead, and the sizing method differs. Start with how to choose a UPS in Ghana and then online versus line-interactive.

And if you want the batteries charged by the sun rather than by the mains, the architecture question comes first — see hybrid, off-grid or grid-tied.

Let us measure rather than estimate

We size inverters and battery banks for homes and businesses across Ghana, and we install what we supply. A survey takes the guesswork out: we measure your actual load, your actual surges and what your mains actually does, then specify both numbers against real readings.

Ask for a sizing survey, or see the inverters and batteries we carry.