A kilowatt (kW) is a rate. It tells you how fast something uses or makes power right now. A kilowatt hour (kWh) is an amount. It tells you how much energy got used or made over a period of time.
That one difference explains most of the confusion on a solar quote. Your system size is in kW. Your power bill is in kWh. They are not the same thing, and mixing them up is the reason people expect a 6.6 kW system to make 6.6 kWh a day. It does not. It makes about four times that.
The tap and the bucket
Picture a garden tap filling a bucket.
- kW is how fast the water comes out. Turn the tap on hard and you get a lot of litres per minute. That flow rate is your kW.
- kWh is how much water ends up in the bucket. That depends on the flow rate and how long you leave the tap running. Litres in the bucket is your kWh.
Same idea as a car. Speed is your kW. Distance travelled is your kWh. Driving at 100 km/h tells you nothing about how far you went. You also need to know how long you drove for.
So the sum is simple:
kW x hours = kWh
A 2 kW heater running for 3 hours uses 6 kWh. A 0.1 kW television running for 3 hours uses 0.3 kWh. Same three hours, very different buckets.
Watts and kilowatts
A watt (W) is the small version of a kilowatt. There are 1,000 watts in a kilowatt.
- 400 W = 0.4 kW
- 2,400 W = 2.4 kW
- 7,000 W = 7 kW
The Australian Government’s energy.gov.au points out that appliance input power is usually printed in watts on the packaging or the plate on the back, so you divide by 1,000 to get kilowatts.
Where the confusion costs Australians money
Here is where it actually matters, one decision at a time.
1. Your bill charges you in kWh
Pull out your last electricity bill. The usage rate is written in cents per kWh. The retailer does not care how fast you used power. They care how much you used.
Your feed in tariff is also in cents per kWh. Every kWh you send to the grid earns that rate. We cover how those rates work in our guide to solar feed in tariffs in Australia.
So when you want to know what solar saves you, the number you need is kWh, not kW.
2. Your panels are rated in watts
A quote might say “15 x 440 W panels”. That 440 W is a rate, measured under standard lab test conditions. It is the most that panel can push out at one moment on a perfect day.
Add them up and you get the system size: 15 x 440 W = 6,600 W = 6.6 kW.
3. A 6.6 kW system does not make 6.6 kWh a day
This is the big one. 6.6 kW is the peak rate on a clear day at midday with the sun straight on. It is not a daily total.
Across a full year, output per kW installed varies by city and roof. Design figures from the Clean Energy Council guidelines, published in this SolarQuotes reference table, put Sydney at roughly 3.9 kWh per day for every 1 kW installed, averaged over the year.
On that figure, a 6.6 kW system in Sydney averages about 26 kWh a day. Not 6.6 kWh. Northern cities do better, and Hobart and Melbourne do a bit worse. Shade, roof direction, roof pitch and dirty panels all pull the number down.
Winter days sit well under that average and summer days well over it. If an installer quotes you a daily production number, ask whether it is an annual average or a best case summer day.
4. Your inverter is rated in kW
The inverter turns DC from the panels into AC for your house. Its rating is a rate: the most AC power it can push out at any moment.
This is why quotes often pair a 6.6 kW panel array with a 5 kW inverter. Panels rarely hit their full lab rating in real conditions, so a slightly smaller inverter is normal and is allowed by the rebate rules up to a limit. It is not the installer cutting corners.
It also matters for your grid connection. In South East Queensland, for example, Energex and Ergon Energy allow a standard single phase home to export up to 5 kW, while permitting larger inverter capacity that gets limited in software. That 5 kW export cap is a rate. It does not cap how many kWh you can send over a day.
5. Your battery has both numbers, and both matter
A battery is the place people get hurt most, because a battery is sold with two numbers that sound similar.
- Capacity, in kWh. How much energy the battery holds. Think bucket size.
- Power output, in kW. How fast it can pour that energy out. Think tap size.
A 10 kWh battery with 5 kW output holds 10 kWh and can supply at most 5 kW at any instant. Run it flat out at 5 kW and it empties in about 2 hours. Run it gently at 1 kW and it lasts about 10 hours.
Now think about a blackout. Your battery is full at 10 kWh, and the oven (2.4 kW), the kettle (2.4 kW) and a split system (1.5 kW) all come on together. That is 6.3 kW of demand against a 5 kW tap. The battery cannot keep up, even though it is completely full. Something trips or drops out.
So a big kWh number alone does not mean your house runs normally in a blackout. You need enough kW for what is switched on at once, and enough kWh to last the hours you need. The battery also has to be wired for backup with the right switchgear, which not every install includes by default.
Ask any battery salesperson these three questions:
- What is the continuous kW output, not just the peak surge kW?
- Which circuits stay on in a blackout, and which do not?
- What is the usable kWh, not the total kWh?
Our guide to solar battery costs in Australia goes deeper on pricing, and the federal Cheaper Home Batteries Program has reduced upfront costs since July 2025.
kW vs kVA on an inverter spec sheet
Read an inverter datasheet or a grid connection form and you will hit kVA. Kilovolt amps.
Here is the plain version.
- kW is real power. The part that does actual work, like heating your kettle.
- kVA is apparent power. The total the equipment and the wires have to carry.
- kW = kVA x power factor. Power factor is a number between 0 and 1.
If power factor is 1.0, kW and kVA are the same number. Most home solar inverters run at or near 1.0 by default, which is why a “5 kVA” inverter is usually sold as a “5 kW” inverter and nobody blinks.
The paperwork insists on kVA because inverters can be told to supply reactive power to help hold the local voltage steady. Under AS/NZS 4777.2, the inverter standard administered through AEMO’s distributed energy program, inverters can be required to run at power factors below 1.0 when the network asks. Then kW and kVA stop matching, so network rules are written in kVA.
For a homeowner, treat kVA and kW on a home solar inverter as roughly the same size number. Just do not be surprised when your connection approval talks in kVA and your quote talks in kW.
Common appliances: kW draw and kWh used
This table shows the difference in one glance. The middle column is the rate. The right column is the amount.
| Appliance | Typical power draw (kW) | Typical run | Energy used (kWh) |
|---|---|---|---|
| LED light globe | 0.01 | 5 hours | 0.05 |
| Laptop | 0.05 | 5 hours | 0.25 |
| 55 inch TV | 0.1 | 4 hours | 0.4 |
| Fridge (averaged over a day) | 0.05 to 0.1 | all day | 1 to 2 |
| Washing machine (cold wash) | 0.3 | 1 hour cycle | 0.3 |
| Pool pump | 1.0 | 6 hours | 6 |
| Dishwasher (hot cycle) | 1.2 | 1.5 hours | 1.8 |
| Split system, cooling a living room | 1.0 to 2.0 | 5 hours | 5 to 10 |
| Electric oven | 2.4 | 1 hour | 2.4 |
| Electric kettle | 2.4 | 3 minutes | 0.12 |
| Vented clothes dryer | 2.4 | 1 hour | 2.4 |
| Electric hot water element | 3.6 | 3 hours | 10.8 |
| Home EV charger (single phase) | 7.0 | 4 hours | 28 |
These are typical ranges, not your numbers. Check the label or plate on your own appliance for its watts, then divide by 1,000. The Australian Government’s Energy Rating Calculator can help with running costs for common appliance types.
Now compare the kettle and the pool pump. The kettle draws 2.4 kW, more than twice the pump, yet it uses 0.12 kWh against the pump’s 6 kWh. The kettle is a big tap open for seconds. The pump is a small tap open for hours.
That is the lesson. The appliances that wreck your bill are the boring ones that run for hours: pool pumps, hot water, heating and cooling, and now EV charging. A quick blast of kW barely registers. Steady hours of kWh is what you pay for. It is also why load shifting works with solar. Move the pool pump, the dishwasher and the hot water into the middle of the day and those kWh come from your roof instead of your retailer.
Decoding every unit on your solar quote
Here is what each line actually means.
| What the quote says | Unit | What it is telling you |
|---|---|---|
| 15 x 440 W panels | Watts | The rate one panel makes at peak, in lab test conditions |
| 6.6 kW system | Kilowatts | All the panels added together. A rate, not a daily total |
| 5 kW inverter | Kilowatts | The most AC power the inverter can deliver at one moment |
| 5 kVA inverter | Kilovolt amps | The same rating expressed as apparent power, used in grid paperwork |
| Estimated output 26 kWh/day | Kilowatt hours | Energy produced per day, usually an annual average |
| Estimated 9,500 kWh/year | Kilowatt hours | The annual total. Compare this against your bill |
| 5 kW export limit | Kilowatts | The most you may push to the grid at any instant |
| 10 kWh battery | Kilowatt hours | How much energy the battery stores |
| 5 kW battery output | Kilowatts | How fast the battery can supply the house |
| Usage rate, c/kWh | Cents per kilowatt hour | What you pay for each unit you draw from the grid |
| Feed in tariff, c/kWh | Cents per kilowatt hour | What you are paid for each unit you export |
If two quotes show different daily kWh estimates for the same kW system size, that is worth a question. One of them has made different assumptions about shade, roof direction or losses. Our guide on how to compare solar quotes walks through what else to check line by line.
The three sums worth knowing
1. Watts to kilowatts. Divide by 1,000. A 2,400 W kettle is 2.4 kW.
2. Power to energy. Multiply kW by hours. A 1 kW pool pump for 6 hours is 6 kWh.
3. Energy to dollars. Multiply kWh by your usage rate from your bill. If the rate is in cents, divide by 100 first. That 6 kWh pool pump at a rate of 30c per kWh costs $1.80 a day.
The third sum turns a quote into a real decision. Compare the annual kWh on your bill against the estimated annual kWh on the quote, then work out how much of it you will use at home rather than export. Our guide on how many solar panels you need covers the sizing side, and you can browse our free directory of Australian solar companies to line up a few quotes.
Frequently asked questions
Is kW or kWh bigger?
Neither. They measure different things, so they cannot be compared directly. It is like asking whether kilometres per hour is bigger than kilometres. kW is a speed. kWh is a distance.
How many kWh does a 6.6 kW solar system produce in a day?
Far more than 6.6. Using Clean Energy Council design figures of about 3.9 kWh per day per kW installed in Sydney, a 6.6 kW system averages roughly 26 kWh a day across the year. Sunnier cities do better and Hobart and Melbourne do a bit worse. Shade, roof direction and roof pitch change it for every individual home, so treat any figure on a quote as an estimate.
Why is my battery sold with a kWh number and a kW number?
Because they answer different questions. The kWh tells you how much energy it stores, so how long it can run your house. The kW tells you how fast it can supply energy, so how much you can have switched on at once. A battery can be full and still fail to run your oven if the kW output is too low.
What is the difference between kW and kVA?
kW is real power, the part doing useful work. kVA is apparent power, the total the wiring and equipment must carry. kW equals kVA multiplied by the power factor. Home solar inverters usually run at a power factor near 1.0, so the two numbers are near enough the same. Network connection paperwork uses kVA because inverters can be asked to supply reactive power, which makes the two numbers separate.
Does a bigger kW system always save more money?
Not automatically. A bigger system makes more kWh, but your saving depends on how many of those kWh you use yourself instead of exporting. Self consumed energy saves you your full usage rate. Exported energy only earns your feed in tariff, which is usually much lower. That is why matching the system to your daily habits matters more than chasing the biggest kW number.
How do I work out what an appliance costs to run?
Find the watts on the appliance label and divide by 1,000 to get kW. Multiply by the hours you run it to get kWh. Multiply that by your usage rate from your bill. A 3.6 kW hot water element running 3 hours a night is 10.8 kWh, which at 30c per kWh is $3.24 a day.
Related reading
- what size solar system you need
- the average Australian electricity bill
- peak and off-peak electricity times
About this research
This is independent desk research by Solar Cobber. We did not visit sites, request quotes or accept payment for inclusion. Figures are dated and sourced, and pricing and policy details change, so confirm current terms directly before you sign anything.