"How many panels do I need?" is usually the first question on the phone, and the honest answer is that the number of panels is the last thing we work out, not the first. Panel count falls out of two other numbers: how much electricity you use, and how much a kilowatt of panels produces on your roof.
Short answer: divide your average daily electricity use (in kWh) by how much one kilowatt of panels produces per day where you live, and that gives you a starting system size in kW. Divide that by the wattage of one panel and you have your panel count. On the Sunshine Coast, most homes end up somewhere in the 6–10 kW range, which with 440-watt panels is roughly 14 to 23 panels. Roof space, shading, your plans for a battery or EV, and network export rules then push that number up or down.
Here's the method step by step, so you can sanity-check any quote you're given.
How many solar panels does your home need? The three-step method
You need three numbers:
- Your average daily usage in kWh. From your power bill.
- How much 1 kW of panels produces per day on the Sunshine Coast.
- The wattage of the panel being quoted. From the datasheet.
Then:
- Daily kWh ÷ daily output per kW = system size in kW
- System size in watts ÷ panel wattage = number of panels
That's the whole calculation. The skill is in choosing sensible inputs, so let's go through each one.
Step 1: find your daily usage from your power bill
Your bill shows total kWh used over the billing period, and usually the number of days. Divide one by the other.
If your bill shows 1,800 kWh over a 90-day quarter, that's 20 kWh a day. Better still, look at a full year of bills, because summer air conditioning and winter heating swing usage a lot. Your retailer can also give you interval data, which shows usage by time of day; that matters later if you're thinking about a battery.
If you already have solar, your bill only shows what you imported from the grid, not what you used. In that case your monitoring app or inverter will show total consumption, or we can estimate it from generation and export figures.
Two adjustments worth making up front:
- Planned changes. An EV, a pool, a heat pump hot water system, ducted air, a granny flat or a home office all add load. Size for the house you'll have in a few years, not the one you have today.
- Electrification. If you're planning to swap gas cooking or gas hot water to electric, that usage moves onto your power bill.
Step 2: how much does 1 kW of panels produce on the Sunshine Coast?
This is where most online solar calculators go wrong, so it's worth a moment.
Our location pages quote around 7.5 hours of peak sunlight a day for the Sunshine Coast. That's a measure of the sunshine resource. It isn't what comes out of your inverter, because real systems lose output to panel heat, orientation, roof pitch, shading, dust, wiring and inverter conversion. Multiply 1 kW by 7.5 hours and you'll overestimate what lands in your meter.
For sizing, we use more conservative output figures. Our planning numbers for the Sunshine Coast are:
| System size | Typical daily output (annual average) | Best suited to |
|---|---|---|
| 5 kW | ~20 kWh | Units, townhouses and low-usage couples |
| 6.6 kW | ~26 kWh | The standard Sunshine Coast family home |
| 10 kW | ~40 kWh | Larger homes, pools, ducted air conditioning |
| 13 kW+ | ~52 kWh | High-usage homes, or homes adding a battery or EV |
Those work out to roughly 4 kWh per kW of panels per day, averaged across the year. Summer days will beat it, short winter days won't reach it, and a north-facing unshaded roof will do better than a shaded east-west split. Your actual number depends on your roof, which is why we measure it on a site visit rather than guessing.
Step 3: solar panel sizes and wattage
Panels are rated in watts, and the rating varies by model, so always check the datasheet for the exact panel on your quote. As an example, one common Jinko residential series, the Tiger Neo 54-cell panel, is listed on its datasheet at 425 to 445 watts depending on the exact model.
Higher wattage per panel means fewer panels for the same system size, which matters on a small or awkward roof. It doesn't mean a better panel on its own; efficiency, warranty terms, and the manufacturer's track record in Australia matter more than a few extra watts.
Note that "system size" in Australia almost always means the total panel wattage, not the inverter size. A "6.6 kW system" is typically 6.6 kW of panels on a smaller inverter. Sizing panels a little above the inverter is normal practice and the allowable ratio is set by accreditation rules.
Solar power calculator: a worked example
This is illustrative arithmetic, not a quote. It uses our planning figure of about 4 kWh per kW per day and a 440 W panel, and rounds to whole panels.
| Average daily usage | System size to match daily use | Panels at 440 W |
|---|---|---|
| 15 kWh | ~3.8 kW | ~9 |
| 20 kWh | ~5 kW | ~12 |
| 25 kWh | ~6.3 kW | ~15 |
| 30 kWh | ~7.5 kW | ~17 |
| 40 kWh | ~10 kW | ~23 |
So a household using 20 kWh a day would need about 5 kW of panels to generate, on average across the year, roughly what it uses. That's 5,000 W ÷ 440 W ≈ 11.4, rounded up to 12 panels.
Why matching daily usage is only the starting point
Here's the catch. A system that generates as much as you use in a day still won't cover your evening usage, because the panels aren't producing then. A typical Sunshine Coast home only self-consumes 30–50% of its solar; the rest is exported for a few cents per kWh and bought back at night for much more.
That changes the sizing logic depending on what you're after:
- Solar only, keep it lean: sizing close to daytime usage, plus a margin for winter, gives the best return per dollar. Oversizing mainly increases exports, which pay very little.
- Solar with a battery now or later: size bigger. The array has to cover your daytime usage and fill the battery for the evening. A big battery on a small array sits half-empty, especially in winter. We cover the trade-off in more solar panels or a bigger battery.
- EV on the horizon: size bigger again, and think about daytime charging.
That's why a household using 20 kWh a day often ends up with 6.6 kW rather than 5 kW, and why households planning a battery frequently go to 10 kW.
What limits how many panels you can fit?
Even with the arithmetic done, a few practical limits decide the final number.
Roof space and orientation. North-facing roof space is the most productive across the year. East and west roofs work well too and spread generation across the morning and afternoon. South-facing roof space is usually a poor return. Vents, skylights, hips and valleys all eat into usable area.
Shading. Trees, neighbouring buildings, chimneys and even a satellite dish. Shade in winter, when the sun is lower, catches people out.
Your inverter and phase supply. Single-phase homes have tighter limits on inverter size and how much they can export than three-phase homes. If you're on the edge, our explainer on single vs three-phase solar is worth a read.
Network export rules. Energex sets what your address is allowed to export, and a bigger array may need export limiting. We don't guess these numbers; they're confirmed when the connection application is lodged.
Budget. On the Sunshine Coast, as at August 2026, a 6.6 kW system typically lands between $5,000 and $7,000 installed with the STC discount applied, and a 10 kW system between $8,000 and $11,000. For what moves a job up or down those bands, see our guide to solar panel cost on the Sunshine Coast.
Is 10kW solar enough to run a house?
On paper, for most Sunshine Coast homes, yes. Using our planning figure, a 10 kW system averages around 40 kWh a day across the year, which is more than many family homes use.
In practice, "run a house" needs unpacking:
- During the day: a 10 kW system will cover the daytime load of most homes on a decent day, with plenty left to export.
- At night: no solar system runs a house at night on its own. Without a battery, everything after sunset comes from the grid.
- In a blackout: a standard grid-connected system shuts down when the grid does, for line-worker safety, so solar alone won't keep your lights on in an outage either.
- In winter or a run of cloudy days: output drops well below the annual average.
So 10 kW is a generous size for most homes, and it's the size that makes the most sense if a battery is part of the plan, because it leaves real surplus to fill one. If you're deciding between 10 kW and something bigger, our comparison of 10kW vs 15kW solar systems goes through who genuinely needs the larger array.
Common sizing mistakes we see on quotes
- Sizing off a single bill. One quarter is a snapshot. Summer and winter can differ a lot.
- Ignoring evening usage. A system sized to "cover your bill" on paper won't, if most of your use is after dark.
- Overselling the array for exports. Feed-in tariffs are low. Extra panels you can't use and can't store mostly earn small change.
- Undersizing when a battery is planned. Adding panels later costs more than doing it once, and may need a different inverter.
- Panel count as a selling point. "26 panels!" means nothing without the wattage. Compare total kW, panel brand and warranties, not the count.
How we size systems
On a site visit we look at twelve months of usage where available, measure the roof, check shading across the year, look at your switchboard and phase supply, and ask what's changing in the next few years. Then we recommend a size, and explain why, rather than leading with a package. Our residential solar panels page shows the system ranges we install most often, from 3–5 kW starter systems through to 10–15 kW for larger homes.
Frequently asked questions
How many solar panels does your home need?
Divide your average daily usage in kWh by about 4 kWh (a planning figure for what each kW of panels produces per day on the Sunshine Coast, averaged across the year) to get a system size in kW, then divide by the panel wattage. A household using 20 kWh a day needs roughly 5 kW, or about 12 panels at 440 W. Most Sunshine Coast homes end up between 6 and 10 kW once evening use, batteries and future plans are factored in.
Is 10kW solar enough to run a house?
For most homes, a 10 kW system produces more energy across a day than the house uses, around 40 kWh a day on average using our planning figure. But it can't run the house at night or in a blackout without a battery, and winter output is lower. It's a good size for larger homes and for anyone planning to add battery storage.
How many solar panels do I need for a 6.6kW system?
With panels in the 425–445 W range, a 6.6 kW system is about 15 or 16 panels. With lower-wattage panels it's more. Always compare the total system size in kW and the panel wattage, not just the number of panels.
How much does a 6.6kW solar system produce per day?
Our planning figure for the Sunshine Coast is around 26 kWh a day averaged across the year. Summer days will typically produce more and winter days less, and your actual output depends on orientation, roof pitch and shading.
Should I get more panels than I need?
A modest margin is sensible, especially if a battery, EV or pool is likely. Going far beyond your usage mostly increases exports, which earn only a few cents per kWh, so the extra panels pay back slowly unless you can store or use the power.
