It's the first question nearly everyone asks, and the honest answer is that panel count is the wrong unit. What matters is system size in kilowatts, and that comes from four things: how much power you use, when you use it, what your roof can physically take, and whether storage is part of the plan.
Start with your bill, not a rule of thumb
Find the daily average usage in kilowatt-hours on your electricity bill — most retailers print it. A typical Newcastle household sits somewhere between 15 and 30 kWh a day, but the spread is wide, and heat pumps, pools, ducted air conditioning and an EV all move it sharply.
A rough starting point: a well-oriented system in Newcastle produces around four kilowatt-hours per day for every kilowatt installed, averaged across the year. Less in a wet July, more in January. Work back from your usage and you have a first estimate.
When you use it matters as much as how much
A household that's out all day and heaviest at 6pm gets far less from a big array than the numbers suggest, because most of that generation gets exported for very little. Either shift some load into daylight, or plan for a battery — that's the choice, and it changes the sensible size.
What the roof will actually take
Every panel needs unshaded north, east or west-facing space, with clearances from ridges, edges, vents and whirlybirds. Older Newcastle tile roofs, dormers, skylights and heritage constraints all cut into the usable area, and a full south-facing pitch is rarely worth the money.
This is why we measure rather than quote from a satellite image alone. The jobs on our projects pages show what real Newcastle roofs fit — a Colorbond roof in Mayfield takes a very different layout to a tiled cottage in Merewether.
Leave room for what's coming
- An EV adds meaningfully to daily usage — plan for it before the car arrives, not after.
- A hot water heat pump shifts your heating load onto electricity you can generate.
- A battery changes the maths entirely: surplus that used to be exported for cents becomes evening power you'd otherwise buy at peak rates.
- Inverter capacity, network export limits and switchboard headroom all constrain later expansion — better to allow for it now.
Worked examples
A couple working from home with gas cooking and no pool will typically be well served by a modest system sized close to their daytime usage. A family of four with ducted air conditioning, a pool pump and an EV needs something substantially larger, and usually a battery, because their evening peak is where the money goes.
Get a number for your house
Our estimator does this properly — it takes your usage, your roof type, whether you already have solar and whether an EV is in the picture, and returns a system size and a real price with the rebates applied. It's the fastest way to turn a general question into a specific answer.
Want this applied to your house?
Our estimator gives you an indicative system size and savings figure in a couple of minutes — then we confirm it against your actual bills.
Get your estimate