4–10¢
a typical feed-in tariff — what you're paid to export a kWh
Slide to the size you're weighing up and watch, on a real day for your postcode, how much of that solar your home would actually use — and how much more you'd keep by pointing your big loads at the sun. No recommendation, no sign-up: the data's here, you decide.
Solar generation from Bureau of Meteorology satellite data for your postcode; heating and cooling from BoM temperatures scaled to your home's efficiency; usage from the loads you pick and, if you like, calibrated to your own bill. Move the size and everything updates live.
This is a typical Australian household day — a guide, not a reading of your exact home. To turn your loads into an hour-by-hour shape, the tool assumes:
That’s why the two big draws sit outside solar hours — morning and night. Your own timing will differ, so these are indicative; add a recent bill above to calibrate the totals to your home. And these morning-and-night loads are exactly the ones you could move into the middle of the day — switch to “Surplus used” to see how much your solar could cover.
This tool estimates your system size and how much of your solar you’ll use — not full system design. For inverter choice, roof layout and panel placement, talk to your installer or a tool like SunSPOT.
What the graph shows. An average day for your postcode — the mean across clear and cloudy days — because that's the honest basis for sizing and for your yearly figures. The Clear toggle is for information only: a bright day makes more solar but you use a smaller share of it. Day length and sun position shift with your latitude, in both summer and winter.
When loads run (typical patterns). Aircon: afternoon into evening, off overnight. Heating: morning and evening. EV: overnight, unless you move it into the daytime. Hot water & pool: overnight on a timer, or shifted into the sun. Your own timing may differ — so we calibrate the daily and yearly totals to your bill rather than relying on the exact hours.
The basics. Panel counts assume 440 W panels. Figures are estimates (usually within ~15–20%) to help you make decisions — not a quote or a guarantee of savings. Your roof, shading, tariff and habits all move the real number, so confirm the right system with a CEC-accredited installer before you buy.
A branded, one-page summary of the size you've landed on and these numbers — plus the questions to put to any installer. Take it along and quote against it.
Most tools stop at kilowatts. This one carries on to the number that decides whether the system was worth it — how much of what you generate you actually use, and what that’s worth over a year.
Three things, not one. The size that suits your household. The shape of your solar day — how much of it lands while the house is empty. And the surplus you’d keep if the big loads ran at midday instead of after dark. Flip the Surplus used toggle above to see that third one.
Where the savings figure comes from, in full. It is the extra power you’d use yourself by shifting those loads, multiplied by about 25c a kilowatt-hour — the gap between roughly 30c to buy a unit and roughly 5c to export it. Nothing is hidden in that sum, and you can check it against your own bill.
What it deliberately doesn’t do. It won’t give you a dollar figure to the decimal, and it won’t price a battery. Your own two rates — what you pay at the evening peak, and what you’re paid to export — move that number more than anything else on this page. On a high peak rate the saving is larger; on a flat tariff with a generous feed-in, smaller.
Getting the size right matters — but even a perfectly-sized system sends most of its power to the grid for cents, because it's made at noon while your home draws power morning and night. A kilowatt-hour of your own solar, used at home, is worth several times more than one exported.
So the real question isn't only what size — it's how much of it you keep. That's what Powermind is built to do: shift your hot water, car and aircon onto your surplus, automatically.
The sizing above, and the case for using your solar rather than exporting it, both rest on Australian energy research. A few of the voices behind it:
“More than half of Australian homes have an electric water heater with a storage tank — a thermal battery that often stores more energy than a home battery.”
University of New South Wales — Hot water heaters & daytime solar, 2024
“Close to 50% of water heating was successfully shifted from night to day. Most householders reported no noticeable change to their hot water service — only 0.3% of households opted out.”
UNSW SolarShift trial, 18,000 South Australian households (Yildiz & Saberi) — funded by ARENA & RACE for 2030
“Before spending $10,000+ on a battery, consider whether you can shift existing loads to solar hours. Shifting 5–10 kWh of daily load into solar hours effectively eliminates curtailment for most 6.6 kW systems — and costs nothing.”
Gridly — Australian solar export economics, 2026