Enter your power bill and roof details to find out how many solar panels you need, your expected annual savings, and when your system pays for itself.
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Enter your monthly power bill, location, and roof direction to get a system size estimate and payback calculation.
Check a recent power bill or use your average across seasons.
More peak sun hours = more power generated per kW of installed panels.
| Region | Peak sun hours/day | kWh/kWp per year |
|---|---|---|
| Nelson / Marlborough (NZ) | 5.0 | 1,460 |
| Canterbury / Christchurch (NZ) | 4.5 | 1,314 |
| Auckland (NZ) | 4.2 | 1,226 |
| Wellington (NZ) | 3.8 | 1,109 |
| Perth (AU) | 5.8 | 1,693 |
| Brisbane (AU) | 5.5 | 1,606 |
| Adelaide (AU) | 5.3 | 1,547 |
| Sydney (AU) | 4.7 | 1,372 |
| Melbourne (AU) | 4.2 | 1,226 |
Figures assume north-facing panels at optimal tilt angle and 80% system efficiency.
A typical home spending $200/month on power needs a 6–8 kW system (15–20 panels) in Auckland to cover about 80% of consumption. Use the calculator above for a personalised estimate.
Typically 8–14 years depending on location, bill size, and install cost. After payback, you generate essentially free electricity for another 10–15 years. Nelson and Canterbury typically pay back faster due to higher sun hours.
A battery increases self-consumption from ~35% to ~75%, reducing grid imports. However, the $8,000–$15,000 battery cost typically extends the total system payback period. Whether it makes sense depends on your usage pattern and export rate.
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