Calculators
How many years until solar pays back?
Adjust consumption, system size, price and subsidy. The calculator estimates generation, savings and payback including panel degradation and price growth.
Common questions
How much does a home solar system generate?
The calculator starts from 1000 kWh per installed kWp a year. Your installer's quote should give an expected yield for your roof and region, so enter that. In New Zealand north-facing panels generate the most; east- and west-facing panels produce a little less, and south-facing or shaded panels noticeably less.
What is a typical payback?
EECA says 7 to 10 years if your household uses most of the electricity it generates, and longer in some situations. Put your own quote and usage into the calculator to check.
What is self-consumption and why does it matter?
The share of your solar output you use yourself. Each unit you use saves the full price you pay per kWh, while exports earn only the buy-back rate, which each power company sets. Running the dishwasher, hot water cylinder or an EV charger in the middle of the day raises it.
Is a time-of-use plan worth it with solar?
Often, if you can use power during the day and keep usage down in the evening peak. Since July 2026 large power companies also have to offer plans that pay more for exports at peak times, so compare the buy-back rates as well.