Solar Battery Payback Calculator

This calculator works out how many years it takes a home solar battery to pay for itself in New Zealand, so you can judge whether adding storage to your solar system stacks up financially. Without a battery, any solar power you generate but do not use straight away gets exported to the grid at a low buy-back rate, then bought back in the evening at the much higher retail price. A battery closes that gap by storing your surplus solar for later use in your own home. You enter the installed cost of the battery, how many kilowatt-hours a year it lets you self-use instead of exporting, your retail power price per kWh, and the export buy-back rate per kWh. The calculator returns the battery payback period in years, the dollar saving per year, and the saving per kWh shifted from export to self-use. Use it to compare battery quotes against your own power and export rates, and to see how sensitive the payback is to those prices, since a bigger gap between what you pay and what you are paid for export means a faster payback. It is also worth weighing the payback period against the battery's warranty, typically around ten years, and remembering that backup power during an outage has value beyond the dollar saving. Figures are indicative estimates only, based on the rates and usage you enter.

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The saving is the gap between the power price and the export buy-back rate, on the energy the battery shifts to evening use. Compare the payback with the battery's warranty (often around 10 years). Backup power in outages is a benefit beyond the dollars. Estimate only.