Solar & Battery Payback

Payback, NPV and IRR for a rooftop solar system, with or without a battery, over its whole life. Australian defaults; every figure editable.

Array

System size

Installed cost

After any up-front rebate, so what you actually hand over.

Specific yield

kWh/kW/yr

Around 1400 for the southern Australian capitals; more further north.

Used on site as generated 30 %

The rest is exported for the feed-in credit.

Panel degradation

%/yr

cents per kWh

Import rate

Feed-in tariff

Bill inflation

%/yr

Applied to the import rate only. Feed-in rates have not tracked retail prices.

Currency symbol

Add a battery

Stores what you would otherwise export, to use at the import rate instead.

Discount rate

%/yr

What the same money would earn elsewhere.

Analysis horizon

years

This system pays for itself in

— years

present value vs year

Starts at the outlay and climbs as each year's saving is discounted back to today. Where it crosses the break-even line is the discounted payback.

kWh