The formula
Net system cost ÷ annual savings
At its simplest, payback period is: (upfront system cost − STC rebate) ÷ (annual electricity bill savings). The result is a number of years. Every input in that formula is specific to your property — which is why a generic "solar pays for itself in X years" figure, without your numbers behind it, isn't something we'll put on this page.
Step by step
What goes into each side of the equation
1. Net system cost
The upfront price of your system, minus the STC rebate your installer applies at the time of purchase. Sydney is rated Zone 3 (zone factor 1.382) for STC purposes — see our solar page for how that rebate works.
2. Annual generation
How much electricity your system actually produces in a year, which depends on system size, roof orientation and shading — not just the panel's rated wattage.
3. Self-consumption vs export
Electricity you use as it's generated saves you the full retail rate. Electricity you export earns a much lower feed-in tariff. A system and usage pattern with higher self-consumption pays back faster than one that exports most of its output.
4. Your usage pattern
A household home during the day (or with a battery storing daytime solar for evening use) converts more generation into savings than a household that's mostly out during daylight hours.
Why we don't publish a generic number
A property-specific figure, not a marketing average
Two identical solar systems on two different roofs, with two different usage patterns, can have meaningfully different payback periods. A single headline number ("solar pays for itself in 4 years!") averages over all of that — which makes it easy to overstate for a specific property. We calculate payback from your actual roof, usage and system design during your assessment, rather than publishing an indicative range that may not match your situation.
Also worth reading
The federal battery rebate, explained and what size battery do I need? — if you're weighing solar alongside a battery.