How the calculator works
The calculator combines three live inputs (your state, system size, and quarterly bill) with four 2026 constants (STC zone rating, STC market price, years remaining in the scheme, and state-specific rebate amounts where applicable). It then estimates:
- Total rebate — federal STC + state bonus, applied at point of sale.
- Annual savings — based on offsetting 72% of your import bill plus a feed-in credit for excess generation.
- Out of pocket — system price minus rebates. (Average system price assumed at $1,100/kW installed; varies by installer.)
- Payback period — out-of-pocket divided by annual savings. Floor of 1.5 years for highly subsidised states.
- 25-year lifetime savings — annual savings × 25 minus the out-of-pocket cost. Panels are warranted for 25 years and typically still produce 80%+ of their original output at year 25.
- Cost of waiting — what the rebate step-down on 1 January will cost you if you delay.
What it doesn't capture
Three things move the real number versus the estimate:
Roof orientation and shading
North-facing panels produce about 100% of their rated output; east/west about 85%; south about 70%. Heavy shading from a single neighbouring tree can drop production by 20%. A specialist follow-up will assess this from a satellite image of your address.
Daytime usage pattern
Solar is worth more when you can use it during the day. A household that uses 8 kWh between 9am and 4pm offsets 8 kWh of imports (at 35c/kWh = $2.80/day). The same household that uses everything at 8pm only gets the feed-in tariff (4–10c/kWh = $0.32–$0.80/day). Pool pumps, ducted air-con, EV charging during the day, and electric hot water all push your numbers up.
Your specific retailer plan
Switching from a low feed-in plan (4c/kWh) to a competitive plan (10c/kWh) can be worth another $200–$500 per year on top of your savings estimate. We'll flag this when we get in touch if your current retailer is uncompetitive.
From estimate to actual quote
The calculator tells you whether solar is roughly worth it. The next step is the 30-second eligibility check, which gives you an exact rebate amount for your postcode plus a specialist follow-up within 24–48 hours for the full quote.
Common questions
How accurate is the solar savings calculator?
It's a believable estimate, accurate to within roughly 10% for a standard household. Real numbers depend on three things the calculator can't see: your specific roof orientation and shading, your daytime electricity usage pattern, and the exact retailer plan you're on. A specialist follow-up will give you exact numbers — that's the next step after the calculator.
What is STC zone and why does it matter?
Australia is split into four STC zones based on latitude and solar irradiance. Zone 1 is the most generous (NT, far north QLD/WA), Zone 4 is the lowest (Tasmania). Your state determines your zone, which determines your federal STC rebate. The calculator uses your state's STC zone rating to estimate your rebate.
What size system should I install?
Most Australian households install 6.6 kW — that's the size the calculator defaults to. If your quarterly bill is under $300, a 5 kW system is usually enough. If your bill is over $600 or you have a pool, EV, or are planning a battery, 8–10 kW makes more sense.
Does the calculator include the federal Cheaper Home Batteries rebate?
Not yet — the calculator focuses on solar PV at the moment. The federal battery rebate (~$372/kWh installed) and state battery programs are explained on our dedicated battery rebate page. Add a battery question to your call and your specialist will run the combined numbers.