Free Australian energy calculators
Fast, unbiased tools for the energy and sustainability decisions Australian households actually face — built on real 2025–26 numbers, not product sales. No sign-up, no email capture, no fluff.
Work out whether rooftop solar will pay back on your roof, or compare the 10-year cost of an electric vehicle versus an equivalent petrol car. Every Wattcalc calculator runs in your browser with no account required.
Solar Payback Calculator
Estimate the payback period and lifetime savings of a rooftop solar system using your system size, daily usage, feed-in tariff and electricity rate.
Calculate solar payback →EV vs Petrol Calculator
Compare the 5- or 10-year total cost of ownership for an electric vehicle versus a petrol car — fuel, servicing, and the year EV becomes cheaper overall.
Compare EV vs petrol →Why Wattcalc
Wattcalc is built for Australians making real decisions on solar, batteries, EVs and electricity bills. Every calculator uses current Australian inputs — average retail tariffs, residential feed-in rates, ATO logbook conventions for vehicle running costs, and ARENA-published assumptions for solar system performance.
We are not solar installers, EV dealers or electricity retailers. We don't sell leads. The numbers you see are not influenced by who pays us — see our disclaimer for the full position.
Common questions Wattcalc answers
- Will solar pay back on my house? Use the solar payback calculator to model your system size, daily usage and self-consumption against current Australian feed-in tariffs.
- Is an EV actually cheaper than a petrol car? The EV vs petrol calculator compares total cost of ownership across fuel, electricity and servicing over 5 or 10 years and shows the break-even year.
- How do I cut my electricity bill in 2025–26? Read our guide to reducing your electricity bill for the highest-impact changes Australian households can make.
- Is solar still worth it in 2026 with low feed-in tariffs? See Is solar worth it in Australia in 2026? for a current view of the maths and the role of self-consumption.
Latest from the Wattcalc blog
Is solar worth it in Australia in 2026?
How feed-in tariffs, retail electricity rates and self-consumption shape the payback maths in 2026 — with worked examples for a typical 6.6kW system.
Read article →EV vs petrol car Australia: the real cost breakdown
The real running, fuel and servicing costs of an EV versus a petrol car in Australia — using current pump prices and home electricity rates.
Read article →How to reduce your electricity bill (2025–26)
The highest-impact, lowest-effort ways to cut a typical Australian electricity bill — from tariff swaps to smart appliance scheduling.
Read article →