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, model the maths on a home battery with the May 2026 federal rebate, see how much a heat pump hot water system saves, compare the 10-year cost of an EV versus a petrol car, or estimate the cost of installing a home EV charger. Every Wattcalc calculator runs in your browser with no account required.
Solar Payback Calculator
Estimate the payback period and 25-year lifetime savings of a rooftop solar system using your system size, usage, feed-in tariff and retail rate.
Calculate solar payback →Home Battery Payback Calculator
Model the financials of a home battery in 2026, with the federal Cheaper Home Batteries rebate built in. See payback period and 15-year net benefit.
Run battery payback →Heat Pump Hot Water Calculator
Compare running cost of a heat pump vs gas, electric or off-peak. Includes STCs and state rebates (Victorian VEU, NSW ESS) for accurate net cost.
Run heat pump payback →EV vs Petrol Calculator
Compare 5- or 10-year total cost of ownership for an EV versus a petrol car — fuel, electricity, servicing, and the year EV becomes cheaper overall.
Compare EV vs petrol →EV Home Charger Cost Calculator
Cost an EV home charger install — single vs three-phase, simple vs complex job — and compare 5-year running cost: off-peak, solar, public DC.
Cost an EV charger →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.
- Should I add a battery? Run the home battery payback calculator with the May 2026 federal Cheaper Home Batteries rebate netted off automatically.
- Is a heat pump cheaper than my gas hot water? The heat pump hot water calculator compares running cost and stacks STCs with state rebates.
- Is an EV actually cheaper than a petrol car? The EV vs petrol calculator compares total cost of ownership over 5 or 10 years and shows the break-even year.
- What does a home EV charger cost to install? Use the EV charger cost calculator for install bands, hardware costs and 5-year running cost vs public DC.
- 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.
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 →