Rates and assumptions last updated: 13 September 2026
Every number on this site that predicts savings is an estimate, not a forecast or a guarantee. Estimates are illustrative only, based on typical Melbourne conditions and the inputs shown with each figure. Your actual savings depend on your usage, your tariffs, your roof, weather, and how the system is used. This page lists the assumptions behind each calculator and example.
The visualiser converts your quarterly bill into an annual grid spend, then applies an assumed offset share of that spend.
The 25-year projection compounds these assumptions; small input changes compound into large differences over 25 years.
Used on: /
Example inputs: 34c/kWh usage tariff, 6c/kWh feed-in, 52–68% self-consumption, Melbourne irradiance. Ranges include federal STCs and the Victorian Solar Homes rebate only where eligible.
Used on: /solar-panels
Example inputs: 34c/kWh peak tariff, 6c/kWh feed-in, and the cycling figures shown beside each tier (an evening-load profile for a typical Melbourne household). Payback assumes the stated utilisation is achieved most days of the year.
Used on: /battery-storage
Example inputs: 18kWh/100km vehicle efficiency, 34c/kWh peak and 11c/kWh off-peak/solar tariffs. The ~4c/km figure assumes charging entirely from solar surplus, which depends on system size and driving patterns.
Used on: /ev-charging
Reverse-cycle figures assume a seasonal coefficient of performance (COP) commonly in the 3–5 range, varying with outdoor conditions and correct sizing. Gas comparison uses typical Victorian gas tariffs and an 85% seasonal gas appliance efficiency. Victorian Energy Upgrades incentives apply only where eligible under scheme criteria.
Used on: /heating-cooling
Heat-pump hot water figures assume a COP of 3.5–4.8 (typical range for quality units in Melbourne conditions), giving 60–75% less electricity than a conventional electric element, depending on ambient conditions, tank size and hot-water use. Example inputs: 34c/kWh tariff, standard off-peak rates where relevant. VEU and STC incentives apply only where eligible.
Used on: /hot-water
The numbers above are education tools. A real quote from us is prepared from an on-site or remote assessment of your property, your interval data where available, and your retailer's actual tariffs — and every design shows the modelled winter numbers before you commit.