Solar Payback Calculator Australia

Estimate the annual savings and simple payback period for an Australian rooftop-solar quote. The result compares self-consumed solar and exported energy using your quote, generation estimate and electricity rates.

Your home and generation estimate

Compare a new rooftop solar system with keeping a home without solar. For a battery bundle, ask for a separate solar-only quote. Existing solar upgrades and battery savings need a separate model.

Household electricity use (kWh/year)

Add up 12 months of electricity use from your bills.

Panel capacity (kW)

Use the total panel capacity, not the inverter rating.

Estimated solar generation (kWh/year)

Use the installer’s site-specific AC estimate after shading, system losses and export curtailment. No location or weather estimate is supplied here.

Solar used directly at home (%)

Share of solar generation used while it is generated, not the share of household usage covered. Use interval data or an installer estimate; annual usage alone cannot establish this.

Your electricity rates

Avoided electricity rate ($/kWh)

Enter 0.30 for 30 cents. For time-of-use plans, use the weighted rate for the imports solar would replace.

Solar feed-in rate ($/kWh)

Use your confirmed export rate, or zero for no credit. Assumes a flat, non-negative rate for all exported energy; export fees and tiered tariffs are not modelled.

The installed quote

Installed solar quote ($)

Include GST, installation, electrical work, metering and other quoted costs.

Confirmed rebate or discount ($)

Leave at zero if already deducted from the quote. Enter confirmed amounts only; eligibility is not calculated.

Annual maintenance allowance ($)

Optional annual allowance; zero excludes maintenance. Inverter replacement is not included.

Your quote check

Enter your quote, energy estimates and rates to see the payback.

Before accepting a quote

Ask how roof orientation, shading and system losses affect the generation estimate.
Check panel and inverter models, warranties, installer credentials and installation inclusions.
Confirm network export limits, curtailment and the retailer’s feed-in tariff.
Compare the same scope across quotes and confirm discounts are counted only once.
Ask for the self-consumption assumption behind any promised savings, and compare it with your daytime use.

Australian Government Solar Consumer Guide

Simple payback = net upfront cost ÷ positive annual saving. Uses constant first-year generation, usage and rates. Excludes finance, degradation, future tariff changes, replacement costs, system lifespan and changes to supply charges. Payback may exceed equipment life. This is a quote sense-check, not a system design or guaranteed return.

How this calculator works

The calculator values solar used at home at the entered avoided electricity rate and exported solar at the feed-in rate. It subtracts annual maintenance from those first-year savings, then divides the net installed cost by positive annual savings for a simple payback period.

What is included

A site-specific generation estimate, household use and estimated self-consumption.
Avoided imports, export credits, a confirmed discount and an annual maintenance allowance.
Annual savings, net quote per kilowatt and simple payback.

What is not included

Finance, panel degradation, inverter replacement, system lifespan and future tariff changes.
Battery costs or savings, detailed shading and system design, and export curtailment modelling.
Fixed supply charges, rebate eligibility and any guarantee of bill savings.

Worked example

A 6.6 kW system generating 9,000 kWh a year, with 40% used at home, a 30c import rate and 5c feed-in rate, produces $1,200 annual savings after a $150 maintenance allowance. A $7,000 quote with a $1,000 confirmed discount has a five-year simple payback.