Calculation Methods & Assumptions

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1. Disclaimer

This is purely a simulation. The results provided by this calculator are estimates only and may differ from actual invoices.

This calculator is designed for residents within the ACT, primarily for Canberra residents, and uses assumptions and values specific to this region.

Results may change depending on:

Important: This calculation result is not an official quote. This tool is designed for educational purposes to help you understand the potential benefits of renewable energy and does not constitute financial advice.

2. Key Assumptions

This is the place to check when you wonder "Why is it this amount?". We present the key values used in our calculations in a table format to increase transparency and reliability.

Data & Assumptions Used (as of Nov 2025)

We use the following values based on current market data and government reports:

Parameter Note
Average solar generation We calculate average solar generation as 4.3 kWh per kW per day. According to the Your Home website, this is based on standard photovoltaic system performance data for Australia.
Electricity Purchase price We use $0.33/kWh as the average electricity purchase price for Canberra.
Feed-in Tariff Feed-in Tariff is the rate at which excess solar energy exported to the grid is purchased by electricity retailers. We use $0.06/kWh as an average value.
ACT rebate If eligible for the ACT rebate, you can receive a discount of up to 50% of the installation cost, with a maximum rebate of $2,500. For more details, please check the ACT Climate Choices website.
Emission factor We calculate the emission factor as 0.64 kg CO₂/kWh. According to the National Greenhouse Account Factors 2025 document, this is based on the average emission factor for Australia's electricity grid.

Note on calculation assumptions: Our calculations include appropriate assumptions for panel and battery capacity degradation, bill inflation, and battery losses. However, we assume a panel lifespan of 25 years and do not account for removal costs, maintenance, or other expenses after this period. For long-term installations, additional costs may be required.

3. How it works

We explain the calculation mechanism in simple terms.

Where Your Savings Come From?

Your annual savings are calculated from two main components:

Use it

You save $0.33/kWh
Daytime Self-Consumption
Using solar energy directly in your home during the day avoids buying expensive grid electricity.
Battery
Stored solar energy used at night saves you money at the same rate as direct self-consumption.

Sell it

You earn $0.06/kWh

Surplus electricity is sold back to the grid at a lower rate. Any excess solar energy that you don't use directly gets exported to the grid.

What is the Payback Period?

The payback period is the number of years until your total annual savings exceed the initial installation cost (after rebate).

We calculate how many years it takes for your cumulative savings to cover the upfront cost of installing your solar system. This helps you understand when your investment will start paying for itself.

Why Batteries Make a Difference

Without a battery:
You only use free solar power while the sun is shining. At night, you're back to paying full price for grid electricity.
With a battery:
You store the surplus energy generated during the day to use at night. This maximizes your self-consumption and minimizes what you buy from the grid.