Solar Roof Calculator
Find out whether the rooftop solar rule applies to your connection, how many kW it asks for, and whether your roof can carry it. Takes one minute.
Your connection and roof
Six answers. We tell you whether the 20% rooftop solar rule applies, what size it asks for, and whether the roof can take it.
- Rule check for your approved load
- Roof area check
- Roof readiness light
kW
- Mandatory?
- Roof space
- Roof readiness
- Time left
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Leave your details. Our engineering team replies with what we need to see. Your answers and the result above are sent with your request.
Rooftop solar: common questions
Who has to install rooftop solar equal to 20% of the load?
A new electricity connection, or an increase of load, with an approved load of 10 kW or more must install solar equal to 20% of that load. Existing connections with no change of load are not covered, and may still choose to install solar under net metering.
How much roof does solar need per kW?
Roughly 60 to 70 square feet of free roof for each kW. Walkways, setbacks, water tanks and shade take part of the roof, so the usable area is always less than the total area.
What does the engineer's roof check cover?
An engineer inspects the roof structure, checks the purlins, rafters and connections by calculation for the extra weight and wind load of the panels, and states in writing whether the roof is safe as it is, safe with strengthening, or not suitable.
What is the 28 February 2027 date?
Systems installed before 28 Feb 2027 qualify for the current net-metering export rate. Installing early keeps you inside that window.
This calculator gives a first indication only. Every roof needs an engineer's structural check before solar is installed.