The Solar Guide
How Big is Too Big (or Small)?
The size of system you need depends on 5 main factors:
Your daytime energy consumption
Your local Feed In Tariff
Your local network rules
The size and layout of your roof
Whether you have a 3 phase or single phase supply to your house
The key point to realise is that the ideal solar system size no longer hinges on the size of your current power bill.
10 years ago it was different. Then solar cost about $2,500 per panel. Determining the right system size required an engineer like Finn Peacock from SolarQuotes or a really good installer to calculate what will maximise self-consumption and minimise surplus returned to the grid. You had to consider every panel you added really carefully.
Today the cost of solar is closer to $200 per panel (90% cheaper).
According to Finn, the #1 regret he hears from solar owners who have experienced the bill busting value of solar is that they wish they had bought more panels. There are two reasons for this:
Bigger systems are much cheaper per panel than smaller systems.
Most Australian postcodes get a good price for selling their surplus solar back to the grid.
So, if solar stacks up even if most of your solar energy is returned back to the grid, what is the right size for your home?
According to Finn it’s simple:
“For most people the ‘sweet spot’ is simply a 6.6kW system with a 5kW inverter.”
Without going into detail - this size is where you get maximum kW for your money. If you have a high daytime consumption your payback will be spectacular. If you have low daytime consumption, but a reasonable Feed In tariff (10-16c per kWh) you payback will still be good - thanks to the low cost of panels these days.
Of course if you have a huge daytime consumption, a large roof and a 3 phase supply, you can go much bigger. Often you’ll be allowed to add up to 30kW of panels.
A note about self-consumption
The benefits of solar are about three times (2-3x) greater when you self consume solar. A typical household can work on these approximate rates for energy:
Consume from the grid
30 Cents / kWh
Return excess to the grid
YOU ARE PAID
10 Cents / kWh
Your system makes energy in the day. The more time at home during the day - the larger the system.
Households which benefit the most from solar include:
Weekend homebodies, families with children and retirees
Households with large appliances (pool, heating/cooling)
Pro Tip: The average AUS rate of self-consumption is 30%. Most systems we finance are cash-flow positive from day 1 down to a self consumption rate of 20%.
Read Finn’s 7 Mistakes Solar eBook here for more details on this.