Choosing the right size system for your house could be confusing, usually you will rely on the salesperson to tell you and then you negotiate the price accordingly.

You can calculate the system size by yourself by looking at your electricity bill.

First your look at your average usage per day in kWh. Supposing your usage is around 30kw per day, then you will need to find out pattern of usage

Which means how much of the 30kw you use during the day and how much you use during the night. With more and more people working from home nowadays the usage of the electricity has risen significantly so let say you use 60% during the day and 40% during the night. Now the idea is to get rid of the 60% which works out to be 18kwh.

The average Canberran rooftop receives an annual average of about 4.8 hours of sun per day based on data from the Bureau of Meteorology.This is average figure, more Sun in Summer and less in Winter but let’s say average is 4.8hrs Now if we installed a 6.6kW system with a 5kW inverter it should produce around 24kw – the 25%efficiency loss 24- 25% =18kW. But remember this is only for what you are using during the day which means you might not get and solar FIT because the does not produce enough to export any because you have used all the energy produced in house.

Therefore it is better to size the system by a bit more so it can produce enough just in case you might use more during the day.

Now if you are installing battery system then you will need a bigger size system because if you have just enough to produce what you use there will be none left to store it in the battery to use at night.

I would recommend at least a 13.3kw system if you are choosing to install battery which will then produce enough for you to use during the day and enough to store it in the battery

The Next Gen scheme currently offers a rebate of 50% of the battery price up to a maximum of $3,500.