The common use terms for the size of an installation

In the article on Electric Vehicle charging this paragraph appears…

‘Generally, it will take a full day to charge an average EV from 20% to 80% using a common 6.5kW rooftop solar system’

This term 6.5kW (or maybe 10kW) is used a lot in articles on home Solar installations.

Surely this is misleading because the correct terminology is 6.5kWpeak - this being the best that the panels could ever produce in a laboratory environment or in the middle of a desert in Chile at the best time of day on the best day of the year. It is nothing to do with the amount that you would actually produce on your house.

People tend to relate this 6.5 figure to either the kW that will be generated each hour average or is somehow is related to the charging of the Batteries, which of course is measured in kWh.

How should we best describe the ‘size’ of a house installation?


Hi @dicktrimmer5544

We would describe that in kW. We don’t really use the term “kW peak” in normal parlance in the Australian residential solar industry, but you are correct, that it what we are referring to.

The 6.5kW and 10kW figures we refer to are “peak”, which is to say the cumulative nominal figure of all the panels installed on the roof, I.e an installation with 18 x 370W panels would be referred to as a 6.66kW system.

We have this post to explain the difference between kW and kWh


The main problem with Rooftop Solar is that they are commonly Fixed in Place, and facing One direction, even if panels are installed in different directions, each Panel is ONLY be able to Generate Peak Power for approx. 2 hours, and that is when the Sun is perpendicular to panel, then for the remainder of the day will Only be Generating Shoulder Power.

So, All Fixed Tilted Panel Racking basically equates to 5 Hours Generation per Day,

EG: 10kW Array will Generate using 20x 500W panels will Generate approx. 50kWh of Energy per Day!

Where a 10 Panel Dual Axis-solar Tracker (DAT-10) using 500W Panels will Generate 50kWh of Energy per Day, with 10hours of Sun, the further South of Sydney, a DAT will Generate 12hours of Peak Power.

DAT’s are like an Old-school Hills Hoist with Solar Panels fitted atop a Pole.
DAT’s are also able to mount a Vertical Wind Turbine above the panels.

I believe in using Less Precious Metals & using Half the Panels!


Thanks a lot for this straight forward explanation


Thanks a lot for your response. This aligns with my thinking. My 10.26kWp system is yet to be installed in Spain and I am expecting 40kWh per day in July but only 18kWh in December.