Solar PV panels have an advantage and a reasonable payback around 3-5years depending on the size installed, but the real savings come from solar/heatpump hot water systems.
I have used solar roof top panels for 30 years and about 5 years ago upgraded the HWS to heat pump model and my annual hot water bill is around $50, whereas if using a standard hot water service it typically would be around $400-$600pa depending on the number of kids home.
Also at the moment if you hunt around you can get new heat pump hot water systems fully installed for less than $100 if you are replacing an old off peak electricity powered HWS.
My point is don’t just consider solar PV’s you have to consider the savings of solar/heatpump hot water.
