Solar energy is produced by the suns action on a panel producing electricity or heat for hot water or air.
Notice that on you energy bill that hot water and heating is the largest component so this is where you get the best value for dollar spent on solar.
Light is about 10% of the bill,refrigeration is another 10% so if your bill is $100 then the light and refrigeration component is about $10 each.Heating is the remainder 80% or $80.
One solar panel for electricity with one battery operating only lights will save you $10 off the bill.
One panel and battery and lights on a stand alone system would cost you about $1000.
This being the case it will take you 100 bills to pay you back or four bills per year times the years 25 . 1000 divided x 10 = 100 divided x 4 = 25 years.
So this is not a good return for your money.
On the other hand solar hot water is different that is $ 80 x 4 bills = $320 / years x 10 years = $ 3200 which is the cost of a solar hot water system.
This is not taking into account the government rebates which is the similar for both electric generation and hot water.
If I were spending your money I would go for hot water followed by insulation of your home first in that order...cheers Stewart