Having reduced our household (and home office) power consumption 5 fold to 6kWh/day, we can now cover maybe 30% of it with 1.29kWp of PV panel.
http://www.earth.org.uk/saving-electricity.html
Do dig out the kWh number from your bill as TomW says: unless you have gotten down to the low single digits per day solar is not going to be able to make much of a dent!
Rgds
Damon[ Parent ]