A while back,someone brought up the problem of switching stuff on
automatically only when the PV panel can meet the load. ie as weather
conditions allow.

Answer is here, someone is making one.
http://www.solarpowerportal.co.uk/ne...management9876

So you can set this up and go out to work. When the PV output meets the set
level it will switch on (and off).
Prevents inadvertent use of non PVpower.