Comment Re:The number one thing (Score 1) 250
If you can setup your roof solar panels (be they solar thermal or solar PV) to follow the sun that should increase efficiency, but it might be marginal. I've also seen a lens system fitted over a solar panel that concentrates the solar radiation.
Next is to try and cut down on your power usage
Air-to-Air heat exchangers might be an option too, and certainly using heat exchangers to try and not flush your heat out might be worth a look.
EG when you have a shower the water that goes down the plughole is only a handful of degrees cooler than when it came out the shower head. Could you use a heat exchanger to take heat from the 'waste' water and pre-heat water going into your hot water cylinder?
EG If you run a clothes dryer, are you venting the air directly? Could you run that through a heat exchanger to pre-heat fresh air coming in?