You can get central heating boilers (I've certainly seen gas fired ones in the UK) that are actually mini-generators, the heat almost being a bi-product of the electricity generation. More pricey than the normal boilers but an interesting technology.
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 ... LED lights have come on in leaps and bounds over the last five years and greatly reduce your power consumption, though they are not cheap to buy. The upside is that they are supposed to last a LOT longer.
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?