Sorry if that's a misleading title... my water is not green. But I'm looking for some advice on a long term plan for my house which will hopefully reduce or eliminate my need for fossil fuels.

One of the top issues will be whether to replace my oil fired boiler which is used both for our radiant baseboard heating and for our hot water. I am not the original owner but the boiler has a date of 1998... making it only 10 years old, and so I assume not terribly inefficient compared to some others on my 60 year old street.

Our house is 2000 SF +/- and we may be adding on another 500ish SF as part of our renovations... which will also require additional baseboard or another heating solution. We're very well insulated and have new double pane windows... though I could probably add a bit more insulation in our attic. Natural gas is not available here. Currently it's either oil or electric. During our future renovations I may add propane for cooking and possibly as a primary or backup source for heating water. However I'm hoping instead to eventually integrate as much solar power with battery storage as I can reasonably afford and use that electric to (among other things) meet our water heating needs if it is feasible.

I've been looking into various options and was wondering about using a combination of tankless water heaters, solar water heater, and perhaps an indirect heating system with an efficient storage tank. My gut says not to rely on a whole house tankless system to do everything, especially not an electric one. But I'm not opposed to spreading multiple smaller units out where they can be most effective and/or combining with other technologies.

The biggest questions I have are around the idea of using an on demand tankless system in conjunction with my existing baseboard radiant heat. It seems I might want a dedicated unit for that which could be turned off during warmer months. I'm not certain what the power demands would be for such a unit or if it could generate enough hot water to keep up with our winter heating needs. I've read several TOH postings here about indirect water heating systems and wonder if that could be used in conjunction with an electric tankless heater to resolve such potential demand issues. I've also wondered about chaining two tankless systems in a pre-heat/heat type series if one unit cannot meet the demand. Similarly I've considered a system that circulates the water up onto the roof to be heated by the sun... and then running that preheated water through the electric tankless unit... or do I have that process backwards?

My ideal plan would be to generate enough electricity with solar collectors to power these water heating units as well as most of my other electric needs... but I realize that may be cost prohibitive. And I wouldn't want to put myself in a position where I add so much to my electric consumption that it eliminates any savings I might gain from adding solar power.

Obviously I'm still in the paper and pencil phase of this plan and everything is working well enough for the moment. So all ideas are welcome. Education is what I need most at this point.

Thanks in advance.