We looked at heat pumps and were told that they don't work with very low temperatures (forgot what the temp is) just when you would need them most!
We did a lost of research and decided on a ( Hargassner) wood pellet boiler to replace our old oil boiler that runs wet mostly iron radiators. We had it installed last November. We are extremely pleased. It is very economical and very easy. In fact we are paying out a fraction of what we did on our old inefficient boiler that we didn't use but a portion of the day, we now keep our old drafty stone house warm and toasty all day for a lot less .
The plumbers did build a silo that holds a little over three tons of pellets. Hargassner does offer silos ready made but we needed a special size to fit our cellar. We have a local wood pellet (granule) company that delivers three tons of pellets at a time and they have a special blower that automatically blows them in the silo where the boiler uses the pellets automatically.
Can highly recommend it!
By the way, we did receive a tax refund on the boiler less labour. Not sure what it is this year but believe they may have increased the rebate on this and other green installations.