I'm hoping to get some advice about boiler sizing. I had a heat loss done a couple of years ago, it came out at 130,000 - there was of course some guesswork involved in that. That includes 14,000 for the cellar which we have never done as there has not been a real need (it's cool but not cool enough to cause problems). Using their numbers and taking off the basement, that's 116,000. Now, the real world: using a mod/con gas boiler (155,000 BTU) with outdoor reset. The reset curve is set at 70 (low) and 135 (high) so by my calculations based on the EDR of my rads, I'm only putting out maximum 90,000 BTU at 135 degrees. This seems about right as I've not seen the boiler stay above 50% for any sustained period. Design temp is -10F. We only rarely hit design temp here, often it's much warmer, around 20 F. I'm expecting to have about 1300 gallons of unpressurized storage in an old cistern that I'll insulate and line. Given these numbers, what size of gasser would you put in? I'm very seriously looking at a used Tarm Excel 2000 which I believe is 30KW - I think it would handle the load okay. I'm also not averse to the gas having to kick in on a very cold night - every night on the other hand is not what I want either! Other possibilities are Tarm Solo Innova 30 or 50 as well as Vigas 40 - I think a Vigas 25 would be too small.