Go north my friend! http://www.heatinnovations.com/od-boiler.htm
This Canadian outfit makes an outdoor coal boiler.
I'd think the solar unit will work pretty well. Of course he'll need some sort if back up. If the backup doesn't get used much, natural gas or propane would be sweet. Geepers, 4 or 5 yrs ago if you invested twenty grans in a solar unit you'd have been looking at a 15-20 year payback. Now 3 or 4 years of oil prices will pay for about anything! It's sad that so much of our money has to go in that direction. It's going to hurt Maine more than any other state. A far higher percentage of people here burn oil, and our winters are two months longer than any other state....'cept Alaska.
I'm the wrong guy to ask what stoves are hotter than others. This coal thing is all new to me. I've never burned one pound of it yet! When I was a kid a friend of my fathers burned coal for years and years. Looking back and trying to remember when I was 8 or 10 yrs old, I'll bet it was an EFM. It had auto ash removal too, at least into 30 gallon pails. If it weren't for seeing that when I was young I'd have not given coal a thought. I'm sure I'd be burning wood....again.
The dog, "Keeoh" is her name, says "Woof!". We just got done playing Frisbee. She's so funny, smart too. I'll throw the frisbee half a dozen times, then tell her "I tire of red frisbee, I want to play with white frisbee". Well, she'll spit the red one out like it tasted bad and she'll snoop allllll around the house until she finds white frisbee. 10 minutes later we play the same scene with blue frisbee. I know, I know, dogs are color blind.