I like the idea of a nat. gas boiler; we have gas at the house so it would be nothing to run some black or copper pipe out to the shed. Problem is the price; I haven't seen any of those heaters for under a $1000. The lowest the temp ever gets in the winter here is about 40-maybe high 30's; and that lasts a night or two here or there over the whole winter. Summer starts in April practically with close to 80 temps and from there 90 to 95 til Oct!! So maybe I could get away with a cheaper way; an electric water heater for instance on the really cold nights. I could also make some type of arbor (which I am leaning towards anyhow) and have removable plastic panels to keep the heat in, almost like a greenhouse style structure.