I've had three or four different propane heaters over the years ranging from 35 - 120 k. btu's. They're generally good but there are some drawbacks. As the temp drops the fuel in the tank doesn't vaporize as well.It's not hard to freeze the regulator or the tank itself.
The other downside is that the thermocouples don't seem to last more than a year or two. ( It's that safety sensor / thingy that allows fuel to flow to the burner.) Once that goes the heater won't stay running.
If you're looking at propane you might want to verify that replacement parts readily are available.
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