We set the thermostat to the low 50's at night and use an electric blanket to warm up the bed but, with enough solar, you could let it run all night. But we're weekenders and I have no numbers to say if that would save propane or not over your usage. You might be doing something similar already. IMO, this is similar to running the A/C on inverter, in order to get an electric heater big enough to replace your propane furnace, you're looking at A/C level power draws. We've had some good discussions on this and the consensus is that the problem is not battery capacity or amount of solar, it's being able to recharge the batteries for the next days usage. IMO, since the heater only runs a few times at night it's probably easier to run a big electric heater on inverter than an A/C unit.
