I'm surprised that with that unit you would have to supplement?? Those look pretty pricey. You would think that unit would suffice. I have been running an oil filled heater since winter hit to keep my ambients up at 75 degrees and I saw my electric bill double. So, I decided it would be cheaper to run my home furnace set at 74-75 degrees instead.

Luckily, I like to be warm so it doesn't bother me at all. I will see if using more natural gas ends up being cheaper than electricity use.