My Harmon XXV is one of the high end units, and it doesn't draw anywhere near 20A, otherwise it would need to be on a larger circuit, and not have a 20A plug on the end of it.

I think my electric ignitor only uses 3-4Amps, and running its much lower. I have a Kill A Watt meter on mine, so I track my power usage, will try it out and post the amperage.
And, mine has no chimney at all, I direct vent straight thru the wall. The manual strongly suggests some vertical pipe on the outside, but every dealer that has models hooked up has them straight piped out.
You do need to clean the pipe every year, but it's a lot easier than cleaning a chimney.
I noticed the other day at TSC that pellets are cheaper this year, down to about $215 a ton here. They are sometimes up at $260 or more. Pellet prices are always cheaper this time of year, and increase in the late fall.