With the average kilowatt per hour energy cost in the U.S. hovering around $0.16, and the average electric fireplace using about 1.5 kilowatts, you’re looking at an added cost of approximately $0.24 per hour. Of course this number can vary based on the size and precise energy requirements of a given fireplace model — as well as the per hour cost of energy in your specific location (as little as $0.11, or as much as $0.30).
Looking at just the averages, running an electric fireplace for 24 hours could add around $5.76 to your bill per day. On a particularly cold month, that could mean an extra $172.80 to $178.56 — if you left the fireplace on all day, every day.
If you ration its use out to something more typical, like about 8-10 hours per day, then you’re looking at something more like $1.92 to $2.40 per day. So about $57.60 — up to $74.40 — more on your monthly electric bill, if you use the fireplace every day for that long.
Just how much is “too much” added cost for your monthly expenses is purely subjective, but in the grand scheme of things, an electric fireplace won’t incur much on a per hour basis. What it really comes down to is how many hours per day — and over how many days — you end up using it. As always, if you’re trying to save on the monthly bill, the key is moderation.