Are infrared heaters hard on your power bill?

Heat is heat. All heaters are exactly 100% efficient. IR heaters are uncomfortable because they only heat by line-of-sight. Like backing up to a fire, only one side gets the heat.

Poor insulation is what's hard on your power bill. Count your electrical outlets and light switches on outside walls. Go to a hardware store and get foam insulators for them. Locate all cracks around doors and windows and seal them with glue or tape. The crack under the entry door is closed by a "sweep" and that comes from the hardware store too. If your windows are cold, get a sheet of Styrofoam and cover the glass. Ask the clerk at the hardware store for more suggestions.