Estimating the cost of running the heater is a piece of cake. Just take the input power in kW and multiply it by the price you pay per hour for energy. So, if the input power is 4000 watts (which is 4 kW), and you’re paying 7 cents per kWh, that will be 4×7 = 28 cents per hour.
If you keep the heater on for 5 hours daily, that is 28×5 = 140 cents daily. Per month, it will be 140×30 = 4200 cents or 42 dollars.
Tips: If you use an electric garage heater 120V is very cost effective items.