Electric space heaters are not really meant to be used as a sole heat source but instead electric space heaters are meant to be used as supplemental heat to your existing forced air furnace or other main heat source.
The main purpose of electric space heaters is to help raise the temperatures of colder areas of your home or to lower your furnace thermostat and heat up a room that you're in instead of the entire house.
To heat an entire house with electric space heaters you're gonna need around 5 of the space heaters running all day and at 1500 watts each those 5 space heaters will use 7,500 watts per hour and at 10 cents per KWH it would cost you around $0.80 per hour to run 5 electric space heaters.
If you run the space heaters for 15 hours per day to heat your home then it would cost $12.00 per day which is expensive.
At $12.00 per day for roughly 30 days in the month those space heaters would cost you $360.00 per month for lukewarm heat.
That gets expensive and natural gas if available would be much cheaper to heat your home with.