In almost every place I know, using electricity from power company is the most expensive way to heat up an area.
British Thermal Unit (BTU) is the preferred unit of measurement for energy in USA. 1 BTU is "the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit". But 1 BTU is a small amount of energy. It is more convenient to use therm (THM), which is defined as 1 THM = 100,000 BTU.
When your gas furnace burns the gas, it generates heat. The amount of heat generated by burning a cubic foot (Ccf) of gas is always the same: 1031 BTU. How much dollar per THM is that? Your gas bill should include the dollar price of a THM which makes the calculation easy. My bill for December shows that the peak rate is $0.4604/THM.
With electric heaters, all heaters no matter their make and model and price and quality, always output heat at the rate of 3412 BTU/KWH (Kilo-Watt Hour). This means, if you have a 1000 Watt (1KW) heater running for an hour, it will release 3412 BTU in the form of heat.
Electricity bills usually show rates in dollar/KWH. Multiply that by 29.31 to get to dollar/THM. For example, my electricity bill is $0.06/KWH which calculates to $1.76/THM.
So, heating my house using natural gas is 3.8x cheaper than using electricity.
That said, I do use electric heater regularly. I use electric heater in my small, enclosed computer room. It does not take long to heat the room and it has pretty good insulation that the heat stays longer. When I'm planning to be in the computer room for a long time (more than an hour), I turn off the gas furnace that heats up the whole-house.