portable electric heaters

But you can't compare just the efficiency of the energy used on site to make heat for your home. There are two factors you have to consider to determine if a small space heater will save you money:
The cost of electricity versus the cost of natural gas heater
The amount of space you're heating and how much heat you're adding to it
If you have a decent sized house and keep most of it fairly cool while moving a small space heater around to keep only yourself warm, then you might save money. The cost per Btu of heat for portable electric heaters is generally more than double the cost per Btu for natural gas, especially with gas rates as low as they've been in recent years. It can be 3 to 5 times more than natural gas in some areas