Answer
The gas heater is better.
Work Step by Step
Even though the electric heater is 100% efficient in your house, you must trace the electricity back to its original source. After all, electricity is often made using fossil fuels, and the production of electricity is usually not completely efficient. Therefore, the 85% efficiency of the gas heat, even though it appears to be less than the electric heater, is actually a greater efficiency, for the efficiency of power plants producing electricity is generally below 85%.
