Efficient doesn't really mean anything without an thorough understanding of the local energy grid. Distributed solar mixed with wind and some gas peakers? Sure, probably better from a GhG perspective to use restive heat, even if it isn't cheaper cost wise. Running your house on a coal heavy grid with long transmission lines? Yeah, gas is probably better in the short to medium term unless you can get a good deal on solar panels and storage.
All of that's kinda moot though since modern heat pumps are insanely effective, relatively cheap to install, and work down to sub-zero Fahrenheit temperatures using only air-source exchangers.
All of that's kinda moot though since modern heat pumps are insanely effective, relatively cheap to install, and work down to sub-zero Fahrenheit temperatures using only air-source exchangers.