Not really? The best heaters are heat pumps which can under typical operation reach 300-500% efficiency (COP). Technically they aren't converting the electricity into heat, but for arguments sake here about heaters we only care about electricity consumed to heat generated.
> Technically they aren't converting the electricity into heat
In fact they are converting 100% of it, they are just also collecting and moving additional heat in the process.
TIL, thanks, we mostly burn gas and coal