This is not even something anyone can measure let alone come up with an estimated percentage!
Simply because no miner in their right mind is going to publicly announce that they are mining bitcoin specially if they have a rather larger operation because they may become a target for theft or worse.
Since we don't know who is mining and there is no directory where they register, we also don't know what type of electricity they are using.

These guestimates are always either FUDs or wrong numbers based on the small portion of the mining community that has revealed their operation like a couple of big mining farms (eg. 15% of the total hashrate) that went public.