The problem is that it's the bitcoin value that is driving the electricity consumption, not the other way around. If bitcoin value drops, the miners with the smallest margins (i.e. old equipment or high electricity costs) will simply switch off their equipment. If the bitcoin value rises, there will be more investments in mining rigs and more electricity consumption.

Consider what will happen if the bitcoin raises tenfold in value (once more) - I do worry a bit on the impact on global energy consumption, electricity may become more expensive when used for other purposes.