[ikeboy]

Hash rate going up doesn't directly imply more electricity has been used. If it's because more efficient miners have been deployed, they could be using the same amount of electricity for doing more work.

The relevant number is bitcoin's price*the block reward. That's exactly how much one block is worth, and so that's how much it should cost to mine one block. If it diverges from that number then either miners will turn off or new miners will turn on.