[sbenitoj]

That's not strictly correct, the difficulty to mine Bitcoin has increased massively over time:

https://bitcoinwisdom.com/bitcoin/difficulty

Every 2016 blocks the difficulty adjusts so that ON AVERAGE a block is found every 10 minutes. If the hashing power of the network is increasing over time, the amount of time it takes to find a block goes down (can be less than 10 mins) as it approaches the next difficulty adjustment (and vice versa).

But you are correct that as the hash rate increases, the total power consumption increase along with it -- at the moment there is no proven alternative.