Well, since bitcoin only supports a maximum of 3.5 transactions-per-second [1] we at least have an upper boundary on its excessive waste.
1. http://www.altcointoday.com/bitcoin-ethereum-vs-visa-paypal-...
1. http://www.altcointoday.com/bitcoin-ethereum-vs-visa-paypal-...
3.5 Tx/s stays steady and the price increases the power it takes will only increase because miners will turn on more machines but due to increased difficulty will mine the same amount of bitcoins.
A clear example of tragedy of the commons. Where the commons is new blocks. And the tragedy is the waste of electricity and labour.
Let's imagine someone makes a $1000 transaction with a $10 fee and a $10 block reward. This means a miner is at most willing to pay $20 worth of electricity to get that block.
Increasing mining efficiency only gives you an an advantage over other miners. It does not increase the profit per watt because the difficulty will automatically rise until the desired interval between transactions has been reached.
Increasing or decreasing the amount of transactions per block or interval does not directly change the energy consumption. Increasing the blocks per second by 10x means reducing the difficulty by 10x for each block but the total difficulty stays the same.
More difficulty = more hashes needed to mine 1 bitcoin = more machines added = more difficulty = more hashes....you get the idea.