Look, it's sexy to complain about energy costs, but you are really underestimating the massive inefficiencies involved in the legacy payment system. Because even if bitcoin is less energy efficient in some technical sense, there are enormous efficiency gains it provides by inverting the structure of risk in the payments industry.
One of the first things you realize when you try to setup payment processing is that middlemen would not actually exist in the payment processing industry if it was an efficient market. But these companies do exist because the entire industry structure has developed to pass risk from credit card companies to intermediary businesses whose sole function is basically to manage risk and enforce policy compliance. It is a bit like if Google didn't give email addresses to individuals because it couldn't be bothered policing spam, so you got your email through a third party.
Anyway, even if we ignore the deadweight losses imposed on the economic system by all of the businesses which cannot get credit accounts (merchant accounts), the costs of supporting this credit-centric system are enormous. PCI compliance costs alone are staggering, and serve no purpose except to lower the risk held by credit card companies. And even with this, the inefficiency of central risk management is so great that VISA doesn't even bother to investigate fraudulent purchases of less than 500 USD. And why should they when costs can simply be pushed back to merchants and turned into a profit center by issuing chargebacks.
And this is where bitcoin gets interesting -- by inverting the risk structure and letting anyone accept payments without the need for a payment processor to issue credit, Bitcoin eliminates entire horizontal swathes of the payments industry, while placing competitive pressure on legacy payment providers. If the technology scales to the point you are concerned about, it will decimate the number of people required to be employed managing risk in everyday transactions.
Put more succinctly, you need to shift from thinking about the energy costs of bitcoin as a wasted ongoing expense and start considering them the price of eliminating an otherwise intractable trust problem in finance. It is like paying for a standing firefighting force. Expensive in one way, but a lot cheaper than the alternative.