The customer doesn't care either because a page that takes 5s longer to load on a 1W TDP SoC costs them around one-millionth of a penny. Even if you're refreshing 100 times per day it's only around 0.05 kWh per year, which at any reasonable electricity prices is a sum that's simply not worth worrying about. You'd get more savings from getting people to turn off their led light bulbs for a few minutes.
Also, it's not just your site. It's every site. And the customer pays all those millionths of a penny added up out of their pocket. And all those 5 second delays out of their lifetime.
Edit: btw at a quick glance you underestimated cell phone soc TDP by a 2-4 factor.
A single use of an electric kettle sounds like it would completely dominate this consumption.
The time cost is certainly the greatest expense here, power is cheap in consumer computing contexts, generally speaking (at least nowadays with most things racing to sleep), and is mostly relevant because of battery life, not power cost.
