If you adopt an energy coin that always equal to 1KWH to measure value, then things will be priced like 1 ENE, 100 ENE, etc.
Impossible to quantify. Let's take a car for example. How can anyone possibly calculate accurately the energy expenditure required to take that from design to being driven out the showroom? The energy output of the engineers who design it? What about the energy required for the computers they design it on? What about the raw materials of those computers? What about the machinery used to mine those raw materials? What is the lifespan of that computer, and so what percentage of the energy cost can be attributed to this car? Already we are in an unsolvable situation and we haven't even reached the drawing board yet.
The best we can do is a subjective estimate of the value of each individual component, process, material, person, etc., which is exactly what USD does. An objective measurement is impossible.
All the valuation is done by energy input or cost, in short term, fiat money can be used to estimate the value of each component, since they are inter-exchangeable to same amount of energy anytime. For example, if 1 USD can buy you 10 KWH on energy market yesterday, it will be roughly the same today
However, in the long run, and especially during some extreme situation like we are having now. The exchange rate is no longer stable. 40 USD can buy one barrel of oil weeks ago, and now 2 barrel of oil, maybe next week it can buy you only 1 barrel of oil again due to unlimited QE started
Let's take another example, suppose that 1 million Zimbabwe dollar can buy you one barrel of oil yesterday, and now it can buy you 2 barrel of oil today, is it Zimbabwe dollar value doubled or the oil value decreased? Most possibly you will consider Zimbabwe dollar value increased: If you don't have any idea about fiat money's value, then energy would be a much more objective measure of value
Value is driven by supply and demand, but price is driven by supply and demand of fiat money
Just saw this news that reflected how absurd today's fiat money system is:
https://www.commondreams.org/news/2020/03/21/two-1-trillion-coins-rashida-tlaib-proposal-calls-us-treasury-fund-coronavirus