How much energy per transaction?

Question

Assuming a fee of .033usd per transaction and an average energy cost of .141usd per kwh, it takes .033 / .141 = .234kwh for one transaction.

Another way to calculate it is if there are 17921 transactions in 679 blocks in the last 24 hours, that's 26.4 transactions per block. The difficulty at time of writing is 223130858736, which means that it takes 22kwh for one transaction assuming a Ryzen 5950x at 21000 hashes per second drawing 200 watts .2*223130858736/26.4/21000/3600

That's a pretty big discrepancy...

Looking at the block reward, 198.92usd / 26.4 transactions / .141usd per kwh = 53 kwh

Are there any other ways to calculate the energy cost? Am I forgetting to factor something? Which method is most accurate? Will the energy cost change? If so, how and why?

Answer 1

The difficulty number isn't helpful to your calculation. Let's try this way:

The total network hash rate is 1.78GH according to https://monerohash.com/# on Jan 14th 2021. Let's say your Ryzen is getting 21,000 hashes per second at 200 watts. The network runs on a much more diverse set of CPUs than this fancy chip, but just to arrive at a number... that's 1,780,000,000 hashes/sec / 21,000 = 84,761 Ryzens. At 200 watts each, that's 16,952,200 watts. At 0.10 USD per kWh, the network burns $1,695.22 per hour just to secure itself. With blocks at the regular 2 minute frequency, 30 blocks per hour, that's 1,695.22/30 = $56.50 per block in electricity.

At our current transaction rate of about 900 transactions per hour, that's a nice round 30 transactions per block, so about $56.50/30 or $1.88 in electricity to do a single transaction. Of course, blocks can get much bigger, and we could scale up to many more transactions for the same amount of energy. It's probably best to just stick with the high level total hash rate divided by hashes per second of a reasonably efficient chip.

This estimate is probably low because the network is surely not using Ryzen 5950x's by and large.