I'm currently sitting at < 200W, but I expect that to go up with a higher workload. The SER9s idle at 5-7W, but they can run at 50-60W sustained without thermal throttling. Some reviewers have claimed that they can run at 75-80W sustained for 10-15 minutes, but I think that's pretty unlikely.

We have pretty reasonable power rates here (https://www.idahopower.com/accounts-service/understand-your-...), so ~$12-20 per month depending on tier.