We had a small cluster in the basement, with a server for all the backups, a firewall etc. initially for our software development and later mainly for email. I

We had a small cluster in the basement, with a server for all the backups, a firewall etc. initially for our software development and later mainly for email. I just decommissioned it all (still have a few network hard drives for local backup of laptops etc). The power it was drawing was about 300-400 watt. That is 7.2-9.6 kWh/day and 2600-3500 kWh/year. (At about $0.1/kWh.) That is about equivalent of powering a Tesla Model 3 (160 Wh/km) 16000-22000 km, which is about what I drive per year. Our garage has a south east facing roof which with solar panels could deliver about 3000 kWh/year. That installation isn’t terribly efficent due to scale, and would cost me about $15000 to install. Instead we decided to move the email to a Swiss email provider (Migadu) that cost about $4/month. We may install solar panels later amyway, but moving the servers into the cloud cost $48/year and gave us enough equivalent electricity to drive the whole year.