I do this with a cheap (~$20) USB RTL-SDR – no Arduino or custom electronics necessary. Of course, I only use it to monitor my own energy usage (electricity and gas) using rtlamr[1] and a script that periodically sends the data to InfluxDB, then displayed using Grafana.

The result is a smart home energy monitor that doesn't require any clamps near the electrical panel, and it exactly matches the usage for which I'll be billed.

[1] https://github.com/bemasher/rtlamr

And then promptly get bored. It's in the same category as running wifi deauth attacks - fun for 5 minutes.

I think most of the modern gear uses ZigBee’s publicly document smart energy protocols. It’s encrypted.

I live in a townhouse and our meters are outside next to where we park our cars. I can read my neighbors energy usage whenever I want.

One uses more electricity than I do and the other less.

I've never had a meter reader enter any house I've lived in, which would be somewhere around 15 different units. All gas/electrical/water meters are on the outside of the house/apartment whether they were smart meters or the traditional ones. Anyone can walk up to them and read them. The digital or analog dial readout is not locked/secured/obscured in any way.

Use SDR networks to do it from afar.

http://www.websdr.org/

Or better still, kill your own meter and have something ping out a reading thats 100 times less expensive.