Do I use both clamps on the HEM v1?

Just received the HEM v1. Instruction seems to say you only need one of the two clamp to go into the breaker?

Also, how do I tell which version firmware I have?

If you have 2 120v feeds (240v USA Service) then one clamp for each feed (line).

You could just use one of the clamps but in my breaker box I connected each clamp around each phase coming into my house. So in my case if I only connected one clamp I wouldn’t get the full report of power coming into my house. You can tell what firmware yours is at by clicking on Settings and looking at the version as seen in the attached screenshot. If you just purchase the v1 you will want to follow my guide here and update the firmware:,29935.msg212553.html#msg212553

Thanks, looks like I have version 3,2,78,3,60 any reason to update it to 367? I seem to be getting real time reporting. I went ahead and clamped both to each of the wire. I have 3 devices showing, I assume one is the main unit and the other 2 is each of the clamps

But the # doesn’t add up,
clamp 1 - Watts292KWH17.6910
clamp 2 - Watts827KWH31.5350

the HEM with the battery icon - Watts1493KWH49.2440