I must be missing something simple but my new emonpi I had just setup is showing the vms as 230V even though I am in US and is plugged into 120V outlet. I assume this is also why I am seeing the watts reported from the CT sensors nearly double what makes sense (3000 watts even though it is on 15A circuit breaker).
Thanks for helping me understand what I am doing wrong. 
I don’t think Brian’s link will help you - yours is a software problem.
It’s because the emonPi actually measures the voltage out of your a.c. adapter, and that’s roughly the same as the voltage out of the UK adapter when the voltage in is 240 V. You need to look at the file emonhub.conf, which you can do through your web browser and emonCMS, and set the flag in line 33 (or thereabout) to 110 V (N.B. this is NOT a calibration, it’s a “flag” that is matched as text.)
Thank you both of you. Step 3. of Brian’s link for the Use in North America does explain setting the config but I must have missed it as well since it was in the “hardware” section and I was looking for a software problem. If I may suggest adding this issue to Troubleshooting - Guide | OpenEnergyMonitor would be helpful. (I looked everywhere in the software section and couldn’t find this info about how to change the voltage).
Also of note for any future readers I had to reset the Power feeds in the CMS since it appears it was not pulling in the new voltage setting so I saw the correct vms values but the watts were still double.
I’m afraid that’s above my pay grade. @Gwil please?
I don’t understand that - unless you mean the power already recorded was double? That of course would happen - the power calculation is done in the Atmel 328 “emon” section before the data hits the “Pi” section and emonCMS where it is recorded. The power that came in to emonHub after you’d edited and saved emonhub.conf and restarted emonHub should have been correct from that moment on.