You have a few options for keeping tabs on your supply voltage/current and consumed watt-hours. You could buy
an inline meter ready to go, or get just the meter and add powerpoles to it, or assemble your own meter in a box.
The basic inline meters come in crappy and okay varieties, but can be glitchy or just plain inconsistent, but it's a
bit of a project to build a decent meter, so you can decide if it's worth it.
I initially bought a bunch of the "45 amp" (commonly listed at up to 200 amps!) generic meters, they go by every
brand name, in the book. They also tend to come with thin wire (18ga or so) and I've been able to adjust the
current reading by slightly flexing the case, so they don't inspire my confidence. But they can be very inexpensive,
so I suppose I'll give them a pass for what you pay. PowerWerks slaps powerpoles on them and triples the price.
Wanting better quality and more features, I've taken the time to make my own custom inline meters based around
a higher quality panel meter. It has a lower current rating, but a higher voltage rating, as well as some other nice
features that make it better to have as a tool than as a permanent installation.