[Gravityloss]

Hmm, just as a note, at least over here normal electricity companies provide the total level on their web site... no need to install any hardware.

[NortySpock]

In real time?

Mine only gives me a month-to-date, end of month for billing, and month-over-month for the last two years (plus the outside temperature for comparison).

[Symbiote]

My Danish electricity supplier gives hour-by-hour usage, with the most recent hour being 23-24 yesterday, so I assume it updates at midnight.

I don't know if there's an API or something to get almost-current data.

[Gravityloss]

I haven't bothered to check but I think on about hourly level is common.