Welcome, Alan, to the OEM forum.
Probably not - so I’ve moved you. I doubt you’ll be wanting just an ESP8266.
That’s a big problem, especially for someone new here. In a nutshell, we’ve been hit by the global semiconductor shortage and so we’ve recently launched a new energy monitor, the emonTx4 (the mainstay of our energy monitoring system), which has a completely different processor to its predecessor. On it’s own, this only gathers data and sends it somewhere. The ‘somewhere’ can either be a Raspberry Pi running our own emonCMS (which incorporates databases etc) or an on-line version at emoncms.org. You will probably not want the on-line version.
So my advice for a starting point is to look at what the emonTx4 is capable of, and then try to get your head around emonCMS. But a warning - we’re also in the throes of re-organising the documentation, so you are likely to come across dead links (notes of their locations all gratefully received 
).
You’ll also see the emonPi - this is a 2-channel version of the (old) emonTx and a Raspberry Pi all in one box.
Whatever else, don’t be afraid to ask. There’s only one stupid question - it’s the one where you assume we know what you’re thinking - so the more you explain what you want to do and what you have, the better we can help you.
From what I know about what you’re planning, I suspect you will probably need to design and build your own hardware, as the emonTx/emonPi/RPi is designed primarily for whole-house monitoring. But if you do want to purchase from The Shop, until you’re really familiar with the hardware and what can be 'mix and match’ed, do bounce your shopping list off us before you order.