Hi Mik, hope I'm not carping on too much about off-grid, but here are a few of my lessons learned over the years:
My first obs was in outer suburban Brisbane and close by the house. It ran very reliably off an extension cord and a Cat 5 cable, with a largish (8A) 240 /12V supply providing juice to all the gadgets. Had a desktop PC with monitor
out there as well, so the 240V was used for that as well as feeding the 12V supply. This overall approach is good and also simple, providing the AC and Ethernet connections are nearby.
My present obs is also within extension cord and ethernet range of my shed, where my house off grid solar equipment and LAN monitoring system is located. However I started out thinking that as I had spare batteries and panels, and a LAN connection back to the house, I might as well just go solar for the obs. I no longer wanted/needed a full blown PC in the obs, preferring to do things remotely from the house, using a simple NUC velcro'd to the CEM60 mount, which was wifi'd about 2 metres to the Access Point/ethernet run to the house. This setup also works well, but I eventually had the occasional need for a soldering iron, etc in the obs so ran an extension cord for that. All works fine.
I considered using a laptop for the obs computer, and purchased a cheap 12V to 19V converter off Ebay, which worked well, and is still available in the obs, but I went with the NUC instead, as I could put it on the mount, reducing cabling dangers and eliminating any need for laptop power sources. If of course you plan on working out of the Obs, then a Laptop with its built in screen is a nice and simple approach.
BTW, low power 32" LCD TV's 1080p 240V/12V with HDMI and VGA inputs are readily available and make a good monitor if you want one in the obs.
An Ebay 4K passive HDMI switch will allow you to select various HDMI video inputs should you wish.
So to summarize, in my opinion the extension cord approach or the solar with extension cord charging backup are both reasonable, with the extension cord preferable if you'e going to work in the obs using a PC/Laptop. Full solar off grid only if there's no easier way. YMMV
