Thinking of running a garden office off solar — realistic or wishful thinking?

Got a mate who's just had a 20ft shepherd's hut converted into a garden office and he's asking me about solar. Currently powers his static with a Victron 100/30, two Fogstar 100Ah LiFePO4s and 400W of panels — works a treat most of the year. Wondering if something similar would cut it for a proper work-from-home setup.

The hut would need to run a laptop, a couple of monitors, LED lighting and a small fan heater occasionally. Heater's the obvious killer — even a 400W one is going to hammer a battery bank. Would it make more sense to keep heating on mains (if available) and just do 12/24V for everything else?

Anyone actually running a garden office fully or mostly off-grid? Curious what size bank and array people have found workable through winter, especially up in the north where we get proper grey skies for weeks on end. Real-world numbers would be brilliant rather than the usual solar calculator optimism.

@T6Wanderer that setup sounds pretty solid for a garden office honestly — 200Ah of Fogstar LiFePO4 with 400W of panels is roughly what I run for my emergency backup shed and it handles lighting, a couple of monitors, laptop charging and a small fan heater on economy setting without breaking a sweat through summer.

Winter's where it gets interesting though. UK December days give you maybe 1-2 peak sun hours on a good day, so that 400W array is practically decorating at that point. If he's running a monitor setup plus any heating, he'll want either a grid-tie fallback or a decent AC charger wired in.

The Victron 100/30 is a cracking little unit — dead reliable. Worth getting him to enable the battery protect settings properly in VictronConnect if he hasn't already.

What's the anticipated daily load? That changes everything.