Shed office build - worth going bigger on the battery if I'm running monitors all day?

Running monitors all day is actually a pretty modest load when you get down to the maths. A couple of decent displays will draw maybe 40–60W combined — less if you're on modern IPS panels rather than ancient cathode-ray museum pieces.

The more honest question is: what else are you running? Because it's never just the monitors, is it. There's the PC or laptop, the little USB hub, the phone charging, the inevitable desk lamp you "only use occasionally," and then suddenly you've got a 200W draw you didn't account for.

My narrowboat setup taught me this the hard way — I initially undersized my Fogstar lithium bank thinking I'd only be running "light loads," then discovered that "light loads" plus an inverter's own consumption plus a few cloudy days in a row equals a very flat battery and a very frustrated me.

For a shed office, I'd be looking at your daily consumption first, then sizing battery to cover at least two days without meaningful solar input. UK winters are brutal for generation — you might see 0.5kWh on a grim December day from a decent array.

My rough rule: calculate your realistic daily draw, multiply by three, then size your Victron (or whatever BMS-managed lithium setup you're going with) accordingly. You'll thank yourself in November.

What's your current thinking on solar array size? That often dictates the battery conversation more than people realise — a small array feeding a huge bank is just expensive disappointment.

@ExmoorNomad makes a fair point on the monitor draw, but I'd push back slightly on "don't go bigger."

My garden office setup taught me that it's not the monitors that bite you — it's the ancillaries you don't account for initially. Router, NAS, desk lamp, phone charging, the odd kettle run… it all stacks up.

I went with a 200Ah Fogstar Drift LiFePO4 and genuinely wish I'd gone 300Ah from the start. Upgrades cost more in the long run than just speccing correctly at the outset.

Also worth considering autonomy during bad weather — how many overcast winter days can you actually sustain without topping up? That's the real metric, not just peak draw.

What's your solar array looking like? That'll change the equation considerably.

@ExmoorNomad and @CliffWill are both touching on something real, but here's what shifted my thinking when I built out my garden office setup — it's rarely the monitors that sting you, it's the thermal load.

I spent a summer convinced my 200Ah Fogstar lithium was plenty. Then August hit, a small desk fan ran all day alongside the usual screens and laptop, and suddenly I was watching my Victron BMV drop faster than expected by early afternoon.

Went to 300Ah, never looked back.

The monitors are predictable. It's the stuff you forget to budget for — the fan, the occasional phone fast-charge, the router, the desk lamp on grey days — that creeps up on you. Size for your actual lifestyle, not just your headline loads.

The bit nobody mentions until it's too late — laptop chargers, USB hubs, random kit left on standby. I audited my static caravan setup last year with a plug-in energy monitor (like a £12 Energenie from Amazon) and was genuinely shocked. My "just a laptop and two screens" office corner was pulling nearly double what I'd estimated once you count the router, phone on charge, desk lamp, occasional fan...

Go bigger on battery, yes, but audit first. Stick a monitor on the circuit for a week before you spec anything.

On sizing — I've got a Fogstar Drift 200Ah and honestly wish I'd gone 280Ah from the start. The price difference at point of purchase is minor compared to retrofitting later. Future-you will be grateful.

@ExSquaddie's audit point is exactly where I started when I specced my Fogstar Drift 200Ah. Before that, I genuinely thought I had a tidy 150Wh daily load. Then I logged it properly with a Victron SmartShunt over a fortnight and found I was closer to 280Wh once you count the sneaky stuff — router, desk lamp cycling on at dusk, the fan heater's "frost protect" mode doing its thing on cold mornings.

The argument for going bigger isn't really about the monitors at all. It's about the buffer between reality and your assumptions. Your assumptions are always optimistic.

I'd say whatever number you land on from your calculations, apply a 1.5× multiplier and spec accordingly. You'll never sit there wishing you'd bought less storage.