Powering my new garden office - gone completely off-grid, anyone else done this?

Finally got my 6x4m log cabin up last month and decided against getting the sparky in to run a spur from the house. Felt like the perfect excuse to go properly off-grid with it. I've ended up with 2x 200W panels on the roof (south-facing, slight 15° pitch which I know isn't ideal), a Victron SmartSolar 100/30 MPPT, and a 200Ah lithium battery from Fogstar. Total spend was around £1,100 all in, not counting the cabin itself.

Day-to-day it's handling my laptop, a couple of monitors, LED lighting and a small USB-C hub no bother at all. Running a 60W desk lamp, the monitors pulling maybe 80W together, and the laptop on charge - I'm seeing maybe 150-180W draw at peak. The Fogstar battery has been brilliant so far, I'm rarely dropping below 80% SOC even on gloomy days, though we've had a decent spell of weather lately so December will be the real test.

What I'm scratching my head over is heating. I've got a small oil-filled radiator in there at the moment which is obviously a complete non-starter for solar - it's pulling 1000W and would flatten the battery in no time. Has anyone found a sensible solution for heating a small office space without wrecking their energy budget? Thinking maybe a 12V heated mat under the desk, or just biting the bullet and getting a small wood burner installed?

Nice one @Gazza82 — love the commitment to going properly off-grid rather than just running a cable!

What are you actually running in there? That'll make or break the system sizing conversation. A couple of monitors and a laptop is very different to a kettle and electric heater 😅

For a garden office I'd lean toward a decent Victron SmartSolar MPPT if you haven't already gone down that route — the Bluetooth monitoring alone is worth it when you're working in there and want a quick check on state of charge.

Winter months can be brutal on solar here in the UK too, worth factoring in some buffer capacity if you're relying on it year-round.

Sounds like you cut off mid-post though — what kit did you actually end up with?

@Gazza82 the garden office rabbit hole is a proper gateway drug to the wider off-grid world — I went narrowboat first, then ended up rewiring my mate's log cabin using almost identical principles.

One thing worth watching with a static setup like yours: battery temperature management matters more than people realise. Unlike my boat where I'm constantly moving and generating heat, a garden office battery bank can get seriously cold sitting idle through a British winter. If you've gone lithium (Fogstar cells are popular for good reason), make sure you've got low-temperature charge protection sorted or you'll damage the cells without ever knowing.

Also — what's your shading situation? A 6x4m cabin roof sounds promising but overhanging trees and neighbouring fences kill more garden solar setups than anything else. A Victron MPPT will at least squeeze every watt out of whatever you've got.

@Gazza82 done exactly this with my garden office — it's the setup that got me hooked tbh. Running a Victron SmartSolar MPPT with Fogstar Drift lithium batteries and haven't looked back.

One thing worth planning for early: winter output drops off a cliff in the UK. My panel yield in December is maybe 20% of what I get in July. Make sure you're not undersizing the battery bank based on summer testing.

Also worth thinking about what loads you're actually running — monitors and laptops are nothing, but if you want a small heater forget it, you'll need serious capacity or a backup solution like a small inverter genny for the cold months.

@RiverSoul narrowboat to garden office is an interesting journey in reverse to mine 😄