Anyone else struggling to heat their garden office without the bills going through the roof?

Swapped to a small Victron setup with a decent battery bank last winter and now my garden office is heated for roughly the cost of my neighbour's guilt about his energy bills.

The trick that actually moved the needle for me was insulation first, heating second — sounds obvious but most people do it backwards. I chucked some proper insulated panels on the walls before touching the heating setup and the difference was almost embarrassing.

Currently running a small infrared panel heater off my solar array rather than a convection heater, and it's a genuine game-changer for a tiny space. Infrared warms you not the air, so you're not constantly fighting heat loss every time the door opens. My Fogstar batteries handle overnight storage well enough that I'm rarely drawing from the grid before 9am even in December.

Few things worth considering if you're still on grid for heating:

• Thermal mass inside the office helps a lot (even just a few heavy shelves of stuff)
• A draught excluder on the door is embarrassingly effective
• Programmable heating so it's warm when you arrive, not heating an empty box all morning

What's the actual construction of your office — is it a standard timber frame? That makes a big difference to what's worth doing next. Some of those flat-pack garden offices are basically fancy sheds with the insulation values to match.

Curious whether anyone's gone down the air source heat pump route for a smaller outbuilding — seems like overkill but I'd love to be proved wrong.

Derek1977 | 847 posts | ⚡ Off-grid enthusiast

@SolarKeith don't leave us hanging mate, what's the trick! 😄

I'll add my twopenn'orth whilst we wait - biggest game changer for me was pairing a decent IR panel with a small thermostat controller rather than running convection heaters. IR warms you and the fabric of the building rather than just the air, so when the door opens you're not losing everything immediately. My 600W panel draws far less from the battery bank than the 2kW oil-filled radiator I was using before.

Also worth checking your insulation first before throwing any heating solution at it. I lost a whole weekend relaying the floor insulation in mine and the difference was remarkable - dropped my heating requirement by almost half overnight.

What size battery bank are you running Keith?

CornishBoater | 203 posts | ⛵ Boats & Shepherd's Huts

@SolarKeith yes please finish that sentence, the suspense is killing me! 😅

Genuinely curious whether you're running any kind of heat pump or just straight resistance heating off the battery bank? I've been wrestling with the same question for my shepherd's hut — resistance heating feels like such a waste of stored energy but the small 12V heat pumps I've seen seem a bit... optimistic in their efficiency claims.

What size battery bank are you running, and are you topping up overnight from grid at all? I'm wondering if a hybrid approach might be the sweet spot for cloudy UK winters where solar alone just isn't cutting it.

FETFan | 1,284 posts | 🚐 Vans & Narrowboats

@SolarKeith has clearly discovered the ancient art of the cliffhanger post — presumably his Victron MPPT cut out mid-sentence and he's still waiting for the sun to come back.

Meanwhile I'll guess: thermal mass + a well-sized Fogstar battery bank + a low-wattage panel heater on a smart timer — because that's exactly what I did in my shepherd's hut and my electricity bill went from "crying in Aldi" to "mildly smug in Waitrose."

The real trick most people miss is not reaching for a 2kW fan heater — a 400W panel heater running consistently murders a 2kW beast on efficiency.

@Derek1977 @CornishBoater don't hold your breath though, he might be on a narrowboat with 4G that drops every third word 😄

EcoFlowMaster | 312 posts | 🏠 Motorhome & Tiny House

@SolarKeith mate I've been sitting here refreshing this thread like it's a Fogstar Black Friday sale. My tiny house setup runs a similar Victron system and I've been throwing money at insulation trying to solve what

ZFS_OffGrid | 847 posts | 🚐 Motorhome & Static Caravan

@SolarKeith classic. Three people having a breakdown over an unfinished sentence and you've vanished.

Anyway — garden office heating with solar is dead doable but the battery sizing is where most people cock it up. You need more capacity than you think for the dark months. Running a small infrared panel off a Fogstar Drift 12V setup in my static worked surprisingly well last winter. Less draw than you'd expect.

The real trick (since Keith's clearly gone for a brew) is thermal mass + insulation first, then size the system around what's left. Don't just chuck panels at a poorly insulated shed and wonder why the batteries die by 3pm in November.