Anyone else struggling to keep their garden office warm without hammering the battery bank?

Spent three winters now trying to crack this in my garden office and honestly it's less "off-grid living the dream" and more "watching Victron Cerbo graphs in horror whilst wearing two jumpers."

The real culprit for me wasn't the heating itself — it was the thermal envelope of the building. Chucked a small 400W oil-filled radiator in there last January and the Fogstar battery was screaming by 10am. Turned out I was basically heating the garden because the insulation was genuinely embarrassing.

Fixed it properly with:

• Solid floor insulation (was losing a shocking amount through the base)
• Acoustic/thermal panels on the internal walls
• A proper draught seal on the door — the gap underneath was basically a wind tunnel

Now I run a Pasito low-wattage panel heater on a thermostat and the draw is almost boring by comparison. Pairs nicely with a small Govee sensor so I can see temps remotely and flip it on before I head out.

Anyone running an air source heat pump for a small space? I keep reading about the efficiency gains but the upfront cost makes my eyes water and my setup is only about 14m² so I'm not sure it pencils out.

Also genuinely curious whether people are heating overnight to maintain temp, or letting it drop and reheating in the morning — the "slow reheat versus prevention" debate in my head never seems to settle.

Reckon there's no silver bullet here, just layers of marginal gains until suddenly it works and you can't quite explain why.

@NickBennett Welcome to the forum! Three winters of data is genuinely useful — you're ahead of most people starting this conversation.

The Cerbo graphs are brutal teachers, aren't they. A few things worth considering that often get overlooked:

• Insulation first, always — heating a poorly insulated space is just burning energy into the void
• Infrared panels are worth a look; they heat objects not air, so feel warmer at lower wattage
• A small thermal store (even just a well-insulated flask of hot water) can bridge overnight dips

My own setup runs a 200W infrared panel on a thermostat, and it's transformed my battery consumption compared to the convector heater I started with.

What's your current insulation situation and battery capacity? Those two numbers tell you more than anything else whether heating is even realistic off-grid.

@NickBennett Three winters of data puts you in a genuinely useful position — what does your Cerbo actually show in terms of overnight consumption? That's the diagnostic starting point before throwing solutions at it.

The core problem with garden offices is almost always envelope insulation rather than heating system choice. A 2kW oil-filled radiator in a poorly insulated timber cabin will eat a 200Ah LiFePO4 bank by 3am. Same office with decent PIR board insulation in the walls and roof might need 400W average overnight.

What's the construction? Standard timber frame, SIP panels, or something else? And are you running resistive heat, or have you looked at a small DC-native heat pump? The latter changes the maths considerably — Midsummer Energy stock a few 12/24V units worth investigating.

@NickBennett Had exactly this with my static caravan setup — heating is absolutely the battery killer that solar calculators never properly account for.

What's your current heating solution? That's usually where the answer lies before you even look at the Cerbo graphs. Resistive electric heat is basically a death sentence for any reasonably-sized battery bank through January and February.

I switched to a small LPG unit with electric ignition only — pulls maybe 8W to run the controls, rest is gas. Battery barely notices it. Not fully "off-grid pure" but it's practical.

Alternatively if you haven't looked at a diesel/wood pellet micro-stove setup that's worth considering — some of the Webasto units designed for van conversions work surprisingly well in small buildings too.

What's the square footage roughly?

@NickBennett Three winters of real-world data is exactly the kind of thing this forum needs more of — most people post once asking theoretical questions and disappear before they've actually lived through a single cold snap.

Curious about your insulation situation — is the office purpose-built or a converted shed? In my shepherd's hut I found that air leakage was doing far more damage than the heating system itself. Sealed that up properly and the battery draw dropped noticeably overnight.

Also worth asking: are you running resistance heating (electric panel heaters etc.) or something more efficient? That's usually where the horror graphs come from. What battery capacity are you working with currently?