Anyone else running a garden office purely on solar + batteries through winter?

Mine's a 6x4m insulated timber cabin I use as a daily workspace. Running a Victron 100/30 MPPT, two Fogstar Drift 100Ah lithium batteries, and a 400W panel array facing south-ish (slight SW lean unfortunately).

Summer was fine — barely touched the batteries most days. But now we're into the short days I'm getting a bit nervous. Heating is a small oil-filled rad on low, plus laptop, monitor, a bit of lighting. Rough estimate puts me at 800Wh–1kWh/day draw on heavy use days.

Anyone actually tracked their winter generation vs consumption figures for something similar? Wondering if I need to add another panel or just accept I'll be topping up from the house feed occasionally.

DerekYoung76 | 847 posts

@Rodney similar setup here, though I've got a slightly larger array at 600W which genuinely made a difference through December and January. The honest truth is those shorter days will humble you pretty quickly - I found myself rationing the monitor brightness and ditching the kettle entirely by mid-January!

One thing worth mentioning that nobody talks about enough: panel angle. I tilted mine steeper for winter, closer to 60°, and picked up a noticeable improvement in those low-sun hours. Worth doing if your mounting allows it.

What's your actual consumption like on a working day? Laptop, monitors, lighting? That'll determine whether 400W sees you through or whether you're borrowing from the grid more than you'd like. The Fogstar batteries are decent kit, mind you - solid choice.

GafferTapeKing3 | 312 posts

@Rodney I've been running a similar setup since last October - the honest truth is December and January will humble you. Even with a south-facing array you're looking at maybe 1-2 usable hours of decent generation on a grey day up here.

Few things that genuinely helped me: a small propane heater taking the heating load completely off the electrics (game changer), and being brutal about what's actually plugged in. Laptop, LED lighting, a small monitor - fine. Electric kettle, fan heater, anything with a heating element - absolutely not.

Also worth checking your battery temp compensation settings on the Victron if you haven't - lithium performance drops noticeably in an unheated cabin overnight. The Fogstar Drifts should handle it but charging behaviour needs adjusting.

What's your actual daily consumption looking like? That's usually where the surprises hide.

MidlandsCamper | 1,204 posts

Worth flagging something nobody's mentioned yet — panel orientation matters enormously in December. My cabin array is 15° off true south and I lose a measurable chunk of generation compared to my neighbour's dead-south setup.

Also, @Rodney, your Victron MPPT will give you proper historical data via the VictronConnect app — check your actual daily yield figures from last November/December rather than relying on calculators. I was genuinely surprised how far below PVGis estimates I was sitting once you factor in fog, low-angle shading, and panel soiling.

One thing that transformed my winter situation: a small Govee temperature logger inside helped me correlate heating load (I use a 400W oil-filled rad on a thermostat) against battery state. Once I understood when I was drawing heavily, I could schedule heavy CPU tasks like video rendering to coincide with any decent midday generation window.

Squib | 23 posts

Not a garden office but my motorhome setup goes through similar winter struggles so I reckon the principles are the same. One thing I've been wondering — does anyone run a small propane or diesel heater for the really grim December/January weeks just to take the heating load completely off the battery bank? Seems like keeping the panels working purely for lighting, devices and a 12V fridge would make the whole system much more viable. @Rodney what's actually pulling the most from your batteries — is it heating, or the workspace gear like monitors and laptop chargers?

LazyFisher | 847 posts

Running my narrowboat through winter on solar is basically an annual exercise in managed disappointment — but the trick nobody mentions is a small propane heater taking the thermal load off your batteries entirely, because asking lithium cells to both heat the space and run your monitors in January is how you end up working in a café.