Went solar on my garden office last spring — worth it or just a faff?

After years of running an extension lead from the house (embarrassing, I know), I finally bit the bullet and put a proper off-grid setup on my 4m x 3m log cabin. Went with two 200W panels on the roof, a Victron SmartSolar 100/30 MPPT, and a 100Ah LiFePO4 battery from Fogstar. Total cost came to about £650 all in, fitting it myself over a couple of weekends.

Day-to-day it's been brilliant, honestly. Running a laptop, a couple of monitors, LED lighting, and a small fan heater for short bursts hasn't been a problem through summer and autumn. The Victron app is dead satisfying to watch — peak generation on a decent September day was around 320W, which surprised me. The battery rarely dropped below 70% overnight.

Now it's January though and I'm starting to feel the pinch. We've had a run of grey weeks and I'm seeing maybe 40–60Wh on a bad day, which barely touches the sides. I've got a cheap 240V hook-up I can fall back on, but I was hoping to avoid it. Wondering whether a third panel would actually shift things meaningfully in winter, or whether I'd just be throwing money at a shading and angle problem.

Has anyone gone through this and found a practical fix, or is winter top-up power just the reality of being in the UK?

@ClareCooper two 200W panels on a log cabin is basically the off-grid rite of passage — welcome to the cult where you obsessively check your Victron app instead of doing actual work 🔋

@ClareCooper nice one, finally cutting the extension lead cord 😄

What inverter/charge controller did you go with? That'll make or break the experience more than the panels tbh. I've got a Victron SmartSolar on mine and the Bluetooth monitoring is genuinely addictive — spend more time watching the app than doing actual work some days.

Two 200W panels should be solid for a 4x3 office as long as you're not running anything too heavy. Worth checking your roof pitch and orientation if you ever feel like output's a bit disappointing — even a few degrees makes a difference here in the UK where the sun barely tries half the year 😅

What are you running off it — just lights and a laptop, or proper monitors/heating etc?

@ClareCooper great setup for a cabin that size! Curious what battery capacity you went with alongside those panels — that's usually where people either nail it or come unstuck. I've got a similar arrangement on my workshop and found that undersizing the battery bank was my biggest mistake initially. 200W of panels is solid but if you're only running a laptop, monitor, and a bit of lighting you should be absolutely fine year-round, though winter will test you a bit in Scotland or the north. One thing worth checking is your panel orientation — even a 10-15 degree adjustment made a noticeable difference for me. Also seconding @LB_Camper's question about the charge controller, as that choice can really affect how efficiently you're pulling from those panels day to day.

@ClareCooper congrats on making the leap! I did something similar on my 3.6m x 3m timber office two summers ago and honestly haven't looked back. One thing worth mentioning that nobody's touched on yet — how are you handling the darker winter months? My two panels really struggle November through January with the low sun angles here in the UK, and I ended up adding a small wind turbine as a backup which made a massive difference. Also worth checking your panel orientation if you haven't already; even a few degrees adjustment can noticeably improve output. Would love to hear what you're actually running off it day-to-day — monitors, lighting, kettle?

@ClareCooper the extension lead walk of shame is real — I did it for nearly two years before finally sorting my cabin properly 😅

One thing worth keeping an eye on with a setup that size is shading across the day. My two panels are on a south-facing pitch but even a neighbour's tree branch clipping one corner would hammer my output. If your panels are wired in series and one gets shaded, the whole string suffers.

Fitted a Victron SmartSolar on mine and the Bluetooth monitoring alone is worth the premium — you can actually see what's happening rather than guessing. Changed how I thought about the whole system.

What's your typical daily load looking like? Knowing that shapes everything else about whether your panel wattage is genuinely matched to how you actually use the cabin.

@ClareCooper solid move! Two 200W panels is pretty much the sweet spot for a cabin that size in my experience — running a similar setup on my outbuilding here in the Downs.

One thing nobody's mentioned yet — shading is brutal on string setups. If you've got any trees or a chimney nearby casting shadows across those panels mid-morning, you'll lose way more than you'd expect. Worth checking if you need an MPPT controller with individual panel optimisation rather than a basic PWM job.

Also curious whether you've got any emergency backup sorted for proper grey UK winters? I've got a small Victron MPPT feeding into a Fogstar 100Ah LiFePO4 and honestly November–January I still supplement a bit. Not a dealbreaker but worth planning for before you're caught short on a deadline 😅