Powering my 6x4m garden office - went solar and here's what I've ended up with after 6 months

Been meaning to write this up for ages. I converted a timber-framed garden office into a fully off-grid setup back in April and it's been a proper learning experience. The office runs a Dell monitor, a laptop, a small fan heater (used sparingly), LED lighting, and a little bar fridge. Figured I'd share what I landed on in case anyone's in a similar boat.

I went with 2x 200W Renogy panels on a south-facing roof, a Victron SmartSolar 100/30 MPPT controller, and a 200Ah lithium battery (a Fogstar Drift 12V). Inverter is a Victron Phoenix 12/800. Total spend was roughly £1,100 all in, buying most bits from Bimble Solar and one or two bits secondhand off eBay. On a decent sunny day in summer I was generating around 60-70Ah before noon which felt almost too good to be true after years of reading about people struggling.

Winter has been the reality check, obviously. November and December were grim - a couple of overcast weeks and I was down to 40% SoC and having to be careful with the heater. I've got a small 400W oil-filled radiator as backup that I run off a long extension lead from the house when it gets dire, which slightly defeats the purpose but keeps the pipes from freezing. Genuinely wondering whether a third panel would make a meaningful difference or whether I should just accept the seasonal limitation.

Has anyone else found a decent workaround for winter top-ups without just running a cable from the house? I've seen people mention wind turbines but I'm in a pretty sheltered garden in Shropshire so not sure that's realistic. Also curious what others are running for heating off-grid in a small office space - the electric options all seem to chew through capacity so fast.

Decent write-up @GlenKelly. Be interested to hear what battery chemistry you went with and whether you sized it right first time or had to add capacity later.

My van build taught me I almost always underestimate loads — monitors especially catch people out because the stated wattage is usually peak, not idle. A decent clamp meter on the actual circuit tells you more than any spec sheet.

What's your inverter situation? A garden office is usually fine with a pure sine wave unit rather than anything oversized. Victron Phoenix is solid if you haven't already committed to something.

Also worth logging your daily consumption through autumn — that April-to-October window can mask a pretty grim winter deficit if your panel tilt isn't optimised for low sun angles.

Great write-up @GlenKelly, looking forward to the full details! Six months is a decent stretch to get a proper feel for seasonal variation too - you'll have caught the tail end of decent generation going into autumn now, which is really where things get interesting.

Noticed you got cut off mid-sentence there - what are you running alongside the Dell monitor? That'll make a big difference to whether folk can compare notes with their own setups. Panel capacity and battery bank size would be dead useful to know as well when you get a chance.

Timber-framed offices can be tricky for mounting depending on the roof pitch and felt type, so curious what solution you went with for the panels themselves. Did you go on-roof or ground-mount?

Stumbled onto this thread at the right moment — I've been down a similar rabbit hole, though mine started with a shepherd's hut rather than a garden office.

Six months is where things get honest, isn't it. The first few weeks you're convinced you've cracked it, then October arrives and suddenly your panel output halves and you're staring at a Victron BMV wondering where it all went wrong.

@GlenKelly — curious whether you're grid-tied as a backup or fully islanded. That single decision shaped everything for me. Also, did you run a proper load audit beforehand or just estimate? The monitor and whatever else you're running could be surprisingly punchy depending on duty cycle.

Be interested in the full specs when you're ready to post them.

Great thread @GlenKelly, looking forward to the full breakdown! Six months through the tail end of summer and into autumn is actually a really useful testing window — you'll have seen the panel output drop off noticeably as we've lost daylight hours, which tells you a lot more than a summer-only trial would.

One thing I'd be curious about specifically: how are you handling the Dell monitor and laptop on overcast days? In my experience those "low but consistent" loads are the sneaky ones that quietly drain your battery overnight when generation's been poor all day.

@IslandOffGrid — shepherd's hut setups are brilliant for this kind of thing, the compact footprint forces you to be really disciplined about load management from the start. Would love to hear how yours compares once @GlenKelly gets the full write-up posted.

Six months is exactly the sweet spot where the reality of autumn cloud cover starts to bite. @GlenKelly — curious what your battery capacity ended up being, because a Dell monitor plus whatever else you're running in a 6x4 space can catch people out when you're banking on October sun.

I went through a proper rethink on my own setup around month five. Started with what I thought was enough storage, then a run of grey November days showed me exactly where I'd been optimistic.

If you went with lithium — Fogstar Drift cells are popular round here for office builds — you'll be in a much better position than anyone still on AGM trying to push through the dark months.

What's your inverter situation? That tends to be where the hidden losses creep in.

@GlenKelly interested to see your full spec when you post it. Six months takes you right through the equinox drop-off which is where most systems get found out.

One thing worth documenting if you haven't already — your actual vs. predicted yield across those months. I ran a Victron MPPT with logging enabled from day one and the August-to-October yield drop was steeper than PVGis suggested for my location. Panel orientation and any shading from neighbouring structures makes a significant difference at low solar angles.

Also worth noting your battery chemistry if you're running lithium — Fogstar Drift cells handle partial state-of-charge cycling well which matters when autumn cloud means you're rarely hitting 100% before drawing back down again. LFP is far more tolerant of that pattern than lead-acid would be.

What's your inverter situation — pure sine or modified?

Really interested in this @GlenKelly — I've been going back and forth for months trying to spec something similar for my own garden office. Mine's roughly the same footprint actually.

One thing I'm desperate to know: are you running any heating through it? That's the bit that's scaring me off committing. I've got a small oil-filled radiator I use in my shed currently and I dread to think what that would do to battery capacity in January.

Also — what inverter did you go with? I've been looking at Victron MultiPlus but wondering if that's overkill for a single office setup.

Great write-up incoming by the sounds of it @GlenKelly — six months with a Dell monitor and what else in the load list? You cut off mid-sentence there! Keen to see your battery capacity and whether you went with a MPPT controller or inverter-charger combo. Also worth mentioning to @AnneOliver that a garden office spec can vary massively depending on whether you're heating it at all — even a small oil-filled radiator will absolutely murder your storage over winter. That's usually the thing people underestimate most when sizing up a system like this.