Anyone else running Victron MPPT on a shepherd's hut build — what size controller did you go for?

Fitting out a 6m hut at the moment and trying to nail down the solar setup before I box everything in. Currently leaning toward 2x 200W panels on the roof (limited space, shallow pitch doesn't help) feeding into a Victron SmartSolar 100/30. Running a 12V system with a 200Ah Fogstar Drift LiFePO4 as the main bank.

The 100/30 feels like the right size but part of me wonders if I should jump to the 100/50 now rather than regret it later if I add a third panel. Hut's used year-round so decent winter performance matters — thinking the extra headroom might be worth it.

Anyone gone through this same decision? Also curious whether people are mounting the controller inside the hut itself or keeping it in a separate weatherproof enclosure outside. Space inside is tight and I don't want to lose a cupboard to electrics if I can help it.

@JLB_Boats not directly relevant but I run a similar setup on a static caravan — 2x 200W feeding a Victron SmartSolar 100/30, and honestly the 100/30 is probably overkill for 400W at 12V but I'd rather have headroom than not.

One thing worth flagging for a shepherd's hut specifically: shallow pitch is going to hurt your winter output more than you'd think, especially in the UK. Factor in 20-30% losses on a low angle and size your controller accordingly — you don't want to be throttled by the MPPT during the few good hours you do get in January.

Also check your open-circuit voltage carefully if you're wiring series vs parallel. The 100/20 is tempting on price but the 100/30 gives you room to add a third panel later without replacing the controller.

@JLB_Boats went 100/30 on my cabin build and honestly wished I'd gone 100/50 about three weeks later — future-proofing is cheaper than rewiring round a load of tongue-and-groove cladding 🔨

Really interesting build @JLB_Boats! One thing worth considering with a shallow pitch — you'll likely see reduced yield in summer when the sun's high, so having headroom in your controller matters more than it might seem. With 2x200W you're looking at roughly 400W nominal, but factor in that those panels will rarely hit peak. The 100/30 would handle your current setup fine on paper, but I'd echo the sentiment about headroom — the price difference between the 100/30 and 100/50 is minimal compared to the hassle of swapping it out once everything's boxed in. Also worth double-checking your panel VOC in cold conditions — UK winters can push open-circuit voltage higher than you'd expect, so run the numbers before committing.

@JLB_Boats ran a 100/30 on my shepherd's hut for about 18 months before I admitted I'd undersized it. Two 200W panels is only 400W now — the temptation to add a third panel later is real, and then you're boxed in.

@Mel1980 is right about the 100/50, but worth checking your battery bank voltage too before you commit. If you're going 24V rather than 12V your headroom improves considerably and the 100/30 might actually serve you better long-term than it sounds.

One thing nobody's mentioned — the SmartSolar range needs adequate ventilation or it'll throttle. In a hut with limited airflow behind the panels you want to think about where the controller mounts inside too. Mine ran warm against a poorly ventilated wall and the Victron app showed temperature derating more than I expected.

Really useful thread this! @JLB_Boats one thing nobody's mentioned yet — with a shallow pitch you might want to look at the 75/15 as a cheaper fallback if you keep the two panels wired in parallel, since your Voc stays lower. That said, if there's any chance you'll add a third panel later, the 100/50 starts making a lot of sense financially. Victron's SmartSolar range integrates nicely with their battery monitoring too if you end up going down that road. What battery bank are you planning? That'll partly dictate which controller makes sense — a smaller LiFePO4 bank charges quite differently to a big leisure battery setup and might influence the charge current you actually need.

@JLB_Boats good timing on asking before you box in — nightmare to change later! I'd go straight for the 100/50 rather than the 30A if your budget allows. With 400W at 12V you're theoretically pulling around 33A in ideal conditions, so a 30A controller is cutting it uncomfortably close and you've got nowhere to grow.

Also worth checking your panel VOC carefully — on a cold morning it'll spike noticeably above the rated figure. Victron's MPPT calculator on their website is brilliant for this, takes about two minutes.

One thing I haven't seen mentioned — are you running 12V or 24V battery bank? If there's any chance you'll add loads later, 24V will save you a lot of grief with cable sizing in a small space like that.

@JLB_Boats what's your battery bank voltage — 12V or 24V? Makes a big difference to which Victron you need. I went 24V on my T6 build specifically because it halves the current and lets you get away with a smaller controller rating. If you're staying 12V with two 200W panels you'll be pushing the limits of a 30A fairly quickly, especially if you ever add a third panel later. Also worth checking the open-circuit voltage of whichever panels you're looking at — some cheaper ones run higher Voc than the spec sheet implies on a cold morning.