Multiple small MPPTs vs one large MPPT — wiring & sizing

Been mulling this one over for the shepherd's hut build and thought it worth opening up for discussion here.

My current setup on the cabin uses a single Victron SmartSolar 100/30, which works fine — but the panels are on a clean south-facing roof with virtually no shading. For the hut, though, I've got a more awkward site with a tree line that clips the array from mid-afternoon onwards.

So I'm seriously considering splitting into two or three smaller MPPTs rather than one larger unit. The logic being: if one string is in partial shade, it's only dragging down its own controller, not the whole array. Each MPPT hunts for its own optimum independently.

The bit I'm getting my head around is the wiring overhead. Three Victron 75/15s versus one 150/45, for example — you're running more DC cable runs, more fusing points, more connections into the busbar. More potential failure points, arguably, though each failure is also less catastrophic.

Cost-wise in the UK it's not always a massive difference once you factor in Fogstar or Bimble for bits, but it's not nothing either.

A few things I'd genuinely like to hear thoughts on:

• At what point does splitting arrays actually make measurable difference to real-world yield?
• Does anyone use Victron's VE.Smart networking to coordinate multiple smaller units effectively?
• Any gotchas with mixed-orientation strings on separate MPPTs?

Curious whether anyone's done a side-by-side comparison with datalogging, even informal. Gut feelings welcome too — sometimes experience beats theory on this stuff.

Great topic @WingAndPrayer! One thing worth considering beyond the obvious redundancy argument is string voltage flexibility. With multiple smaller MPPTs you can configure each string independently — so if you've got panels on different roof pitches or orientations on the shepherd's hut, each controller tracks its own peak without the others dragging it down. That's a genuine efficiency gain rather than just theoretical.

The wiring also stays tidier in my experience — shorter home runs from each array section to its own controller rather than everything converging at one point.

Downside is obviously cost per watt of capacity, and you're doubling up on monitoring overhead unless they're all on the same VE.Network or similar. What panel layout are you thinking for the hut? That'd probably determine which approach makes more sense practically.

Good timing on this thread — just went through this exact decision for my van build.

Ended up running two smaller MPPTs rather than one big unit. Main practical reason nobody's mentioned yet: shading. If your panels are on different roof pitches or orientations (very likely on a shepherd's hut), separate controllers mean partial shading on one string doesn't drag down the other.

Also worth noting the wiring runs — two shorter DC cable runs to two controllers often beats one long run to a centralised unit. Voltage drop adds up fast.

Went Victron for both mine, kept the same comms ecosystem which made the Cerbo integration dead simple.

The cost argument against is real though — two Victron units isn't cheap. Might be worth pricing up a Renogy dual-tracker if budget's tight, @WingAndPrayer.

Been through exactly this decision for my shepherd's hut, so useful thread.

One thing nobody's mentioned yet — partial shading scenarios are where multiple controllers really earn their keep. My hut has panels split across two roof pitches with different orientations. Running them into a single MPPT would've been a nightmare; separate Victron SmartSolar 75/15s on each array means each string tracks its own MPP independently.

Also worth considering cable runs. With a small hut, keeping each array close to its own controller rather than routing everything to one central unit can save a fair bit of copper and reduce voltage drop headaches.

The cost argument usually favours one large unit on paper, but once you factor in your actual roof geometry and shading, the maths can flip pretty quickly.

Ran two Victron 75/15s on my shepherd's hut rather than one bigger unit — mainly because my panels are split across two roof pitches facing different directions.

The east/west split means they're rarely peaking at the same time anyway, so a single MPPT would've been compromised chasing two different curves simultaneously. Separate controllers let each string do its own thing.

Wiring was actually simpler than I expected — two clean runs straight into the battery rather than one complicated combiner situation.

Only downside is two lots of monitoring in the Victron Connect app, though you can link them via VE.Smart networking so they at least share battery voltage data properly. Worth doing if you go that route.

Really interesting thread — just what I needed to read actually, as I'm trying to figure out the same thing for my narrowboat setup where I've got panels split across the cabin roof and the cratch cover at odd angles to each other.

Quick question for @WillWebb and @GrumpyWanderer — when you're running two separate MPPTs like that, are you feeding them both into the same battery bank simultaneously? And does the Victron ecosystem handle that cleanly via VE.Direct without them "fighting" each other over charge state?

Also wondering whether two smaller units gives you better redundancy — if one controller packs in, you're not completely dead in the water (quite literally in my case 😅). Has anyone actually experienced a controller failure and been glad they had a backup running in parallel?