The Victron SmartSolar MPPT 75/15, 100/20, and 100/30 are the three most popular charge controllers for small solar systems — campervans, caravans, small boats, and garden sheds. They're compact, affordable, and handle the solar arrays most DIY builders install. But which one do you actually need? This guide compares all three side by side.
Specifications at a Glance
| Specification | MPPT 75/15 | MPPT 100/20 | MPPT 100/30 |
|---|---|---|---|
| Max PV voltage (Voc) | 75V | 100V | 100V |
| Max charge current | 15A | 20A | 30A |
| Max solar at 12V | 220W | 290W | 440W |
| Max solar at 24V | 440W | 580W | 880W |
| Load output | 15A | 20A | No |
| VE.Direct port | Yes | Yes | Yes |
| Bluetooth | Yes (SmartSolar) | Yes (SmartSolar) | Yes (SmartSolar) |
| Peak efficiency | 98% | 98% | 98% |
| Operating temp range | -30°C to +60°C | -30°C to +60°C | -30°C to +60°C |
| Weight | 0.5 kg | 0.5 kg | 1.3 kg |
| Dimensions (H×W×D) | 100×113×40mm | 100×113×40mm | 130×186×52mm |
Maximum Solar Capacity
This is the main practical difference. On a 12V battery system:
- 75/15 — handles up to 220W of solar. That's one 200W panel or two 100W panels.
- 100/20 — handles up to 290W. A single 200W panel with room to spare, but not quite enough for two 200W panels.
- 100/30 — handles up to 440W. Two 200W panels comfortably, or one 400W panel.
For most UK campervan builds with two 200W panels (the most popular configuration), only the 100/30 has enough capacity.
Physical Size
The 75/15 and 100/20 share the same compact casing — just 100 × 113 × 40mm and 0.5 kg. They tuck away easily in a campervan electrical cupboard.
The 100/30 is noticeably larger at 130 × 186 × 52mm and 1.3 kg — more than twice the size and weight. Still manageable, but plan your mounting space accordingly.
Load Output
The 75/15 and 100/20 include a load output terminal that can power small DC loads directly (rated at 15A and 20A respectively). This is useful for simple installations like a garden shed or boat where you want the MPPT to disconnect loads when the battery is low.
The 100/30 does not have a load output. In most campervan and boat builds, loads connect to the battery via a separate fuse box anyway, so the load output is rarely missed.
PV Voltage Handling
The 75/15 accepts a maximum of 75V from the panels. The 100/20 and 100/30 both accept up to 100V. This matters when wiring panels in series:
- Two panels in series with Voc of 22V each = 44V → all three controllers handle this fine.
- Three panels in series with Voc of 22V each = 66V → too close to the 75V limit after cold correction. The 100V controllers handle this safely.
- Two panels with Voc of 40V each = 80V → exceeds the 75/15, fine for the 100V models.
Which One Should You Buy?
Choose the 75/15 if:
- You have a single solar panel up to 200W
- You want the smallest, lightest controller
- You need the built-in load output
- Budget is the primary concern
Typical setup: 1 × 100W or 1 × 200W panel on a caravan or small boat.
Choose the 100/20 if:
- You have a single 200W+ panel and want headroom
- You need the load output but also want 100V PV input capability
- You might add a second small panel later
Typical setup: 1 × 200W panel with plans for a second smaller panel.
Choose the 100/30 if:
- You have two or more panels totalling up to 400W
- You're building a typical campervan or motorhome solar system
- You don't need the load output (most builds don't)
- You want the most popular, best-supported small MPPT
Typical setup: 2 × 200W panels on a campervan roof — the UK's most common DIY solar setup.
Price Comparison
The price steps between these three models are relatively small — typically £15–30 between each size. Given that, our advice is to buy the controller that matches your panels now plus your likely expansion within the next year. The 100/30 is the sweet spot for most builds, and its marginal extra cost over the 100/20 is well worth the doubled solar capacity.
Can You Upgrade Later?
Yes. All three models use the same wiring pattern (PV+, PV-, BAT+, BAT-) and the same VE.Direct port. Swapping a 75/15 for a 100/30 means disconnecting four wires and reconnecting them to the new unit. No other changes needed.
Our Recommendation
For the vast majority of campervan and small boat builds in the UK, the SmartSolar MPPT 100/30 is the right choice. It handles the most popular 2 × 200W panel configuration, costs only slightly more than the smaller models, and gives you room to grow. The 75/15 makes sense only for genuinely small single-panel setups where every pound and every gram matters.
