Victron's MultiPlus and Quattro are both inverter/chargers with built-in transfer switches, but the Quattro adds a crucial feature: two independent AC inputs. This guide explains when that second input justifies the significant price premium.
What's Different About the Quattro?
The Quattro is essentially a MultiPlus with an extra AC input and a larger transfer switch. Both devices invert, charge, and switch between AC sources. The key differences:
| Feature | MultiPlus | Quattro |
|---|---|---|
| AC inputs | 1 | 2 (with priority control) |
| Transfer switch | Single input | Dual input with automatic priority |
| Size range | 500VA – 5000VA | 3000VA – 15000VA |
| System voltages | 12V, 24V, 48V | 24V, 48V (no 12V models) |
| PowerAssist | Yes | Yes (both inputs) |
| Parallel operation | Up to 6 units | Up to 6 units |
| Three-phase | Yes | Yes |
| Price | From ~£200 | From ~£1,200 |
How Dual AC Inputs Work
The Quattro's two AC inputs have configurable priority. Typically:
- AC Input 1 (Priority) — connected to grid/shore power. This is the preferred source.
- AC Input 2 (Backup) — connected to a generator. Used only when AC Input 1 is unavailable.
The Quattro automatically switches between inputs. If shore power fails, it seamlessly transitions to the generator (if running). If neither input is available, it runs as an inverter from the battery. Each input has its own configurable current limit.
When You Need a Quattro
1. Grid Power Plus Generator Backup
The most common Quattro application. In off-grid homes with both a grid connection (or micro-grid) and a backup generator, the Quattro manages both automatically. Grid power is used when available, generator kicks in during outages or when batteries are low, and the inverter covers the gaps.
2. Marina Shore Power Plus Onboard Generator
Large sailing yachts and motor cruisers often have both shore power connections and an onboard generator. The Quattro connects to both — shore power when moored, generator when at sea or anchored. No manual switching required.
3. Two Different Shore Power Sources
Some installations (particularly larger boats with berths in different marinas, or sites with two utility connections) benefit from having two shore power inputs. The Quattro handles the switching and can draw from either source.
4. Large System Requirements
The Quattro range starts at 3000VA and goes up to 15000VA — it includes the largest single-unit inverter/chargers in the Victron range. If you need more than 5000VA from a single unit, the Quattro is your only option (aside from paralleling multiple MultiPlus units).
When You Don't Need a Quattro
Most installations only have one AC source at a time — either shore power, or a generator, but not both simultaneously wired in. In these cases, a MultiPlus or MultiPlus-II is sufficient and much more cost-effective.
Campervans and Motorhomes
Even if you have both hookup and a portable generator, you typically only use one at a time. A MultiPlus with a single AC input handles this fine — just plug in whichever source you're using.
Narrowboats
Most narrowboats have shore power or an engine-driven generator, but rarely both wired permanently. A MultiPlus is the standard choice. The Quattro only makes sense for larger boats with a permanently installed generator and regular shore power use.
Budget Considerations
The price gap between a MultiPlus and a Quattro is substantial — often £500–1,000 or more for equivalent power ratings. Unless you genuinely need dual AC inputs, this money is better spent on batteries, solar, or other system components.
What About the Quattro-II?
The Quattro-II is the newer version with grid-code compliance (G98/G99 in the UK) and ESS (Energy Storage System) support. It's designed for grid-connected home battery systems that also have generator backup. Currently available in 48V configurations (5000VA and 10000VA), it's aimed at larger residential and commercial installations.
Can You Add a Second Input to a MultiPlus Later?
No. The MultiPlus hardware has a single AC input. You cannot upgrade it to accept two inputs. If your needs change and you require dual AC inputs, you'll need to replace the MultiPlus with a Quattro.
However, you can use an external transfer switch before the MultiPlus to manually or automatically select between two AC sources. This is cheaper than a Quattro but adds complexity and another point of failure.
Quick Decision Guide
| Scenario | Recommendation |
|---|---|
| One AC source (hookup OR generator) | MultiPlus |
| Grid + permanent generator backup | Quattro |
| Shore power + onboard generator (marine) | Quattro |
| Need more than 5000VA single unit | Quattro |
| Grid-tied home battery + generator | Quattro-II |
| Budget-conscious build | MultiPlus (save £500+) |
Summary
The Quattro's dual AC input is a genuine necessity for systems with two permanent AC sources — typically grid plus generator, or shore power plus onboard generator. For the vast majority of campervan, motorhome, and single-input installations, a MultiPlus or MultiPlus-II does everything you need at a significantly lower price. Only buy a Quattro if you need its dual-input capability or require more than 5000VA from a single unit.
