An inverter supplies AC from the battery; an inverter-charger adds charging and usually source-transfer functions whose exact behaviour must be checked.
An inverter converts 12V battery power to 230V AC. An inverter-charger does that — and also charges your leisure battery from mains when hook-up is available. Here is how to decide which one your build needs.
What each device does
Standalone inverter: Converts 12V DC from your leisure battery to 230V AC. One-directional. When you plug into hook-up, the inverter does nothing — it is bypassed or off. You need a separate battery charger to top up from mains.
Inverter-charger (combi): Does both. In inverter mode it runs your appliances from battery. In charging mode it takes mains power and charges your leisure battery. High-end models (Victron MultiPlus) add a third function: automatic transfer switching — it detects when hook-up is connected and seamlessly switches your van's 230V circuits to mains power, bypassing the battery. Simultaneously, it charges the battery from mains.
The key advantage of an inverter-charger
With a separate inverter and separate battery charger, you have two components, two sets of DC cables, and manual management of which is running.
With an inverter-charger:
- Connect to hook-up → battery charges and appliances run on mains automatically
- Disconnect from hook-up → inverter kicks in from battery seamlessly
- One unit. One installation. Cleaner wiring.
When a standalone inverter is the right choice
You rarely or never use mains hook-up. If you free camp 95% of the time and only occasionally need a hook-up charging point, a standalone inverter plus a simple mains charger is a lower-cost, simpler solution.
You want to keep cost down. A Victron Phoenix 12/800 (standalone inverter) costs around £240. The equivalent Victron MultiPlus-II 12/800 (inverter-charger) costs around £600. If the charger function is rarely used, that £360 extra is hard to justify.
You have a simple build. Fewer components means fewer potential failure points.
When an inverter-charger makes sense
You use hook-up regularly. At campsites, festivals, stopovers, or any location with EHU, the inverter-charger handles switching automatically with no manual intervention.
You want seamless integration. The Victron MultiPlus range integrates with the Victron ecosystem (SmartSolar, SmartShunt, Cerbo GX) for full system monitoring and optimised charging. See our Victron MultiPlus for Campervans: Design and Sizing for details.
You want to power high-draw appliances from hook-up without running your battery down. With a MultiPlus, mains power feeds your appliances directly while simultaneously charging the battery — you never drain your battery on a hook-up pitching.
Your build is complex. Motorhomes, full-time van conversions, and builds with multiple charging sources benefit from the integration and automation of an inverter-charger.
The Victron MultiPlus: the standard UK choice
The Victron MultiPlus-II is the dominant inverter-charger in UK campervan builds. Key specs:
| Model | Continuous AC output | Charge current | UK price (approx) |
|---|---|---|---|
| MultiPlus-II 12/800 | 650W | 35A | ~£600 |
| MultiPlus-II 12/1600 | 1,300W | 70A | ~£750 |
| MultiPlus-II 12/3000 | 2,400W | 120A | ~£1,000 |
The MultiPlus also includes:
- PowerAssist: Supplements mains power with battery power to run loads exceeding the hook-up supply (e.g., run a 2,000W appliance on a 6A/1,380W hook-up by drawing the difference from battery)
- Full VE.Bus integration with Cerbo GX for monitoring via the Victron VRM portal
See our Victron MultiPlus for Campervans: Design and Sizing for wiring and installation details.
Can you add a mains charger alongside a standalone inverter?
Yes. A Victron Blue Smart IP22 charger (£80–£130) connected to the battery gives you mains charging capability. Combined with a Phoenix inverter, this gives you roughly the same functionality as a MultiPlus at similar total cost — but as two separate units rather than one integrated device.
The integrated approach wins on space, wiring simplicity, and the automatic transfer switch function. The two-component approach wins if you already own one of the components or need a specific inverter size not available in the combi format.
Worked planning check
If you only need a small occasional AC load, compare a standalone inverter and separate mains charger with an integrated unit. Include transfer equipment and AC protection in both designs. A cheaper inverter alone is not equivalent to a complete inverter-charger installation.
The figures or dimensions in this example are explicit planning assumptions, not a product test or an installation specification. Replace them with your equipment data and actual measurements.
Planning questions
How do I calculate inverter battery current?
Divide AC watts by assumed inverter efficiency and loaded battery voltage. Add other DC loads, and check starting surge separately. Use the result as a design input rather than a fuse recommendation.
Does an inverter use power with nothing plugged in?
Usually it has an idle consumption; check the exact model and operating mode. Multiply idle watts by hours switched on to include it in the daily energy budget.
Can any lithium battery run a large inverter?
No. Check BMS continuous and short-duration current, battery voltage, cable, protection and terminals. Energy capacity alone does not establish output capability.
Summary
| Standalone inverter | Inverter-charger | |
|---|---|---|
| Converts battery to 230V | ✓ | ✓ |
| Charges battery from mains | ✗ (need separate charger) | ✓ |
| Automatic transfer switching | ✗ | ✓ |
| Lower cost | ✓ | ✗ |
| Simpler wiring | ✓ | ✗ (more complex but cleaner) |
| Victron ecosystem integration | Limited (VE.Direct only) | Full (VE.Bus) |
FAQ
Is a Victron MultiPlus worth the cost for a campervan?
For full-time van lifers or anyone who regularly uses hook-up, yes. For occasional or off-grid-only builds, the standalone inverter + separate charger is better value.
Can I use a 3,000W inverter-charger on a standard 16A hook-up?
The hook-up supply is limited to 16A × 230V ≈ 3,680W. A 3,000W inverter-charger can run appliances up to the hook-up limit while charging the battery from remaining capacity. The MultiPlus's PowerAssist feature can even supplement the hook-up with battery power for short-duration loads exceeding the hook-up supply.
Do I still need a solar controller with an inverter-charger?
Yes. The inverter-charger handles battery charging from mains only. Solar panels still need an MPPT solar charge controller connected to the battery. The Victron ecosystem allows the SmartSolar MPPT and MultiPlus to coordinate via Cerbo GX.
Related
- Campervan inverter guide
- Hardwired vs Plug-In Inverter for a Campervan: Which Is Better?
- Low-Frequency vs High-Frequency Inverters for Campervans
- Pure Sine Wave vs Modified Sine Wave Inverter for Campervans
- Best Campervan Inverter: Size, Surge and Standby
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Jack Kennedy is a self-builder who has built two vans. He created Roam Wired to simplify conversion planning and share free tools, supported by affiliate links.
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