Author: Shayne and Anna
Key Message: Living aboard in a marina doesn’t mean you’re tied to the shore power pedestal. This post details how we reconfigured our Victron MultiPlus inverter/charger on our catamaran Paikea to prioritize our solar and battery system, making shore power an automatic backup instead of the primary source. We walk through the two key advanced settings—AC Input Control and Prioritize Other Energy Sources—that allow the boat to operate in “island mode,” only drawing from the grid when heavy loads or low battery levels meet specific, user-defined thresholds. This practical setup reduces electricity costs, promotes better battery health, and fosters a more self-reliant boating mindset, effectively turning your vessel into an intelligent hybrid energy system.
Living aboard a boat in a marina doesn’t mean you have to be shackled to the shore power pedestal. For sailors with robust solar and battery systems, that AC cable should be a backup, not a primary lifeline—both for your wallet and for a more self-reliant, lower-impact lifestyle.
After receiving a marina electricity bill that prompted a rethink, we dove into our Victron system on Paikea, our Lock Crowther Catana 42s. The goal was simple: flip the default logic. We wanted our solar and batteries to be the primary power source, with shore power acting as an automatic, conditional backup for heavy loads or poor weather. Here’s how we configured our Victron MultiPlus inverter to make it happen.
The Problem: Shore Power as the Default
Out of the box, most inverter/chargers, including Victron’s, are configured for a traditional use case: shore power is primary. The inverter supplements it if needed, and the batteries are charged from AC. For a liveaboard with significant solar investment, this is backwards. It means you’re paying for grid power (often from fossil fuels) even while your panels are producing, and your battery bank is underutilised.
The Solution: Two Key Victron Settings
The magic lies within the advanced settings of the Victron configuration software (VE.Config or Victron Connect). You’ll need a MK3-USB interface and the installer password to access these. The two functions we used work in tandem:
1. AC Input Control (Conditional AC Input Connection)
This is the cornerstone. It changes the inverter’s default behaviour from “connected to shore power” to “island mode.” The inverter will only connect to shore power when specific conditions you set are met.
We configured ours with two primary triggers:
- Load-based Connection: The inverter will only connect to shore power if the AC load exceeds a set wattage (we used 800W) for a continuous duration (we set 10 seconds). This covers tools like vacuums, sanders, or power tools.
- Voltage-based Connection: It will also connect if the battery voltage drops below a threshold (we set 24.5V for our 24V system), safeguarding against deep discharge on cloudy days.
The result: For the majority of the day, running lights, computers, and the fridge, the boat runs purely on solar and battery. The shore power cable is live, but ignored. Only when a heavy load kicks in or batteries get low does it seamlessly blend in grid power.
2. Prioritise Other Energy Sources
This setting complements the first by managing how the charger part of the unit behaves. When enabled, it tells the inverter-charger to only use shore power to charge the batteries up to a “sustain” voltage (we set 26.0V), not to a full absorption. It then leaves the “top-up” charging to solar, wind, or hydro.
A handy sun/wind icon appears in the control interface (Victron Connect, GX devices), giving you a one-touch override to force a full shore-power charge if needed—perfect before a forecasted week of rain.
Real-World Test and Benefits
We tested it with a 900W vacuum cleaner. On startup, the inverter powered it from the batteries. After 10 seconds above the 800W threshold, we heard a relay click—the system seamlessly transferred the load to shore power. Turning the vacuum off, it immediately disconnected from the grid and returned to inverter mode.
The benefits are clear:
- Cost Reduction: Maximises use of your already-paid-for solar assets, reducing marina electricity bills.
- System Health: Regularly cycles your battery bank, which is healthier than keeping it perpetually at float from shore power.
- Independence & Mindset: Reinforces the self-sufficient, systems-aware mentality crucial for safe offshore sailing.
- Environmental: Reduces reliance on often carbon-intensive grid power.
Important Considerations & Trade-offs
- Know Your System: This setup assumes you have a correctly sized solar array and battery bank to handle your daily baseload. If not, you’ll constantly trigger the shore power connection, defeating the purpose.
- Battery Chemistry: The “Prioritise Other Energy Sources” function has nuances related to absorption intervals. While it worked flawlessly with our lithium system, those with lead-acid or AGM batteries should research further or consult an expert.
- It’s Not for Everyone: If you are in the marina short-term or running high-load appliances constantly (e.g., air conditioning, electric heating), the traditional setup may be more practical.
Final Thoughts
This configuration isn’t about rejecting shore power; it’s about demoting it to a strategic backup. It turns your boat into a true hybrid system, intelligently managing its energy resources. For liveaboards or those undertaking refits, it’s a logical step towards greater efficiency and independence.
The depth of configuration in professional systems like Victron is impressive. It rewards those willing to move beyond the default settings and tailor their electrical system to their actual sailing—and docked—life.
Have you configured your system for solar priority? What thresholds or settings have you found effective? Share your experiences or questions in our YB Forum on our Members Page.