Onboard Electricity Basics & FAQ | Modern Sailing

Onboard Electricity Basics & FAQ

Boat Electricity Basics

Want to keep your mobile devices charged or use a small appliance away from shore? If your bareboat charter plans include being away from the dock for more than a few hours, beforehand, it's a good idea to understand your boat's electrical system and how to properly utiitize it. 

MSC boats are equipped with two types of electrical power systems onboard.

1) The 12 volt DC system is electrical current supplied directly from the house batteries (direct current = DC).

  • Critical onboard systems such as navigation lights, cabin lights, and bilge pumps are wired to the 12 volt DC system.
  • You can access 12v DC power through the round “cigarette lighter” outlets, which are often located near the chart table.
  • 12v USB charging ports can also be found on some MSC boats, typically in the Gold, Platinum, and Catamaran Fleets.

An example of a 12v outlet on a main electrical control panel.


A 12v USB port for charging USB devices aboard Wimm.

2) The 110 or 120 volt AC system is alternating current that comes from a connection to shore power or from an onboard power inverter.

  • Inverters draw 12v DC electricity from the house batteries and convert it to alternating current. This enables the electrical system to power small electronics and appliances such as laptops and coffee makers.
  • Connect to the 110 or 120v AC system via the standard house electrical outlets.
  • Not all MSC boats come equipped with an inverter. Depending on the inverter, there are limits on how many watts of power an inverter can supply.

A standard 110v power outlet on a boat. This only will be electrified only when the boat is connected to shore power or when the inverter is running.

This outlet pair combines 110v AC and 12v DC outlets.

Below, we've compiled a list of common questions we've encountered from bareboat newcomers.

How do I use the inverter on my boat?

  • Disconnect from shore power, if connected.
  • Locate the AC system selector switch, if your boat has one, and ensure it's switched on.
  • Locate the inverter's power switch to turn it on. In some cases, the power switch will be on the main electrical control panel. Some inverters have their own power switch built into them.
  • If in doubt as to the location of switches, check the boat's white binder or ask an MSC fleet technician for assistance.
  • Be sure to power off the inverter when the house outlets are not in use. The inverter will draw power from the batteries even when there is nothing plugged into the outlets.
  • Use caution when operating small appliances to avoid draining the batteries or overloading the inverter. Any device that draws more than 800 watts is likely to overload and possibly damage the system. High wattage appliances such as hair dryers and microwaves cannot be used away from shore power.

An example of an inverter switch. As you can see, our fleet techs do a great job of labelling them so they aren't too difficult to find.

This inverter switch is located next to the house and engine battery switches.

How can I prevent battery drainage or damage?

To learn more about smart onboard power management and preventing battery drainage, see our article Marine Battery and Power Management Basics.

Which MSC boats have inverters?

Some boats in the MSC fleet do not have inverters and supply only 12v DC power when disconnected from shore power. If access to 110/120v AC electricity during your time away from shore matters to you, see the article Choosing the Right Boat for Your Charter and check the fleet spreadsheet to see how boats are equipped. 

MSC has one portable inverter that charterers can borrow for boats that do not come equipped with an inverter. Please call or email the office if you'd like to reserve it for your charter (no additional cost).

How can I access 12v power to charge a mobile device?

If your chosen boat does not have an inverter nor 12v USB ports, you can keep your mobile devices charged by bringing your own 12v USB device charger, such as the one pictured here.

Can I run the refrigerator away from shore power?

Please do not run refrigeration when the boat is disconnected from shore power. If you're wondering about refrigerators and the power they draw, see the article Charter Boat Icebox and Refrigerator Basics and Best Practices

Do you have a question about using electricity onboard? Please email our friendly office team and we'll add your question to this article.

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