Marine Inverters & Inverter Chargers

A marine inverter turns the DC power stored in your batteries into the AC power used by household appliances: coffee makers, microwaves, televisions, chargers for laptops and phones. With the right inverter, you can enjoy those comforts at anchor without running the generator.

This guide explains the types of inverters used on boats, how to size one for your loads and your battery bank, what an inverter charger adds, and why installation is where most of the safety lies.

How a Marine Inverter Works

The inverter draws current from the battery bank and converts it from low-voltage DC (12, 24 or 48 volts) into 120-volt AC. It powers the outlets and appliances connected to it until the batteries reach their low-voltage limit.

That conversion has a cost: AC power at the outlet comes from a much larger DC current at the battery. A 1,000-watt load on a 12-volt system draws roughly 90 to 100 amps from the bank once efficiency losses are included. That is why the inverter, the battery bank and the cabling must be planned together, and why larger systems often move to 24 or 48 volts.

Pure Sine vs. Modified Sine Wave

Pure sine wave inverters produce clean AC power equivalent to, or better than, the power from the marina. They run every appliance correctly, including electronics, variable-speed motors, induction cooktops and battery chargers.

Modified sine wave inverters are cheaper but produce a stepped waveform. Some devices run hotter, buzz or fail to work at all. On a modern boat with sensitive electronics, we recommend pure sine wave in almost every case.

Sizing an Inverter

Add up the loads you want to run at the same time, in watts, and look at two figures on the specification sheet:

Continuous rating: the power the inverter can deliver for hours. It must cover your simultaneous loads with some margin.
Surge rating: the short peak it can deliver when motors, compressors or pumps start.

Then check the battery side. Running a microwave or an espresso machine from an inverter is easy for a few minutes; running air conditioning all night is a different project that needs a large lithium bank and a strong charging system. Our marine batteries guide explains how to size the bank.

Inverter Chargers

An inverter charger combines three devices in one: an inverter, a multi-stage battery charger and an automatic transfer switch. When shore power or the generator is available, it passes AC through to the boat and charges the batteries. When the AC source disappears, it switches to inverter mode within milliseconds.

Many models also offer power assist, which supplements a limited shore-power connection with battery power during peaks, and integrate with battery monitors and displays. Victron and Mastervolt are among the systems we install most often on yachts.

Installation and Safety

Inverters move large currents, so a professional installation is not optional. It includes:

DC cables sized for the full current and as short as possible, with a suitable fuse close to the battery.
Correct AC integration with the boat panel, including the transfer between shore, generator and inverter, so two sources can never feed the same circuit.
Proper neutral and ground handling, and ground-fault protection on the circuits that need it.
A dry, ventilated mounting location with space for the inverter to shed heat.
Configuration of charging profiles to match the battery chemistry.

Inverter Installation Across South Florida

OnBoat Marine designs and installs inverters and inverter chargers on site across Broward, Miami-Dade and Palm Beach counties, together with the battery banks and charging systems that support them.

See our battery banks and charging systems service, read our marine battery charger guide, or contact us to plan your system.

Frequently Asked Questions

What size inverter do I need for my boat?

Add the wattage of everything you want to run at the same time and choose an inverter whose continuous rating covers it with margin, and whose surge rating covers motor and compressor starts.

Can an inverter run my boat air conditioning?

It is possible, but it requires a large battery bank, usually lithium, and a strong charging system. For most boats the generator or shore power remains the practical source for air conditioning.

Is a modified sine wave inverter good enough?

For simple resistive loads it can work, but many electronics, motors and chargers run poorly on it. Pure sine wave is the safer choice on a modern boat.

What is the difference between an inverter and an inverter charger?

An inverter only converts DC to AC. An inverter charger also charges the batteries from shore power or the generator and switches automatically between sources.