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boat power inverters comparison, in stock
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What an inverter does aboard
An inverter converts the DC power in your batteries to 120V AC, the same as a household outlet in the US. It lets you charge laptops, power tool batteries, drones and cameras and, with bigger units, run a coffee maker, a kettle or a small microwave. What it cannot do is make energy: everything it delivers comes out of your batteries, with an efficiency loss of 8 to 12 percent.
If you sleep at the dock, a battery charger on shore power is still the way to have permanent AC. The inverter is for the hook or underway.
Pure sine wave or modified
Pure sine wave matches what the grid supplies and is the only sensible choice for sensitive electronics: laptop chargers, switch-mode power supplies, compressors and motors. Modified sine wave is cheaper but can make some devices buzz, run hot or not work at all. On a boat, where chargers, navigation gear and refrigeration share the system, pure sine is worth the extra money.
How many watts you need
Add up the watts of whatever runs at the same time and add a 20 to 30 percent margin. Look at continuous output, not surge, and remember that VA is not the same as watts.
| 120V device | Typical draw | Minimum inverter | Current at 12V |
|---|---|---|---|
| Phone or tablet charger | 10-30 W | 150 W | 1-3 A |
| Laptop charger | 65-100 W | 250 W | 6-10 A |
| Power tool charger | 50-150 W | 300 W | 5-14 A |
| Small LED TV | 40-80 W | 250 W | 4-8 A |
| E-bike charger | 200-400 W | 500-800 W | 18-37 A |
| Small microwave | 1,000-1,300 W | 1,500-2,000 W | 95-125 A |
| Pod coffee maker | 1,200-1,450 W | 1,500-2,000 W | 110-135 A |
| Hair dryer | 1,500-2,000 W | 2,000 W or more | 140-185 A |
Look at the last column: a 2,000 W inverter at full load pulls over 180 A. A small lead-acid battery cannot deliver that; a bank of lithium batteries can, as long as its BMS allows that current.
Cable, fuse and installation
At 12V the currents are large, and that is where trouble starts. These are rough figures for short runs (up to about 6 ft between battery and inverter); always follow the manufacturer's table:
| Inverter | Typical cable size |
|---|---|
| 300 W | 10 AWG |
| 500 W | 8 AWG |
| 1,000 W | 4 AWG |
| 2,000 W | 2/0 AWG or larger |
- Connect it to the house bank, never to the starting battery.
- Fit a correctly rated fuse as close as possible to the battery positive terminal.
- Add a battery switch so you can shut it off when not in use: even idle, it draws current.
- Use properly crimped lugs and the shortest cable run you can.
- Mount it in a dry, ventilated spot, away from gasoline and propane: it gets warm under load.
Watch out: an undersized cable heats up, drops voltage and can start a fire. With a large inverter, do not skimp on cable or terminals.
Common mistakes
- Buying on the surge number instead of continuous output.
- Leaving the inverter on with nothing plugged in: it drains the battery for nothing.
- Running resistive loads (kettles, heaters) for long: they empty a bank in minutes.
- Not checking voltage drop across the cable under load with a multimeter.
Tip: if you only charge laptops and cameras, a 300 to 500 W pure sine unit is enough and idles on very little. Keep the 1,500 W and larger models for people who truly need them and have the battery capacity behind them.
The models above were chosen from spec sheets and verified customer reviews, not our own tests.
Frequently asked questions
What size inverter do I need on my boat?
Add up the watts of what you will run at once and add a 20 to 30 percent margin. For laptops, cameras and tool chargers, 300 to 500 W is enough. A coffee maker or small microwave needs 1,500 to 2,000 W plus a battery and cabling rated for over 100 A.
Pure sine wave or modified sine wave?
Pure sine wave. It runs laptop chargers, motors, compressors and sensitive electronics without trouble. Modified is cheaper, but some devices buzz, overheat or perform poorly on it.
How much battery does a 1,000 W inverter use?
At full load, about 90 to 95 amps from a 12V battery, assuming 88 to 92 percent efficiency. That is why it suits short loads or lithium banks.
Can I connect the inverter to the starting battery?
It is better not to. You could drain it and be unable to start the engine. Connect it to the house bank with its own fuse and battery switch.
