300 and 600 Watt Inverters Compared: Small Inverters from 120 to 600 Watts
A small inverter runs a laptop, a TV, phone and tool chargers or a CPAP machine from a 12-volt battery. The decisions at this size are how it connects — a lighter socket, battery clamps or wired in — and whether your devices need pure sine wave. Here is how the small inverters we carry compare, from 120 to 600 watts.
- A vehicle power socket supplies only about 150 to 200 watts, so a 300-watt or larger inverter needs battery clamps or a wired connection to deliver its full rating
- Pure sine wave for laptops, CPAP machines and chargers; modified sine wave for lights, fans and simple tools
- A 300-watt inverter draws about 28 amps from a 12-volt battery at full load, a 600-watt one about 56 amps
- Check the continuous rating: the Xantrex PROwatt SW 600 is rated 540 watts continuous and 600 watts maximum
Pick by what you are running
| Continuous power | Waveform | Battery | Connects by | Extras | ||
|---|---|---|---|---|---|---|
|
Samlex PST‑120‑12
Laptop or CPAP
|
120 W | Pure sine | 12 V | Lighter plug | USB, hospital-approved | BUY NOW |
|
Samlex PST‑300‑12
Best 300 W pure sine
|
300 W | Pure sine | 12 V | Plug or clamps | 2 GFCI, 3-yr warranty | BUY NOW |
|
Samlex SSW‑350‑12A
Compact pure sine
|
350 W | Pure sine | 12 V | Not listed | 2 outlets | BUY NOW |
|
Samlex SAM‑450‑12
Budget pick
|
450 W | Modified sine | 12 V | Plug or clamps | USB 2.1 A, 2 outlets | BUY NOW |
Xantrex PROwatt SW 600
Display and USB
|
540 W | Pure sine | 12 V | Wired | 2 GFCI, USB, display | BUY NOW |
|
Samlex PST‑600‑12
Best 600 W pure sine
|
600 W | Pure sine | 12 V | Wired | 2 GFCI, remote option | BUY NOW |
Samlex PST‑300‑24
300 W for 24 V
|
300 W | Pure sine | 24 V | Plug or clamps | 2 GFCI, 3-yr warranty | BUY NOW |
Samlex PST‑600‑24
600 W for 24 V
|
600 W | Pure sine | 24 V | Wired | 2 GFCI, remote option | BUY NOW |
Can I plug a 300-watt inverter into a cigarette lighter socket?
Only for light loads. A vehicle power socket is fused at 15 to 20 amps, which is about 150 to 200 watts in practice. The PST-300 and SAM-450 come with both a plug-in cable and battery clamps: use the plug for a laptop or phone chargers, and the clamps for anything bigger. A 600-watt inverter should be wired to the battery.
How many amps does a 300-watt inverter draw?
About 28 amps from a 12-volt battery at full load — 300 watts divided by 12 volts, plus about 10% for losses. A 600-watt inverter draws about 56 amps, and a 120-watt one about 11. On a 24-volt system the current halves. Our inverter calculator works it out for your loads and gives the cable size.
What will a 300-watt inverter run?
A laptop, a TV, phone, camera and tool battery chargers, a fan, or a CPAP machine — usually without its heated humidifier, which can draw much more. It will not run a microwave, coffee maker, hair dryer or space heater; those need 1,000 watts or more.
Should I buy 300 or 600 watts?
Add up everything you will run at the same time and allow for the startup surge of anything with a motor — the inverter calculator does both. If you land near 300 watts, a 600-watt unit gives headroom, but it needs a wired battery connection rather than a plug.
Pure sine wave or modified sine wave for a small inverter?
Pure sine wave for laptops, CPAP machines, battery chargers and anything with electronics; they can run hotter, hum or fail to charge on modified sine wave. Modified sine wave, like the SAM-450-12, costs less and is fine for lights, fans and simple tools.
Bottom line
Start with what you will run and how you will connect. For a laptop or CPAP from a lighter socket, the Samlex PST-120-12 is the pick. The PST-300-12 is the best all-round small pure sine inverter, with a plug cable for light loads and clamps for its full rating; the SSW-350-12A is a compact alternative. For simple loads, the modified sine SAM-450-12 saves money, and for 600 watts, the PST-600-12 is wired to the battery. The 24-volt PST-300-24 and PST-600-24 cover 24-volt systems. Our inverter calculator checks the size.
