What will a 400 watt Power Inverter Run?

A 400 watt power inverter is a small, light-weight, and portable inverter, that is handy for use while traveling whether camping or in an RV.

You can use it to power devices with 110V AC from a 12V battery supply provided they consume up no more than 400 watts of continuous power.

With the several appliances out there each with different power consumption, and given limited power supply capabilities of the 400 watt power inverter, it may not be easy to tell which appliances can be safely connected to the inverter.

So in this article, I will provide a list of devices that you can connect safely to the inverter, how to check which appliances are most likely to work with the inverter and which ones will not without risk of damage to it.

What Devices Can be Powered by a 400 watt Inverter?

A 400 watt inverter can run one or more appliances provided their combined continuous power consumption does not exceed 400 watts and the surge power1 is less than 800 watts.

Examples of appliances you can expect to run on your 400 watt inverter include:

Note: The list is not exhaustive

What will a 400 watt inverter run

  • Laptop(s)
  • TV
  • Phones and Tablets
  • LED and Incandescent lights
  • Low power tools
  • Mini fridge (check that its continuous and surge power draw are within limits of the inverter)

Examples of appliances that most likely cannot be powered by the 400 watt inverter due to their typically higher power draws include space heaters, electric kettles, flat iron, electric blanket, microwaves, larger fridges, and electric heaters.

Note: This is a guide, always check the continuous and surge power draw of the appliance before plugging it into the inverter.

1Surge power is the momentary power drawn by inductive appliances (have windings or motors) such as motors, some TVs, Fridges.

How to Determine the Power Rating of an Appliance that Can Run on the Inverter

The easiest way to find out the power rating of an appliance is to consult its owner manual.

The power consumption in watts is usually listed in the technical specifications section of the manual.

Another way is to check the nameplate of the appliance. Sometimes the power consumption (watts) is listed there.

If it is not and only the voltage (V) and current (A) are shown, you can work out an estimate of the appliance’s power draw from the formula, voltage (V) and current (A) = power consumption of the appliance in watts.

For example, a laptop’s nameplate shows a voltage of 110V and a current draw of 0.5 A at that voltage, then its power consumption is 110V x 0.5A = 55 watts which is within the limits of the 400 watt inverter.

How Long a 400 watt inverter Can Run Devices on a 12V Battery?

There is no one answer to this – it really depends on the total power consumption of the appliances connected to the inverter, the capacity of the battery, and its state of charge – whether it is fully charged or partially charged.

For example:

A 400 watt inverter (with connected appliances drawing 400 watts of power) will run for about 1.5 hours when connected to a fully charged 100Ah AGM or GEL battery with a recommended depth of discharge of 50%.

With a fully charged 200Ah AGM or GEL battery, the 400 watt inverter (fully loaded) will run for about 3 hours.

How Long a 400 watt Inverter Can Run Devices on a 12V Car Battery?

The runtime of a fully-loaded 400 watt inverter on a car battery is considerably less because car batteries are starting batteries are not meant to be deeply discharged for them to last.

As a guide, the 400 watt inverter (with connected appliances drawing 400 watts of power) will run for about 55 minutes when connected to a fully charged 100Ah AGM Starting battery with a recommended depth of discharge of 30%.

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When running the inverter on the battery, it is recommended that you keep the engine running to prevent the inverter from draining the battery to a point where the car is not able to start.

Inverter low battery alarm with car engine start

If the inverter is connected to the car battery in the car, starting the car engine may trigger the inverter’s low battery alarm and force the inverter to shut down.

In this case, switch of the inverter and then switch it on again once the engine is running.

How Many batteries you Need to Run a 400 watt Inverter?

The number of batteries to connect to your 400 watt inverter depends on the time (hours) you plan the appliances to run for.

You can consider connecting 1 x 50 Ah, 2 x 50 Ah, 1 x 100Ah deep cycle batteries with a recommended depth of discharge of 50%.

How Many Amps a 400 watt Inverter draws when Running?

A 400 watt inverter has a no-load current draw of up to 0.4 – 0.6 amps or less depending on the design of the inverter.

More efficient inverters can draw considerably less current from the battery. At full load, the 400 watt inverter can draw up to an estimated 33.3 amps from a 12V battery.

To avoid the car battery being drained flat over time, switch off the inverter if there are no connected appliances.

If the inverter has a mode to conserve power draw, make sure to activate it.

On some inverters, the current draw reduces to as low as 0.25 amps or less when this energy-saving mode is activated.

Final Word

The 400 watt inverter is suited to low-power electronic and electrical appliances whose maximum power draw does not exceed 400 watts and surge power no more than 800 watts.

Examples of appliances are laptops, TVs, some mini fridges, and lights provided its continuous and surge power requirements are not exceeded.

The inverter’s runtime on battery depends on the power draw of connected appliances, battery capacity, and the state of charge of the battery.

You can increase the battery runtime by increasing the battery capacity or switching off appliances that are not required at the time.

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