What Battery Size for a 300-Watt Power Inverter

A 300-watt inverter is capable of converting DC (direct current) power from a battery or other power source into AC (alternating current) power that can be used to run small electronic devices and appliances. It’s important to ensure that the inverter is connected to a battery that is capable of supplying enough power to meet the device’s needs.

In this article, we look at what you can run off a 300-watt inverter and what battery to use.

What Can a 300-Watt Inverter Run?

The specific devices and appliances that a 300-watt inverter can run will depend on their power requirements, the efficiency of the inverter, and the system. 

Here are some examples of devices that a 300-watt power inverter could potentially run:

Laptop computers: Most laptops have power adapters that consume less than 90 watts, so a 300-watt power inverter should be able to run them without issue.

Small TVs: Some small LED TVs with a consumption of around 30 Watts. 

Portable DVD players: Portable DVD players typically consume less than 20 watts of power, so they should work well with the inverter.

Mobile phones and tablets: These devices typically require less than 10 watts of power, so a 300-watt power inverter could run multiple devices simultaneously.

It is actually possible to run all these devices together as long as you don’t exceed the continuous output of the inverter. 

The actual continuous output of a 300-watt inverter will be somewhere around 200 – 220 watts. This is because of the efficiency losses from converting DC power to AC power and losses through the wiring. This will also ensure that the inverter remains cool and you don’t overwork your fan. If you have more power requirements you can consider a 500-watt Inverter instead.

Also, ensure that the power output of the inverter matches the power input of your device. This can vary from 110v, 120v to 240v. 

What Battery Size for a 300-Watt Inverter?

The type and size of battery needed for a 300-watt power inverter will depend on several factors, such as the desired runtime, the load (devices/appliances) being powered, and the inverter’s efficiency. Let’s first take a look at the amp drawn from the battery. 

How Many Amps Does a 300-Watt Inverter Draw?

To calculate the amps required you divide the Watts by the voltage. The voltage in a battery bank is usually between 12v for a small 300W system. This is what is referred to as the input voltage. Let’s take a look at how many amps the inverter will draw from a 12v battery at the max continuous rating (200W)


300/12 = 25 Amps 

You’ll need a battery bank that can support 25 amps in one hour for a 12v system. 

How Many Amp-hours to run on the 300-Watt Inverter?

Deep batteries are recommended to be discharged at 0.2C or at 20% capacity. So for 25 amps, you’ll need a 125Ah battery. This battery can last up to 5 hours with a 300-watt continuous draw.  But in order to reserve capacity, you should use a battery of at least 150Ah. However, remember we are only drawing 200 watts continually or 16 amps. 

A 12V 100Ah Lithium battery will last more than 6 hours with a 200-watt appliance or appliances with a combined 200-watt need. 

You can use a smaller battery if your device needs are less. 

For example, with a 30-Watt LED TV, the draw will be around 2.5 amps. With a 2.5 amp draw, you can power a TV for up to 20 hours with a 50Ah Lithium battery. You could potentially add other items like a DVD player or PS5 and the inverter and battery will be able to support these appliances. 


A 300-watt power inverter can run several devices but the main factor that determines what it can run and how long it can run an appliance for is the power source or the battery. A small 50Ah battery can run a small tv for a long period of time but if you were to add other appliances to this you will need a bigger battery.

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