How Long Will a Battery Power an Inverter?

Wondering how long a battery will run an inverter?

There’s a lot of complicated information on the subject so I wanted to write this article to make it easy for you.

We won’t get bogged down in charts and long formulas.

I will give you one EASY way to find out how long a battery will run an inverter!

In this article, you’ll get simple information for you to understand how long a battery will power an inverter.

So let’s dig in.

Calculating How Long a Battery Will Run an Inverter

The length of time your battery will last on an inverter depends on how much energy you are using. It is not your inverter that uses power but the appliances/device you plug it in too.

The only information you need to calculate this is the battery capacity in amp-hours (Ah) and the appliance load in watts.

You can find the battery capacity written on the battery usually something like 50Ah or 100Ah. For this example, we will use a 100Ah battery.

You can find the wattage of an appliance in small print on the device, in the user manual, or with a wattmeter.

Now you just need to use this formula:

(10 x battery capacity in amp hours) divided by (appliance load in watts)

So let’s say we want to use a 70 watt TV on a 100Ah battery. Using the formula above we calculate (10 x 100Ah) ÷ 70W = 14 hours.

That’s the quickest way to do a calculation of battery run time with any appliance or device wattage.

Pro tip: The above calculation assumes that your inverter is not 100% efficient. It includes an inverter efficiency of around 85%. Usually, inverters are between 85% and 95% efficient.

100Ah Battery and Inverter Run Time Examples

Here are some examples to give you an idea of how long different devices and inverters will run on a 100Ah battery:

Appliance and Wattage	Run Time Hours
Phone Charger – 5W	170
Laptop – 50W	17
Lightbulb – 60W	14.1
TV – 70W	12
Fan – 65W	13
Games Console – 200W	4.25
Refrigerator – 300W	2.8
Microwave – 700W	1.2
Coffee Maker – 1500W	0.5

Importance of Battery Type

Next, it’s important to understand the difference in performance depending on your battery type.

Generally, you will either have a lead-acid battery or a lithium battery.

Both work well as deep-cycle leisure batteries but the performance is a little different. Lithium batteries are more modern technology that offers better charging ability but they are more expensive. Lead-acid batteries have been around for decades, they have great durability but less charging capabilities.

What does this mean for you and why is it important?

Lead-Acid Batteries

While they are very durable and affordable they don’t cope well with being completely discharged. It can actually damage a lead-acid battery to use all of its energy until it is exhausted. It is best practice to keep it at least 50% charged to maintain its performance! This means you should treat it with half the capacity – e.g. think of a 100Ah as a 50Ah battery.

Lithium Batteries

These are the most modern battery types and what you will find in phones and laptops. You can also get big deep cycle lithium batteries too. They offer high-speed charging capabilities and can be charged from completely empty. This means you can use the energy supply in the battery to its maximum! Although it is best to leave a little juice in it to maintain performance so only discharge it to 95% to be safe.

Inverter Efficiency

I want to touch on the efficiency of your inverter as well. This is because inverters will use energy to run their own systems and convert DC to AC power.

Generally, you’ll an inverter will be between 90% and 95% efficient so won’t have too much impact.

In the calculations above, we included an 85% inverter efficiency rating to get a final battery run time. Using 85% keeps you covered for most inverters and gives you a bit of wiggle room in your battery supply. It’s better to underestimate efficiency than overestimate.

Match the Voltage

One other quick thing to consider when using an inverter with a battery is the voltage.

Inverters are built to work with a particular input voltage such as 12V, 24V, or 48V.

Batteries also have an output voltage of 12V, 24V, and 48V.

Your inverter voltage should match the battery voltage – most commonly this is 12V.

If you try to use a 12V inverter on a 24V inverter it will quickly overload and overheat. And vice-versa leads to undervoltage which leads to faults and potential damage.