What Size Inverter Do I Need?

Looking at all the inverter options can be overwhelming. What are all the numbers, and what do they mean?

If you’re not an electrician, it can be tricky to figure out how to find an inverter that will meet your power needs without letting you down when you’re out camping.

This guide will help you pick the best inverter size for your needs. 

How to Choose an Inverter Size  #

When you’re choosing a power inverter, there are two measurements you need to know. First, you need to know the typical power usage of the appliances you want to run. For example, if you want to use a coffee maker and your laptop, you will need to know how much power each device uses during continuous use. 

Next, you need to know the surge power usage. Surge power is a measurement of how much power a device needs to start-up or do other high-power functions. For example, the surge power of your coffee maker might be much higher when the machine is actively brewing than when it’s keeping the pot warm. 

Even though your devices will only need surge power levels briefly, your inverter should comfortably handle that amount of power. If your inverter isn’t rated to handle that much power, you could easily damage it or your appliances if any of your devices surge.

How to Calculate a Power Estimate #

Before you pick your inverter size, you need an estimate of how much power you’ll be using. This calculation will tell you if your battery set-up is enough for your power needs as well as the right size for your inverter. 

What You’re Powering #

Start by making a list of all the devices you’ll want to power and their maximum power usage. Your devices should all have this information available in watts. If your caravan has many modern comforts like air conditioning, refrigeration, or heating, you will likely have higher power needs than if you’re trying to run a small appliance, like a 240V TV. 

Add up the wattage for all of the devices you plan to use at the same time. Make sure to include a little room for unexpected power surges. If you know any of your devices use significantly more power to start up or perform certain functions, take that into account as well.

How Long You’re Using It #

In addition to what you are using, you need to think about how you’ll be using it. Running all of your equipment simultaneously is a considerably higher power draw than if you are using appliances one at a time. 

The amount of time you want to use these devices between charges is important too. If you know you’ll have about eight hours between battery charges, you’ll want to calculate how much power you’ll need to run your devices in that eight hour period.

The calculation will be different for different appliances. For example, a refrigerator will need continuous power, whereas you’re less likely to run a coffee maker for the entire eight hour period. 

How to Calculate Your Power Usage #

Once you have the number of AC watts you need, you still need to figure out what that translates to in DC amps. The whole point of an inverter is to change the DC power from your batteries into AC power for your devices. Until you make that calculation, you won’t know what inverter size is right. 

To calculate the DC amps using your AC wattage need, you need to divide the AC watts by the DC voltage of your battery set up. 12 volt is the most common battery voltage.

So, for example, if you need 2000 AC watts you would calculate your DC amps like this:

2000 AC watts / 12 volts = 166.67 DC amps per hour

In this example, you would need an inverter with more than 2000 watts capacity and a battery set up that will give you at least 167 DC amps per hour.  

Can Your Battery Handle It? #

Once you know your inverter size, you need to make sure it is compatible with your battery set up. Batteries are rated in DC amps per hour, so you can use your conversion results to figure out the right battery capacity. 

Converting the power from AC to DC will use a little power, which you need to factor in. The inverter will use roughly five percent of the total power, so in this example, five percent of 166.67. 

That comes out to about 8 DC amps per hour. Add that to your conversion:

166.67 DC amps + 8 DC amps = 174.67 DC amps per hour

Rounding up, for this example, you would need a battery capacity of 175 DC amps per hour. 

Making the Most of Your Inverter & Batteries #

When you’re camping, space and weight are at a premium. Having an inverter/battery combo that lets you run every electronic device you own at once isn’t useful if you don’t also have the space to pack those electronics.

You also want to maximize effectiveness and minimize annoyances, like background hums or overheating.

Battery Considerations #

Lithium batteries are lighter weight than lead-acid AGM batteries. Lithium also has the advantage of using more of its capacity between charges. Lead-acid batteries can only use about half of their energy capacity between charges, whereas lithium batteries are closer to 95% usage.

What that means is that for the same amount of power, you’ll need two lead-acid batteries for every one lithium battery. Even if the batteries have the same power rating, lithium batteries are the better choice. 

Even if you have the fanciest inverter in the world, your battery supply has to be functional to reap the benefits of your inverter.

Baintech Lithium Batteries #

Lithium batteries provide more usable capacity than lead acid batteries. Deep discharging does not affect the life of a lithium battery the way it does with lead acid batteries. You can use the battery longer before needing to recharge, without damage to the battery.

Cost Effective Over Life Cycle #

When considering the usable capacity and lifespan of lithium batteries, they work out cheaper than lead acid. When you add the cost and inconvenience of refitting new lead-based batteries every few years the total cost of ownership over the long term is far better with lithium batteries.

High Power Range #

Baintech have a range of HP (High Power) Batteries, suited for use with inverters. The Baintech HP battery range can power larger loads up to 200A of continuous discharge and 500A surge. It can also be charged at up to 150A, replenishing the battery in less than 1 hour. These high-power units can be placed into parallel for capacity increase and current increases to power massive loads including air-conditions.

Parallel Capabilities  #

All our SP range of Lithium batteries have a 100 Amp continuous BMS so they will run up to a 1000 Watt Inverter.

By paralleling two SP batteries, you can run up to a 2000 watt inverter. 

Inverter Considerations #

For the best inverter, look for a pure sinewave device. These inverters have a lot of advantages over modified inverters, including lower operating temperatures and energy usage. Pure sinewave inverters can be more expensive than other varieties, but the quality is worth it.

When you use a pure sinewave inverter, you have broader device compatibility and a cleaner power source. You are less likely to have irritating background noises or power failures than with a less sophisticated inverter. 

Inverters are an investment. The last thing you want is for your inverter to fail when you’re camping off the grid, far from civilization!

Get Your Inverter and Get On the Road #

Whether you need a small inverter to charge your cell phone and GPS or a larger one to run a microwave and refrigerator, we have you covered. Reach out today for inverter buying tips and other resources.

We’ll have you fully charged and on the road in no time. 

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