Selecting the Correct Power Inverter

A power inverter converts 12-volt DC power from your batteries to 120-volt AC to power your standard appliances. Planning to take a camping trip? If you do not have easy access to AC power, how long can you go and how much can you power? What power inverter is the best size for you and what should you consider when looking to purchase a power inverter?

First, make sure you have enough power. Inverters are rated in watts, and almost all electrical appliances have a corresponding rating. (chart below)

Next, choose the right batteries. One of the most crucial factors of the success of your installation is your choice of DC power source.

Conventional starting batteries are not the recommended for power inverters. Power inverters require batteries designed for deep discharge/recharge cycles during normal operation. Starting batteries are made to deliver a very fast “starting” burst of power to start an engine and are then recharged by the vehicle’s charging system. Deep Cycle batteries are made to be deeply discharged and recharged multiple times without causing any damage to the battery. Deep Cycle batteries are usually rated in Amp Hours. Amp Hours provide a rating of how long the battery can supply power over a certain timespan.

To determine the battery capacity and inverter power you will need, you’ll first add up all the wattage requirements for each appliance or device you’ll be powering. If the item is listed only in amps, just multiply the amp draw by 120. Then, determine the length of time each item will be powered by the inverter & battery it is connected to. Multiply [Required Watts] by [Hours Run] for each item, which gives you the watt-hours required for each. Add each device’s watt-hour requirements together for the final, total watt-hours you will need. Divide your total watt-hours by 120 to get your amp hour requirement.

When choosing your battery, a good rule is to use one with a total capacity (Ah) that is at least twice your amp hour requirement. This will give you some wiggle room if you need more run time than you are expecting. This will also prevent your battery(ies) from completely discharging which will increase battery life and longevity.

When you are using multiple batteries to power the inverter, you should ensure that all of the batteries used are the same manufacturer, type, capacity, state of charge, and age so the system will perform in a stable manner. In situations where multiple batteries are connected in series, parallel, or series/parallel, replacement batteries should be the same size, type, and age. Do not put a new battery in a group that is several months or years old. Replace the entire group or add a good used battery.

Lastly, purchase a good battery charger to fully charge your batteries back up after they have been used with your inverter.

Wattage of Common Appliances