Power inverters convert direct current power like that from an RV battery bank or solar power system into alternating current or AC power. What should you consider when purchasing a power inverter? What factors matter when you’re shopping for a power inverter? And what factors shouldn’t really affect the decision?

1. Wattage

How much power can the inverter supply? Low wattage devices tend to be cheaper and smaller but it will at best trickle charge your batteries if you’re using the device plugged into it. On the other hand, it can plug into the car or RV’s dashboard. It may even charge the device while you’re driving, pulling from the car engine’s power instead of drawing from house batteries. Low wattage devices like this typically have a single USB port and electrical plug.

High wattage power inverters can provide enough power to run high demand appliances like vacuum cleaners and space heaters. These inverters tend to be much larger. They may add to the noise level in the RV, too, if they need fans to keep cool.

Choose the inverter based on the standard load you expect to put it under with an additional 15 to 25 percent margin. For example, the standard coffee maker uses 300 watts, an LCD TV 120 watts and a laptop 100 watts. This means the inverter must be able to supply 520 watts of continuous power while everything is plugged in.

However, you may want to turn on lights and use another small appliance. And the coffee maker and TV draw extra power when they’re first turned on. This means you shouldn’t buy an inverter unless it can deliver at least 600 watts of power. A refrigerator requires 1500 to 2000 Watts.

Heavy duty power chargers / inverters tend to deliver high power but at low quality. You’ll be able to run power tools like drills and heavy draw appliances like blenders, but don’t plug your smart phone into it to charge without an additional level protection like a surge protector.

The alternative is having a second smaller inverter that lets you safely charge sensitive electronics via the vehicle dashboard. That increases the cost of hardware, but you don’t have to try to make a single inverter/charger do everything. And if the main high-power inverter is burned out, the smaller one should still work.

2. Power Quality

Power quality refers to the stability in the voltage and harmonics. A system with lower power quality may put out a harsh square wave though it is alternating current. This will cause excessive jerking and vibration in a high-power motor like those found in an air conditioner or vacuum cleaner.

Low power quality is a greater problem in sensitive electronics. It can burn out circuits in control boards for CPAP machines and smart phones. If you’re going to be plugging smart electronics or medical devices into the power inverter, high power quality is a necessity.

Know that medical grade inverters can safely charge your smart devices like cell phones. Just don’t pay for medical grade inverters if it isn’t necessary, and look for power quality standards that make an inverter safe for medical devices though they aren’t specifically labeled as such.  You also want to try and focus on options outlined at the Clean Energy Project as well.

3. Power Outlets

Nearly every AC inverter has at least one conventional power plug equivalent to those in your home’s walls. However, inverters vary in how many power outlets they have. If you want to run two or more plugged-in AC appliances at once, your inverter needs that many plugs or you need to risk greater power loss by plugging in a power strip.

What if you want to charge or power devices with an USB charging port like a smart phone or tablet? You’ll lose power if you have to connect a converter to the inverter. On the other hand, inverters with USB power plugs eliminate the need for this hardware and will charge your devices faster.

4. Safety Features

You shouldn’t buy a power inverter without comparing the safety features it has. The ability to monitor voltage is useful. Knowing that it has over-voltage protection, surge protection and over-heating protection is worth paying more for, since this both protects you and downstream electronics.

You should consider picking up power inverters that protect upstream power sources, too, such as not letting low house batteries pull power from your charged devices.

Just make sure the inverter doesn’t have a basic fuse that offers no protection at all when it has burned out. And verify that you can get replacement fuses and other safety devices when they are tripped on your power inverter.

5. Power Storage Capability

Power inverters are often a massive capacitor, though that’s more true of inverter/chargers. This allows it to store up power and then deliver it at a steady pace to downstream devices. Where power inverters differ is how they can use the extra power they’ve stored up.

Some power inverters can deliver “surge” power or “peak” power. For example, your air conditioner may need 700 watts to run but kicking in the compressor requires an additional 200 watts. That means you actually need 900 watts of power to start up the air conditioner.

Some power inverters can provide that “peak” power for a few moments. That can prevent the inverter and batteries from being overloaded when there is a moment of peak demand from electrical devices. That results in fewer blown fuses.

6. Size/Weight

When you live in an RV, weight and space are both at a premium. You have few places to put an electrical device. That’s a point in favor of small inverters and inverter/chargers, and it leads some to choose inverters they can plug into a vehicle dashboard.

(Don’t get an under-powered inverter, though.) Smaller and lighter units mean you have fewer issues finding a place to put them, and they are less likely to become a trip hazard.

Ideally, the inverter/charger will fit in the utility panel of the RV or sit next to the battery bank, though that’s not always an option.

Conclusion

The best inverter will power the devices you want to run as a base load. It will safely power and charge sensitive electronics without forcing you to constantly plug and unplug devices. It won’t take up a lot of space or weigh down the vehicle, while it protects the devices and batteries from power fluctuations.