# Countdown to Earth Day: kW = electric motor output; kWh = battery pack capacity

Chevrolet Volt battery pack

Understanding electric and plug-in vehicles requires a basic knowledge of the mechanics that make them move. Obviously, these two types of advanced vehicles have components (i.e. electric motors and massive battery packs) that more conventional gasoline- and diesel-fueled automobiles typically lack. Therefore, it's important everyone understand the basic units of measure that we use every day to describe the capacity values of these components.

Typically, the capacity value of an electric motor is written using kW (kilowatt). This unit of measure can be easily converted to horsepower. Here at AutoblogGreen, we often do the conversion for you. We hope that this makes it easier to compare an electric motor's output to that of a gasoline or diesel engine.

Meanwhile, the capacity value of a battery pack is often written using kWh. If you think kWh is similar to gallons – as in the total amount of gallons of fuel in a vehicle's tank – then you're on the right track. While kWh doesn't convert to gallons, it is used to signify the capacity of a battery pack, much like automakers list fuel tank size in gallons.

Yes, this is an oversimplified explanation of kW and kWh, but it is the way that AutoblogGreen uses kW and kWh. So, if we mention kW, it's often safe to assume that we're talking about the power output of an electric motor. Similarly, if we use kWh, it's almost guaranteed that we're discussing the capacity of a vehicle's battery pack.

This simplistic explanation of kW and kWh purposely omits the true complexities of both capacity values. If you're looking for an in-depth discussion of kW and kWh, check out this Greenlings article in our archives.

Note: To mark the 41st anniversary of Earth Day* this year on April 22nd, we're running a series called Countdown to Earth Day that we want to be very welcoming to new readers, both in topic and tone. We'll be returning to our Greenlings series for inspiration here, and if you have friends who you'd like to introduce to AutoblogGreen, perhaps these introductory posts and the coming "holiday" will be the spark to get their green car fire burning. Share them with your friends.

*Ironically, the apparent traditional gift for a 41st anniversary is land. Since land – earth – is something we can't easily create, perhaps this Earth Day we can give ourselves the gift of stewardship of the land.