Electric string trimmers come with motors that draw 3 to 6 amps of current, or about 1/8 to ¾ horsepower, and they range from 3 to 9.5 pounds in weight. A few electric models are heavier because they use a 6- or 12-volt direct current battery.
Gasoline powered trimmers use 2- or 4-cycle motors ranging in power from 1 to 2-1/2 horsepower. They are generally heavier and more expensive than electric trimmers. They offer greater power as well as freedom from a restricting electrical cord. Although there is no risk of electric shock, the gasoline/oil fuel mixture presents its own fire and burn injury hazards.
Electric string trimmers are quieter and easier to start than gasoline powered trimmers. They do not use volatile gasoline fuel, and they also require much less engine maintenance. However, you can’t use an electric trimmer beyond the radius of your heavy-duty 3-wire extension cord, which must be dragged about wherever you want to do your work. Such cords should be less than 150 feet long, because a longer wire sets up too much resistance to the electric current, causing a drop in voltage that can overheat the trimmer motor. Some electric trimmers are cordless, powered by rechargeable batteries. This gives you mobility, but you will only get about 45 minutes of useful work done before the unit needs to be recharged. Finally, cordless trimmers are also less powerful than other trimmer types.