Gas

• Gas-powered trimmers are among the most powerful available, and that power allows you to work faster and cut more types of vegetation, including larger branches, heavy growth and thick vegetation. These trimmers are fueled by either a 2-cycle engine, which requires a gas/oil mixture, or a 4-cycle engine, which is the quieter and easier to start of the two and runs solely on gas. Gas-powered machines offer a wider cutting path than electric or battery-powered trimmers, and they are capable of reaching to cut large areas.
  
  

Electric

• Electric trimmers are among the least expensive trimmers. Their light weight makes them easier to use as they place less stress on your body. They produce less noise than a gas trimmer and are easier to start. Electric trimmers, however, require an extension cord connected to a power supply, so their reach is limited. Use of such a trimmer when the ground or targeted vegetation is wet may be hazardous.
  
  

Battery

• With battery-powered cordless trimmers, there is no hassle of working around a cord and no danger of cutting through the cord as you work. Battery-powered trimmers are lightweight and produce no exhaust. With multiple batteries, you may work without the interruption of waiting for a recharge. Those powered by lithium batteries tend to have a longer operating period than those that use nickel-cadmium batteries. This type of trimmer produces less noise than gas trimmers.
  
  

Propane

• A fourth trimmer option, the propane trimmer, runs from non-toxic, clean-burning propane, offering you a potentially more eco-friendly machine. One downside: you must purchase refill propane canisters, which can be difficult to find for sale. As of 2011, issues exist with the propane containers, which cannot be refilled, but they are recyclable. Propane produces minimal emissions, making it a greener option than electricity. Propane trimmers are as powerful as gas trimmers and easier to start, according to the Consumer Search website's ranking, but the website warns that propane trimmers tend to be heavier.