Compare engines. Manufacturers rate engines in horsepower (hp). Higher horsepower engines power larger blades that can cut thicker branches. 1/2-hp models work well for 13-inch to 18-inch blades. Moderately powerful 1-hp trimmers work well for 20- to 26-inch blades. Commercial-grade trimmers with 40-inch blades range from 1 1/3 hp to 1 1/2 hp.
Compare blades. Blade length maximizes cutting efficiency. Small 13-inch blades take longer to cut hedges than a larger 24- or 40-inch blade. Single-sided blades operate safely because you can hold the cutting side away from you, but dual-sided blades can trim quicker. Carbon-steel blades last longer than metal alloys.
Consider the distance between the teeth. Larger gaps allow the blade to cut thicker branches. Smaller models often have tooth gaps of 1/2- to 3/4-inch. Larger, more powerful models have gaps of 1 to 1 1/4 inches.
Compare the weight of hedge trimmers. Hedge trimmers weigh 6 to 10 pounds. Look for even weight distribution in addition to light weight trimmers. Even weight distribution will help your stance and reduce pressure on your lower back.
Compare features. Many trimmers have features that help you cut more comfortably and effectively. Lock-on triggers keep the trigger depressed. Pole extensions allow you to trim hard-to-reach areas. Wrap-around handles allow you to comfortably hold the handle while reducing stress on your wrists and back.
Make sure the trimmer fits your budget. Low-power trimmers cost $80 to $200. Mid-level trimmers cost $300 to $500. High-power trimmers cost $500 to $800.