How powerful a lawn trimmer is can typically be determined by its voltage. Usually, a higher voltage indicates a more powerful trimmer. Another indicator of power is its source. Overall, gas lawn trimmers provide a higher power level, although electric trimmers offer powerful options in both corded and cordless variations. The amount of power needed for a lawn trimmer depends on the size and types of hedges in the yard. Within Milwaukee String Trimmers, voltage ranges from 18v volts to 18v volts. Check out the product with the highest review count, the M18 FUEL 18V Brushless Cordless String Trimmer/Blower Combo kit with 8 Ah Battery and two 5 Ah Batteries.