Line trimmers

Power matters when it comes to choosing a line trimmer – the more grunt it has, the easier it’ll knock over the grass and weeds in your garden. Petrol engines pack the most punch and are the best choice for a hard day’s trimming. However, battery models aren’t far behind and are more than capable of handling the average suburban section.

Petrol-powered line trimmers

Petrol engines reign supreme when it comes to performance and endurance, especially for levelling long grass and weeds. But they’re heavy, noisy and sometimes a pain to start.

Most line trimmers are powered by two-stroke motors, so there’s the hassle of mixing oil and petrol, as well as dealing with the noxious fumes and emissions.

They’re also less reliable than electric models – in our 2016 appliance reliability survey, 17% of petrol trimmer owners had experienced a problem requiring repair, compared with 6% for cordless-electric models.

Cordless (battery-electric) line trimmers

Cordless line trimmers are closing the gap on petrol, driven by innovation at both ends of the trimmer. Brushless DC motors, once confined to high-end power tools for tradies, are increasingly making their way into domestic cordless gear. They deliver more torque with greater efficiency, and are lighter than brushed versions traditionally found in electric tools.

The other big factors are the falling price and improving capacity-to-weight ratio of lithium-ion batteries. Our best line trimmers give 30 to 45 minutes’ runtime out of the box.

Another big advantage of electric outdoor gear is it starts with the push of a button or pull of a trigger, compared with the hassle of fiddling with a choke and primer then yanking a start cord.

Mains-electric line trimmers

Mains-electric trimmers have been eclipsed by cordless models when it comes to performance, but they can be a good, affordable option for tidying up patches of grass or weeds closer to home.

Manufacturers of cordless power gear usually market their products as members of a universal battery platform. The idea is you’ll buy your first tool as a kit including a battery and charger, then for subsequent tools you just need to buy the “skin” (the tool only).

We tested the line and hedge trimmers sold from Ryobi’s One+ range, and they returned reasonably good performance. They’re outclassed by higher-voltage tools (36V and above), though they’re a viable option for lighter jobs.

When shopping for cordless power equipment and batteries, you should consider volts (V) and amp-hours (Ah). For mains-electric models, all you need to worry about is watts (W).

• Volts (V) indicate the power of a battery. The best cordless line and hedge trimmers use 36, 40 or 56V batteries. A tool of a certain voltage can only be powered by a battery of the same voltage.
• Amp-hours (Ah) measure battery capacity, which gives you an idea of the runtime. A 1.0Ah battery is rated to deliver one amp for an hour before running out of juice. Typically, lithium-ion batteries for power gear range from 1 to 5Ah. A 2.0Ah battery gives about 30 minutes’ line trimming.
• Watts (W) show the power of an electric motor, and are usually only quoted for mains-electric (corded) products. Hedge trimmers generally range from 400 to 600W, but we find 500W is powerful enough to give a good cut on most domestic hedges.
  

• Line-feed system. Line trimmers use a string-like line to cut with. To get more line, most trimmers use a bump system, where you tap the head on the ground to get more line. Some electric trimmers use an automatic feed that gives more line when you pull the throttle. This generally doesn’t work as well as a bump feed. A few entry-level petrol and electric trimmers use a manual feed – you turn off the trimmer to replace the line or plastic blades.
  
• Balance is just as important as weight. Before you buy, hold the trimmer in the cutting position, with your dominant hand on the trigger and the other on the front handle: its weight should feel evenly distributed between the top and bottom of the shaft, or a little heavier on top.
• Straight or curved shaft? Curved shafts keep the cutting head at a good angle for trimming grass and are generally easier to wield, but straight shafts are the best choice for taller users and heavy-duty work, as they give a longer reach.
  
• Starting is another big gripe for owners of petrol trimmers – see the “ease of starting” scores in the line trimmer profiles. Electric trimmers all score perfectly in this category as they start at the pull of a trigger.
  
• Safety guards are mounted on the rear of the cutting head to protect you from debris. A good guard shouldn't limit your view.
• Line-limiting blades chop the line off at the right length if you unspool too much. The blades are mounted on the safety guard.
  
• A shoulder harness shifts the trimmer's weight from your arms to your shoulders. It’s usually an optional extra. Longhorn-style handles also help ease the load and make controlling the trimmer much easier, but they're typically found on more expensive commercial models.
  
• Front handles should be adjustable. Most can be rotated around the shaft when you flip the cutting head over to edge your lawn.