Wire-free vs boundary wire robot mowers

The two approaches in brief

A boundary wire robot follows a low voltage signal sent round a loop of wire from the charging station. When the mower detects the wire it turns back. Islands such as beds and trees are cut out with extra loops of the same wire, and a guide wire often helps the mower find its way home.

A wire-free robot knows its position by other means. RTK models use satellite positioning corrected by a reference antenna, or corrections from the cloud, to within a few centimetres. Vision and lidar models use cameras or laser scanning to see the lawn edge and landmarks. Many current models combine two or more of these. Our explainer on how robot mowers navigate goes into each method.

Four models side by side

The table uses listing facts for two wired and two wire-free robots from our guides. Figures not given in a listing are marked as not stated.

See the best wire-free robot mowers →

Installation and signal needs

Installing a boundary wire means walking the whole perimeter, pegging or burying the wire at the right distance from edges, looping round islands and joining it at the station. On a typical back garden that is half a day to a day of work, more on a large plot. Our guide to installing a robot mower boundary wire covers it step by step.

A wire-free RTK robot replaces that with mapping in an app, usually by driving the mower round the edge once. Many models need an RTK antenna placed with a wide view of the sky, though some, such as the Landroid Vision Cloud, take corrections from the cloud with no local antenna according to the listing. Vision and lidar models need no antenna but rely on clear sight lines and, for cameras, enough light. Our guide to setting up a wire-free robot mower covers placement and weak spots.

• Open lawn with clear sky: wire-free RTK is quick to set up and accurate.
• Lawn under large trees or between tall walls: a wire, or a model that adds vision or lidar to RTK.
• Several separate lawns: wire-free mapping avoids long extra runs of wire.
• Frequent layout changes: wire-free zones can be redrawn in minutes.

Accuracy near borders

A wired robot turns where the wire is, so the edge it leaves depends on where you laid the wire. Manuals set a distance from walls and raised edges, so there is usually an uncut strip to trim. Beside a flush path the wire can run closer and the mower can overhang the edge.

A wire-free robot follows the boundary you draw in the app. With a good RTK fix it can hold an edge to within a few centimetres, and several models, such as the Ecovacs Goat O1000 RTK with its TruEdge feature, list edge mowing as a selling point. When the signal is weak, accuracy drops, and most models then slow down, rely on cameras or stop rather than risk leaving the lawn.

When things go wrong

The classic boundary wire failure is a break. A spade, edging shears or a burrowing animal cuts the wire, the loop signal stops and the mower refuses to run. Finding the break can take time, though a cheap wire break detector helps, and many manuals explain how to locate and repair a break with waterproof connectors. See our guide to the no loop signal problem for typical causes.

The wire-free failure is a lost position. If tree cover, a new shed or scaffolding blocks the sky, an RTK robot may stop in that area or report weak signal. Moving the antenna higher, adding a camera assisted model or marking the area as a no-go zone are the usual fixes. Vision models can struggle in low light or where the lawn edge is hard to see, such as grass running into a gravel border.

Note:Before repairing a boundary wire or moving an antenna, switch the robot off and unplug the charging station power supply. Keep outdoor mains connections on an RCD protected socket, and use a registered electrician for any new outdoor wiring.

Which should you choose?

Go wire-free if your lawn is fairly open, you want to avoid installation work, or you change your garden layout often. It is also a strong choice for gardens with several lawns. Our best wire-free robot mower guide lists current options.

Stay with a boundary wire if your lawn is heavily shaded, enclosed by tall buildings or very complex, or if you want a lower cost entry point. Wired models in our robot mowers under £800 guide show how affordable they can be.

Frequently asked questions

Can a robot lawn mower work without a perimeter wire? Yes. Wire-free models use RTK satellite positioning, cameras or lidar, often combined, to stay inside a boundary you set in the app.

Are wire-free robots accurate enough near flower beds? With a good RTK fix they can hold an edge to within a few centimetres. Add a no-go zone with a small margin round delicate beds, and check performance in shaded corners.

What happens if the boundary wire breaks? The mower stops because it loses the loop signal. You need to find the break and join it with waterproof connectors, as described in your manual.

Do wire-free robots work under trees? It depends on the canopy and the model. Dense cover can weaken RTK, so models that add cameras or lidar cope better in shaded gardens.