How a Boundary-Wire Robotic Mower Works
A robotic mower that uses a perimeter wire navigates by sensing a low-voltage signal sent through a loop of wire you install around the edges of your lawn. The mower stays inside that invisible fence, turns when it reaches the boundary, and follows a guide wire back to its charging station when the battery runs low or the schedule ends. The Greenworks Optimow operator manual explains that the boundary wire defines the cutting area, while an optional guide wire helps the mower find the charging station and reach remote parts of the yard more quickly.
Planning the Installation
Before you unbox the mower, walk the yard and check that conditions match what the manual requires. The Greenworks Optimow manual says the grass should be shorter than 4 inches before you begin, and the operating area must be even, with no ditches, grooves, or steep slopes greater than 35%. You will need a hammer or rubber mallet to drive pegs, combination pliers to cut the boundary wire, and a 6 mm hex key to secure the charging station. If your lawn has uneven terrain or tight passages, you may want to review our guide to choosing a mower by yard size and terrain before committing to a robotic model.
Placing and Connecting the Charging Station
The charging station needs a level spot out of direct sunlight. According to the Greenworks Optimow manual, the front end of the station must not be more than 2 inches higher or lower than the back end. Leave at least 10 feet of clear space in front and 3 feet to each side; do not tuck the station into a confined corner. The entire station must sit inside the boundary wire loop.
Connect the power supply in a cool, dry location, away from direct sun. If the outlet is outdoors, it must be approved for outdoor use. The low-voltage cable can cross the operating area if you staple it down or bury it, but the manual warns never to cut, splice, or alter that cable, because doing so voids the warranty. Thread the cable behind the tabs inside the station to hold it in place, then plug the power cord into a 100 to 120 V wall socket.
Laying the Boundary Wire
The boundary wire creates the invisible fence that keeps the mower on the grass. The Greenworks Optimow manual provides a table of distances for different obstacles, and those figures apply to that model. For fixed obstacles that are roughly level with the lawn, such as paving stone paths, lay the wire under the stones or in the joint between them. Never run the mower over gravel, mulch, or similar material that can damage the blades.
For low obstacles up to 0.4 inch high, place the wire 4 inches away. For obstacles between 0.4 and 2 inches high, such as small flower beds or low kerbstones, move the wire out to 12 inches. For fixed obstacles 2 inches or higher, like fences or walls, keep the wire 14 inches away. Tall obstacles over 6 inches that can withstand a collision, such as sturdy trees or shrubs, need no wire; the mower will turn when it bumps into them. Obstacles that cannot take a hit should be encircled with the wire 12 inches away, and the wire must return along the same route.
Long, narrow passages narrower than 5 feet call for a guide wire. Where the lawn borders a slope, road, precipice, or water, the manual says to supplement the boundary wire with a physical barrier at least 6 inches high. Slopes inside the cutting area are acceptable up to 35% for the Optimow, but if the outer edge of the lawn slopes more than 15%, do not lay the boundary wire on that slope unless a fence or wall is present to stop the mower. When a portion of the edge exceeds 15%, lay the boundary wire 7.8 inches in on the flat ground before the slope begins.
Secure the wire with pegs or bury it 0.4 to 8 inches deep. Pegs are recommended during the first few weeks because they let you adjust the layout. If you peg, cut the grass very low with a standard mower or a string trimmer along the wire path first. Push or hammer the pegs in without straining the wire. Connect the ends of the loop to the charging station terminals marked with left and right arrows, making sure the right-side wire goes to the right arrow.
Adding a Guide Wire
A guide wire is optional but recommended for narrow passages less than 10 feet wide or to shorten the time the mower spends searching for the charging station. The Greenworks Optimow manual instructs you to plan the guide wire route before you finish the boundary wire. Use the same cable roll for both wires. On a steep slope, lay the guide wire at an angle to the slope so the mower can follow it more easily. Avoid sharp angles and keep the guide wire at least 12 inches away from the boundary wire; never let it cross the boundary wire.
Run the guide wire straight under the charging plate in the track provided, then at least 6.5 feet straight out from the front edge of the plate. Leave as much open space as possible to the left of the guide wire when you face the station. At the far end, cut the boundary wire, insert both cut ends and the guide wire end into a splice connector, and squeeze the button with pliers until it clicks. Connect the guide wire to the terminal labeled G1 on the charging station. Some models support a second guide wire connected to G2.
Setup Checks and Initial Start
Before the first mow, secure the charging station base plate to the ground using only the five existing screw holes; do not drill new ones. The Greenworks Optimow manual notes that the LED on the station should glow solid green when the power supply is working and the boundary wire is intact. If the light is off or flashing, you need to troubleshoot the connections.
Pair the mower with the mobile app using the unique code from the quick guide. Set the cutting height to at least 2.4 inches for the first few weeks to avoid cutting the boundary or guide wire, then lower the setting one step each week until you reach the desired height. The table below summarizes key items to inspect before you let the mower run on its own.
| Setup Item | What to Check (Greenworks Optimow Manual) |
|---|---|
| Charging station position | Level, out of direct sun, 10 ft clear in front, 3 ft to each side, front-to-back height difference under 2 inches. |
| Boundary wire obstacle clearance | 4 in. from obstacles ≤0.4 in. high; 12 in. from 0.4 to 2 in. obstacles; 14 in. from obstacles ≥2 in.; no wire needed for sturdy obstacles over 6 in. |
| Slope at lawn edge | If edge slope exceeds 15%, wire must be 7.8 in. inside flat ground or a physical barrier must be present. |
| Guide wire path | At least 12 in. from boundary wire, no sharp angles, angled across steep slopes, at least 6.5 ft straight out from station. |
| LED indicator | Solid green means boundary wire and power supply are OK; off or flashing red signals a fault. |
Operating Safely Around People and Pets
The Greenworks Optimow manual stresses that the mower is a power tool with sharp blades. Never leave it to operate unattended if you know there are pets, children, or other people nearby. The manufacturer recommends programming the mower to run during hours when the area is free of people and pets. Always press the STOP button and remove the safety key before lifting the mower, clearing a blockage, or doing any maintenance. Keep hands and feet away from the blade disc, and wear protective gloves when handling the blades.
Routine Care and Blade Replacement
Regular cleaning keeps the mower cutting efficiently. After pressing STOP and removing the safety key, clean the exterior with a soft brush, a damp cloth, or a low-pressure water hose. Remove the body from the chassis, turn the mower on its side, and use a stiff brush or scraper to clear compacted grass from the blade area and wheels. For more seasonal upkeep, see our lawn mower maintenance checklist.
The manual states that the normal operating life of the blades is 2 to 6 weeks when the mower is used at maximum area capacity, and longer for smaller lawns. Dull blades tear the grass, drain the battery faster, and shorten the time between charges. Always replace all three blades and screws as a set, using only the original blade type specified for the model. Turn the mower upside down, loosen the screws with a straight-slot or cross-tip screwdriver, swap in the new blades with new screws, and check that each blade pivots freely.
Battery and Winter Storage
The battery is maintenance-free but has a limited service life. Before storing the mower for winter, charge the battery fully. The Greenworks Optimow manual cautions that a battery put away in a partially charged state can be damaged and in some cases become unusable. Inspect the blades and front wheels, correct any issues, and store the mower upright on all four wheels in a dry, frost-free place.
If possible, disconnect the boundary and guide wires from the charging station and bring the station and power supply indoors. Leave the wires in the ground but protect the ends from moisture by connecting them to an original coupler or placing them in a container of grease. If the station must stay outside, keep it connected to mains power and the wires. After winter, check the charging and contact strips for corrosion or dirt; the manual says to clean them with fine-grade emery cloth if needed. For broader guidance on off-season care, read our yard tool maintenance guide.
Frequently asked questions
How do I stop the mower from cutting the boundary wire?
Set the cutting height to at least 2.4 inches for the first few weeks after installation, as the Greenworks Optimow manual advises. Lower the setting one step each week until you reach your preferred height. This gives the wire time to settle and lets the grass grow over it, reducing the chance of blade contact.
Can the mower handle slopes?
According to the Greenworks Optimow manual, the mower can operate on slopes up to 35% inside the cutting area. However, the boundary wire should not be laid on an outer edge that slopes more than 15% unless a fence or wall is present. When the edge exceeds 15%, place the wire 7.8 inches inside the flat ground before the slope starts.
How often should I replace the blades?
The manual indicates that blades typically last 2 to 6 weeks when the mower runs at its maximum area capacity, and they last longer on smaller lawns. Replace all three blades and screws as a set whenever the grass looks torn or the mower’s runtime between charges drops noticeably.
For more help selecting and caring for lawn equipment, visit our Lawn Mowers category page.
