Choosing a robot lawn mower shouldn't come down to whichever sponsored listing tops the search results. Every garden is a different mix of size, slope, obstacles and shape, and those four things decide whether a robot copes far more than the badge on its lid. This guide covers what actually separates a good buy from a mower that does half the job, written for British lawns: damp, often clay-heavy, frequently sloping and shared with hedgehogs.
How much lawn will it really cover?
Manufacturers quote "up to X m²" under ideal conditions: flat ground, no obstacles and the robot working long hours every day. The more flower beds, trees, tight corners and narrow passages your garden has, the further real-world performance drifts from that headline figure.
For reference, a typical semi-detached back garden in England has somewhere between 50 and 150 m² of lawn (roughly 550-1,600 sq ft); a large detached plot can easily run to 500-1,000 m². Measure yours properly before you shop. Pacing it out is fine for a rough idea, but the area tools in Google Maps or most mower apps are more accurate.
Buy a model rated for at least 20-30% more than your actual lawn, and more again if it is steep, cluttered or split into several areas. In May and June, when British grass grows fastest, a robot working at its limit simply can't keep up.
Boundary wire, RTK or vision: the choice that changes installation most
A boundary wire (also called a perimeter wire) is still the cheapest and most proven option. You peg it down or bury it a few centimetres deep around the edge of the lawn and around any island you want avoided, and the mower turns back when it detects the signal. For a simple, rectangular lawn it remains the sensible choice, and it doesn't care about trees, cloud or Wi-Fi.
Wire-free mowers use RTK satellite positioning, LiDAR or cameras (often a combination) to follow a virtual boundary you draw in an app. They make multiple zones, irregular shapes and redesigns far easier, but they cost more and each technology has a weak spot: RTK struggles under dense trees and next to tall houses, while camera-only models need decent daylight.
When paying extra to avoid the wire makes sense
If your lawn is split into separate areas (front and back joined by a side path, say), has lots of beds and specimen trees, or you change the layout often, wire-free saves you the cost and hassle of re-laying the perimeter every time. We go into detail in boundary wire vs wire-free and explain the navigation types in RTK vs LiDAR vs vision.
Slopes: the spec most often overstated
The maximum slope a manufacturer quotes is measured under controlled conditions, usually driving straight up. Turning on a slope needs more grip than that single figure suggests, and wet British grass, especially on clay soil, cuts traction further. If your garden has a bank, don't buy a robot that only just matches it on paper: leave a good margin.
Remember that slope figures come in percentages, not degrees: 100% is 45°, and 35% is only about 19°. Our guide to robot mowers for slopes explains how to measure yours with a spirit level and a straight batten.
Battery, charging and scheduling
More important than runtime in minutes is how many times the mower has to return to charge to finish your whole lawn, and how long each charge takes. A robot that mows for a shorter spell but recharges quickly and resumes where it left off usually performs better day to day than one with a bigger battery and slow charging.
App scheduling lets you set quiet hours (handy with neighbours on both sides) and adjust frequency through the season. In the UK the main mowing season runs roughly from March to October: growth surges in late spring, slows in a dry July or August, picks up again with autumn rain and then stops. Some models adjust their hours automatically based on growth or the weather.
Safety, theft and hedgehogs
A robot mower lives outside, unattended, with blades spinning. These features are basics, not extras:
- Lift and tilt sensors: stop the blades instantly if someone picks the mower up or it tips.
- Rain sensor: pauses mowing when the grass is wet, which clumps clippings and strains the motor. In a British climate this matters more than an IP rating alone.
- PIN code, alarm and GPS tracking: the real difference between getting a stolen mower back or not. Robot mowers are a known target in the UK; check whether tracking needs an extra module or a subscription.
Hedgehogs: they forage at night and freeze rather than run when threatened, so the single most important setting is a daylight-only schedule. Don't mow between dusk and dawn, check long grass and hedge bottoms before the first run of the day, and leave a wild corner outside the mowing zone. Obstacle-detecting cameras help, but a sensible schedule is the real protection.
Browse robot lawn mowers on Amazon →
Noise and neighbours
Robot mowers are far quieter than a petrol or corded mower, typically a low hum you notice only close up, which is why many owners run them most days. If your garden backs onto a neighbour's patio, set quiet hours in the app and avoid early weekend mornings. Some manufacturers publish a guaranteed noise level in decibels on the listing; it's worth comparing if you live in a terrace with small, close gardens.
Connectivity and the app
Check Wi-Fi or mobile coverage where the charging station will go before you buy. Bluetooth-only models work fine but can only be adjusted when you're standing nearby, whereas Wi-Fi or 4G lets you pause mowing from work when a downpour is forecast. Read recent reviews of the app itself: it's the part of the mower you'll deal with every week.
Maintenance that makes it last
Blades: the forgotten consumable
Most robots use small pivoting razor-style blades. During the growing season, check them every 4-8 weeks and turn or replace them as needed. A blunt blade tears grass rather than cutting it cleanly, which leaves brown tips and encourages disease, even if the robot is out every day. Blades are cheap; make sure replacements for your model are easy to buy.
Cleaning the underside and wheels
Wet clippings build up fast on British lawns. Packed under the deck and on the wheels, they reduce grip on slopes and can cover sensors. A quick brush-down every couple of weeks prevents most navigation faults. Never use a pressure washer on a robot mower.
Winterising
Most owners bring the robot in for winter, typically from late October or November until March, depending on where you live. The grass barely grows below about 5 °C, and frost and long wet spells are hard on the battery and electronics. Clean it, charge it as the manual recommends and store it somewhere dry and frost-free, such as a garage or utility room. Our autumn and winter guide covers it step by step.
Checklist before you buy
- Area: your measured lawn against the model's rating, with 20-30% to spare.
- Navigation: boundary wire or wire-free, based on your lawn's shape, zones and tree cover.
- Slope: your steepest point, checked against the spec with a margin for wet grass.
- Narrowest passage: the width between lawn areas, and whether the robot fits through it.
- Safety: lift sensor, rain sensor, PIN and, if the garden is accessible from the street, GPS tracking.
- Connectivity: Wi-Fi or 4G coverage where the charging station will go.
- After-sales: a brand with UK support and easy-to-find blades and spares.
If you want a proven, low-risk starting point for a regular lawn of up to about 400 m², a wired model with the installation kit in the box, such as the Bosch Indego S+ 500, keeps things simple: its LogiCut system mows in neat parallel lines rather than at random.
Check the Bosch Indego S+ 500 on Amazon →
Keep reading
Best value robot lawn mowers → Best robot lawn mowers without a boundary wire → Husqvarna vs Worx vs Segway → All our robot mower guides →Frequently asked questions
What size robot lawn mower do I need?
Measure your lawn and choose a model rated for 20-30% more than its area, and more again if it slopes or is split into separate areas. A 150 m² lawn suits a mower rated around 250 m²; a 400 m² lawn, one rated 500-600 m².
Do I need to bury the boundary wire?
No. You can peg it on the surface and the grass will grow over it within a few weeks. Burying it a few centimetres deep protects it better from scarifiers, edging spades and moles.
How often should robot mower blades be changed?
Check them every 4-8 weeks during the growing season and turn or replace them when blunt or chipped. The small pivoting blades are cheap, and a sharp edge cuts cleanly instead of tearing the grass.
Can a robot mower cope with wet British lawns?
Yes, within reason. Choose a model with a genuine rain sensor, schedule mowing for the drier part of the day and allow extra slope margin, because damp grass and clay soil reduce grip considerably.
Should I run my robot mower at night?
No. In the UK it is best to mow in daylight only, because hedgehogs forage at night and are vulnerable to mower blades. Most apps make it easy to set a daytime schedule.