The Sunseeker S4 is the robot mower for trees, not the mower for every lawn.

Maximum coverage 0.25 acre

Navigation 3D LiDAR and Vision AI

Cutting width 7 inches

Cutting height 1.6–3.2 inches, manual dial

Battery 20V, 4Ah lithium-ion

Drive and slope Rear-wheel drive, up to 42% or 22°

Price bracket Step-up

Our Verdict

Buy the Sunseeker S4 for a shaded, clearly bounded lawn no larger than a quarter acre, but choose something else for open acreage, abrupt terrain or genuinely hands-off edge care.

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Most wire-free robot mowers replace a boundary cable with an RTK antenna that still needs a useful view of the sky. The S4 removes both pieces of infrastructure. Its rotating LiDAR dome reads the yard from the mower itself, which is why it keeps its bearings beneath trees, beside buildings and under eaves that can unsettle satellite-dependent machines.

That distinction is the whole review. The S4 is unusually good at knowing where it is, yet only average at getting its narrow, two-wheel-drive body through everything a lawn can put in the way. It cuts cleanly and resumes work after charging, but its central seven-inch deck leaves trimming beside vertical borders, its battery turns a larger job into several sessions, and there is no cellular or GPS radio for tracking away from Wi-Fi.

LiDAR is the point, not the garnish

A straightforward installation needs a level dock near power, Wi-Fi for pairing and enough clear space for the mower to approach. Automatic mapping can trace an obvious perimeter, while manual steering is better around curved beds, indistinct property lines, drops and roads. Allow time for charging, firmware updates and map corrections rather than treating “setup in minutes” as a promise of an immediate first mow.

The resulting map is more than a decorative app screen. The S4 can divide a property into zones, join them with corridors, set no-go areas and vary schedules or cutting direction. Its straight-boundary tool is particularly useful where two lawns meet without a physical border. A virtual corridor cannot open a gate, however, so fenced front and rear lawns still require somebody to provide access.

LiDAR also has a less obvious limit: it needs features to locate itself against. Fences, trees and buildings make a compact yard legible, while a broad, featureless field can be a worse fit despite falling within the nominal acreage. That is why the S4 belongs among the best choices for yards obstructed by trees and buildings, not among machines for open acreage.

The app supplies live mapping, schedules, per-zone settings, work logs, mowing speeds, direction control and decorative patterns. What it does not supply is cellular fallback, native GPS tracking or a granular obstacle-sensitivity slider. Yard-wide Wi-Fi may therefore matter more than the broadband speed entering the house.

Sunseeker S4, view 2

Sunseeker S4, view 3

Sunseeker S4, view 4

Sunseeker S4, view 6

Sunseeker S4, view 2

Sunseeker S4, view 3

Sunseeker S4, view 4

Sunseeker S4, view 6

It cuts beautifully, then takes its time

Once short grass is under control, the six-blade floating disc leaves an even surface and disciplined parallel lines rather than the wandering tracks of an old random-navigation mower. The alternating “traceless” direction is the sensible default for repeated use because it prevents persistent wheel grooves and closes the occasional narrow row left between passes.

The mower is a maintainer, not a reclamation tool. Tall grass and dandelion stalks can look like obstacles to its cautious sensing, causing it to route around the very growth it should cut. Start with a conventional mow, keep the lawn below roughly three inches during setup, and schedule the S4 often enough that weeds never become landmarks. Marking an entire lawn as a safe zone can suppress false avoidance, but doing so also weakens the protection around real objects and is not a substitute for clearing the yard.

The quarter-acre rating is not a one-charge promise

Expect about 90 minutes of mowing from the 4Ah battery before an approximately 80-minute recharge under favorable conditions. In one representative cycle, the S4 covered 76% of a main zone in 83 minutes; another 0.2-acre lawn required two returns to the dock. It reliably charges, leaves again and resumes where it stopped, so elapsed time is mostly harmless until a gate, pets or a narrow operating window requires supervision.

Edges remain the honest drawback

The edge mode can produce a tidy result where the mower is allowed to overlap flat paving, which explains the strong reports from open sidewalks and driveways. A wall or fence exposes the geometry: the central cutting disc sits about 4.3 inches inside the housing, so grass beside a vertical boundary cannot reach the blades. Abrupt humps and conservative mapping can make the remaining strip considerably wider. Keep the string trimmer.

Good avoidance does not make the lawn childproof

The S4 gives obvious objects such as balls, rocks and tools a generous berth, and its bumper and lift shutdown provide useful secondary protection. Low waste, thin sticks, hoses and small wildlife remain poor candidates for blind trust. Clear the lawn and keep children and animals out of the working area even though the mower is technically quiet enough and its active LiDAR bright enough to operate at night.

Rear-wheel drive copes well with rolling ground and broad moderate slopes, but the 42% rating does not describe every transition. A small grass-to-pavement hump or sharp planter dip can strand it even on an otherwise flat lot. For broken ground and severe inclines, an AWD mower selected for steep, uneven terrain is the safer purchase.

The price can change the verdict

The S4 has appeared at sharply different advertised prices, so a price-independent recommendation would be dishonest. At a substantial discount from full list, its accurate LiDAR mapping, clean cut and automatic resume make a persuasive package. Near full list, the narrow deck, modest endurance and missing GPS and cellular radios are too expensive to excuse.

The TerraMow V1000 is the stronger endurance and connectivity alternative, with a wider deck, longer working time and GPS and cellular hardware, although the S4 carries the higher stated slope limit. The ECOVACS GOAT O1000 LiDAR PRO is the better comparison for edge-conscious buyers because it adds a trimming mechanism and app-controlled cutting height; the S4 counters with a better manual-mapping interface and more conservative obstacle behavior.

Within Sunseeker’s own range, the choice is simpler. The X5 trades the S4’s antenna-free LiDAR for AWD, greater coverage and stronger slope ability, while the X7 moves farther toward large, steep properties. Choose the S4 only when small-yard navigation beneath trees matters more than traction or throughput.

The mower does not eliminate lawn maintenance

The maintenance burden is modest but real. Keep the LiDAR dome and front camera clean, clear compacted clippings from the disc, and inspect the six razor blades rather than waiting for torn grass tips. The published schedule calls for disc cleaning after 60 operating hours and blade replacement after 120 hours, although coarse or fast-growing turf may dull them sooner.

The mower uses a 20V, 4Ah lithium-ion battery, but there is no confirmed S4 replacement part number, procedure or model-specific replacement cost in the available record. General battery guidance suggests planning for eventual replacement after several years, not assuming the original pack will last for the mower’s entire life.

The dock includes a small overhang for the LiDAR area, not a full shelter. Sunseeker sells an S4-specific garage separately, and garages intended for the X5 or X7 do not fit. The mower carries an IPX6 rating, but that means resistance to water jets rather than floods: rain and fog can disrupt LiDAR ranging, and standing water can disable the machine, so severe weather and winter storage belong indoors.

Support replies have been quick, though the technical quality of those replies has varied. Direct-store return language is also stricter than the prominent 30-day badge suggests once a mower has been opened, making retailer-specific return terms worth checking before the yard becomes the experiment.