Electric power is becoming part of more areas of everyday life, from cars and bikes to tools and garden equipment. Robot lawn mowers are another example. Instead of using a petrol engine, they typically rely on a rechargeable battery to power an electric motor, cutting system and navigation equipment.
For homeowners, the appeal is not simply that the mower runs on electricity. A robot mower can also operate on a schedule, return to its charging station when needed and handle regular cutting without someone having to push it around the garden.
But there is a more useful question to ask before buying one: how much electricity does a robot mower actually use?
The answer depends on factors such as lawn size, mowing frequency, terrain and the mower’s battery capacity. Looking at these numbers can give homeowners a better idea of the potential running cost and whether a battery-powered mower makes practical sense for their particular lawn.
In other words, the important figure is not just how advanced a mower is, but how much energy it needs to keep the lawn maintained.
How Much Electricity Does a Robot Lawn Mower Need?
The electricity used by a robot mower depends less on its battery size alone and more on how often it operates. A mower may charge several times during a week, depending on lawn size, mowing schedule, terrain and grass growth.
Manufacturers and independent tests often report energy consumption in different ways. Some specify battery capacity in Ah or Wh, while others provide estimated monthly electricity use. For example, some robot mower specifications list monthly consumption of around 5–12 kWh for lawns of roughly 400–700 m².
It is important to distinguish battery capacity from electricity drawn from the mains. Battery energy is calculated from voltage and amp-hour capacity: Wh = V × Ah. The electricity taken from the wall can be higher because charging involves energy losses, while the charging station may also consume some power when the mower is idle.
For this reason, a larger battery does not automatically mean higher electricity costs. The more useful figures to consider are how much energy the mower uses per mowing cycle, how frequently it needs to recharge, and how much electricity it consumes over a typical month or year.
What Affects a Robot Mower’s Energy Consumption?
A robot mower’s electricity use is influenced by several factors, so two gardens with the same lawn area can have different energy requirements.
Lawn size is the starting point. A larger mowing area generally requires more operating time and potentially more charging cycles. However, the manufacturer’s maximum lawn-area rating should not be treated as the amount of electricity the mower will always use. Actual coverage also depends on how much time the mower can operate each day.
Terrain also matters. Slopes, uneven ground and frequent turns can increase the power required to move the mower. A mower working on a flat lawn may therefore use less energy than the same model operating on a more demanding garden.
Mowing frequency affects total consumption. During periods of fast grass growth, homeowners may schedule more frequent mowing. More operating hours naturally mean more charging over the season. Weather, grass growth rate and the desired cutting height can all influence the schedule.
Finally, obstacles and garden layout can affect efficiency. Trees, flower beds, narrow passages and multiple lawn zones can require additional navigation and travel. This is why the actual electricity consumption of a robot mower is better judged over several weeks or a full season rather than from battery capacity alone.
Battery Size vs Lawn Size: What Do the Numbers Tell You?
Battery capacity is useful for comparing robot mowers, but it should not be treated as a direct measure of electricity consumption. A battery’s capacity is normally expressed in mAh, while energy consumption is better measured in Wh or kWh. Without knowing the battery voltage, mAh alone cannot tell you how much energy the battery stores.
For example, ANTHBOT lists the following battery capacities and recommended mowing areas:
| Model | Recommended Lawn Area | Battery Capacity |
| ANTHBOT M5 | Up to 500㎡ | 2,500mAh |
| ANTHBOT M9 | Up to 1,000㎡ | 5,000mAh |
| ANTHBOT N8 | Up to 1,500㎡ | 9,200mAh |
The figures show a general relationship between mowing area and battery capacity, but they do not mean that the N8 will necessarily use several times more electricity than the M9. Actual consumption depends on operating time, mowing frequency, terrain, grass conditions and charging losses.
For homeowners, the more useful approach is to look at actual electricity consumption over time. Tracking how many times the mower charges and how much electricity is drawn from the household supply can provide a much more realistic picture of annual running costs than comparing battery capacity alone.
What About Charging Cost in the UK?
For UK homeowners, the easiest way to estimate a robot mower’s electricity cost is to multiply its annual electricity consumption by the household’s electricity rate.
From 1 October to 31 December 2026, Ofgem’s average electricity unit rate for households on standard variable tariffs paying by Direct Debit is 26.32p per kWh across England, Scotland and Wales. Actual rates vary by region, tariff and payment method.
The calculation is straightforward:
Annual charging cost = Annual electricity consumption × Electricity price
For example:
| Annual electricity use | Approx. cost at 26.32p/kWh |
| 20 kWh | £5.26 |
| 40 kWh | £10.53 |
| 60 kWh | £15.79 |
| 100 kWh | £26.32 |
These figures are only examples rather than typical robot mower consumption figures. Actual costs will depend on the mower, lawn size, mowing schedule, charging efficiency and electricity tariff.
It is also worth remembering that the standing charge on an electricity bill is not a robot mower cost. It applies to the household electricity supply regardless of whether the mower is being charged. For a realistic estimate, homeowners should therefore focus on the additional kWh consumed by the mower.
ANTHBOT M5: A Compact Example
The ANTHBOT M5 provides a useful example of how battery size and lawn coverage come together in a compact robot mower. It is designed for lawns of up to 500㎡ and uses a 2,500mAh battery. Its 20cm five-blade cutting disc and compact design are intended for smaller lawns and narrow passages.
The M5 uses Full-Band RTK + Dual Vision for navigation and does not require a boundary wire. It can also create mowing schedules and be controlled through the app. These features can affect how efficiently the mower covers a lawn, particularly where the garden contains narrow areas or obstacles.
For energy consumption, however, the 2,500mAh figure alone is not enough to calculate the mower’s electricity cost. Users would also need the battery voltage, charging efficiency and actual operating time. Tracking the mower’s charging cycles and electricity consumption over a typical week would provide a more useful real-world figure.
In practice, this illustrates why lawn coverage, battery capacity and actual electricity consumption should be considered separately when comparing robot mowers.
Is a Robot Mower Actually More Efficient Than a Conventional Mower?
Comparing a robot mower with a conventional petrol mower is not simply a matter of comparing electricity with fuel. The two machines operate differently: a conventional mower usually completes a lawn in one session, while a robot mower cuts smaller amounts of grass more frequently and may return to its charging station several times.
Energy studies have found that battery-powered mowing can require substantially less primary energy than petrol-powered mowing under comparable test conditions. One study comparing battery and gasoline rotary mowers found primary energy requirements of 5.47–9.32 kWh/ha for the battery mower, compared with 48.21–51.42 kWh/ha for the gasoline mower, depending on the grass type.
However, energy efficiency is only one part of the comparison. A petrol mower requires fuel and routine maintenance such as oil and filter changes, while an electric robot mower mainly requires electricity, blade replacement and battery maintenance over its service life. Consumer Reports also notes that electric mowers generally have advantages in noise and maintenance, although petrol models can have an edge in some cutting-performance tests.
For homeowners, the more useful comparison is therefore total running energy and maintenance over a mowing season, rather than simply asking which machine has the larger motor or battery.
The Useful Number Is Cost Per Lawn, Not Battery Size
Battery capacity is useful when comparing specifications, but it does not tell you the actual cost of running a robot mower. A better approach is to track electricity consumed per week or month, then calculate the cost based on your local electricity rate.
For a more complete ownership picture, homeowners can also include replacement blades, battery replacement, routine maintenance and any installation or connectivity costs. These costs can vary significantly depending on the mower and how heavily it is used.
A simple calculation is:
Annual running cost = Annual electricity consumption × Electricity rate + Maintenance and consumables
Keeping a record for the first mowing season can give you a much more realistic estimate than relying on the mower’s battery capacity or advertised lawn size. It also makes it easier to compare a robot mower with a conventional electric or petrol mower based on your own lawn, electricity price and mowing habits.
Ultimately, the useful question is not simply “How large is the battery?” but “How much does it cost to keep my lawn maintained?”
