A robot lawn mower costs roughly £45 to £90 a year to run on a typical UK lawn, once you add up electricity, blades and the battery spread over its life. Electricity is the smallest part of the bill. On a small garden it can be as little as £5 a year. Blades cost more than power over a season, and the battery is the one big cost, arriving once every three to five years. The exact total depends on your lawn size, your electricity tariff and the model you buy, so this guide works out the maths for a small garden and a large lawn separately, then compares the result with a petrol mower and a gardener.
Most buying guides quote the purchase price and stop there. That is the wrong number to judge a mower by. A robot mower lives in your garden for five to eight years, and the running costs over that time can add several hundred pounds. This guide covers every cost: electricity, blades, battery, boundary wire, data fees and winter storage, with the figures shown so you can redo the maths for your own tariff. If you are still choosing a model, our in-depth guide to robot lawn mowers for small gardens covers the features that matter most before you buy.
The short answer: what it costs per year
For a small UK garden of around 200 square metres, expect about £45 to £65 a year in running costs. For a larger lawn of around 800 square metres, expect about £80 to £120 a year. The purchase price is separate, and it is the biggest cost by far, but the running costs are low enough that a robot mower usually pays for itself against a gardener within two to four years.
The table below shows the yearly breakdown for each garden size. The figures are planning ranges, not promises, because tariffs and models vary. The battery line is the cost of one replacement battery spread across the years it lasts, which is how you should think about it when you budget.
| Cost | Small lawn 200 m2 | Large lawn 800 m2 |
|---|---|---|
| Electricity | £5 to £15 | £20 to £35 |
| Blades | £20 to £30 | £30 to £40 |
| Battery (amortised) | £20 to £40 | £30 to £50 |
| Wire, pegs and extras | £0 to £5 | £5 to £10 |
| Total per year | £45 to £65 | £80 to £120 |
The rest of this guide shows where each number comes from, so you can check it against your own garden and tariff.
Electricity: the cheapest part of the bill
Electricity is the cost most buyers worry about first, and it is the smallest line in the budget. A robot mower sips power. It has a small battery, a small motor and no engine to warm up, so a full charge uses a fraction of a kilowatt hour.
Expert Reviews worked out a real example for a small mower, the Yard Force EasyMow 260B. Its battery holds 2Ah at 20V, which is 40Wh per full charge, or 0.04kWh. Two outings a day use 0.08kWh. At the Ofgem price cap of 27.03p per kWh that applied in April 2025, that works out at about £5 of electricity for a full March to October season. A larger Husqvarna Automower 305E NERA uses about 7kWh a month according to its specifications, which is just over £15 for the same eight month season at the same rate.
Other UK guides land in the same range. Garden Ninja puts seasonal electricity at £15 to £25 for a typical lawn, and thebestmowers.co.uk puts it at £15 to £35 a year. The spread comes from lawn size and tariff, not from disagreement about the maths. Your tariff decides the exact figure, and the formula is simple: kilowatt hours used, multiplied by your unit rate in pence.
To work it out for your own mower, check the specification sheet for monthly energy use in kWh, multiply by the months in your mowing season, then multiply by your electricity unit rate. Most UK lawns need mowing from March to October, which is eight months. If your tariff is 25p per kWh and your mower uses 7kWh a month, the season costs £14. If your tariff is 30p, the same mower costs £16.80. The difference between a cheap tariff and an expensive one is a few pounds a year, not tens of pounds.
Two things push electricity use up. The first is lawn size: a mower that covers 800 square metres runs longer and charges more often than one that covers 200. The second is slope and thick grass, which make the motor work harder and drain the battery faster. Neither effect is large. Even a big lawn on a steep garden rarely pushes electricity past £35 a year.
One cost people forget is standby power. The charging station draws a small amount of electricity all year, even when the mower is parked for winter. It is only a few pounds a year, but you can cut it to zero by switching the station off at the socket once the season ends. That is also the right moment to bring the battery indoors, which matters for the next cost.
Blades: the real consumable
Blades are the cost that surprises new owners, because they cost more per year than electricity. Robot mowers cut with small, razor style blades mounted on a spinning disc. They shave a little grass every day rather than hacking through a week of growth, so the blades stay sharp for a while, but they still wear out.
Most manufacturers and UK guides agree on the interval: change the blades every six to ten weeks during the growing season. Garden Ninja gives six to ten weeks, thebestmowers.co.uk gives eight to twelve weeks, and aitoys.co.uk gives one to three months. The exact interval depends on your lawn. Sandy soil, twigs, pine cones and hidden stones blunt blades faster than clean, soft turf.
A set of replacement blades costs a few pounds. Garden Ninja budgets £20 to £30 a year for blades on a typical lawn, thebestmowers.co.uk quotes £8 to £20 per set, and aitoys.co.uk budgets £20 to £40 a year. For a small lawn, three sets a season at £7 to £10 each is a fair working figure. For a larger lawn, expect four sets, because the mower covers more ground and the blades wear faster.
Changing blades takes about five minutes with a screwdriver, and it is the one maintenance job you cannot skip. Blunt blades tear the grass instead of cutting it, which leaves brown tips and invites disease. If your lawn looks ragged after mowing, check the blades before you blame the mower. Cheap third party blades are widely available, but check reviews before you buy them: a blade that snaps or wobbles can damage the cutting disc, and that repair costs far more than the saving.
Budget £20 to £30 a year for blades on a small lawn and £30 to £40 on a large one, and treat it as the most predictable cost of ownership. It is the only running cost that arrives every single year without fail.
Battery: the big one-off cost
The battery is the largest single running cost, and the one most buyers forget to budget for. Robot mowers use lithium ion batteries, and like every lithium battery, they lose capacity over time. After three to five seasons, the mower will need charging more often, cover less ground per charge and eventually fail to finish the lawn.
Garden Ninja puts a replacement battery at £100 to £200 depending on the model, and gives a life of three to five seasons. Spread over four years, a £140 battery costs £35 a year, which is more than electricity and blades combined on a small lawn. That is why the battery line in the table above is the biggest single item.
How long your battery lasts depends on how you treat it. Heat and cold are the enemies. Leaving a lithium battery flat in an unheated shed through a British winter is the fastest way to kill it, according to Garden Ninja, and the advice from manufacturers agrees. The right routine is simple: at the end of the season, charge the battery, take the mower indoors or into a frost free garage, and store it somewhere dry. Check the charge once or twice over winter and top it up if it has dropped. A battery stored at full charge in a warm room lasts noticeably longer than one left flat in a cold shed.
Daily habits matter too. A mower that runs a little every day and recharges in small top ups puts less strain on its battery than one that is drained to empty and left for a week. Most models manage this themselves, returning to the station when the charge drops, so you do not need to do anything special. Just avoid letting the mower sit unused for months with a dead battery.
When the battery does need replacing, buy the genuine part or a well reviewed equivalent from a known brand. A cheap battery with the wrong capacity can shorten the life of the mower, and a badly made one is a fire risk. If your mower is still under warranty when the battery fades, check the warranty terms first: some brands cover the battery for two years, some for one, and some exclude it entirely.
Boundary wire, data fees and other extras
If you bought a wired mower, the boundary wire is a small extra cost. The wire itself lasts five to eight years according to thebestmowers.co.uk, and it usually only needs replacing if it is cut by a spade, an aerator or a mole. A replacement roll, pegs and connectors cost tens of pounds, and spread over the wire’s life, that is only a few pounds a year. Keep a spare length of wire and a few connectors in the shed, because a break stops the mower until you find the fault and join the wire again. Our guide to boundary wire vs GPS robot mowers explains the trade off in full, including which system suits your garden.
If you bought a wire free GPS mower, check for a data fee instead. Some GPS models use a network correction service to keep their position accurate, and some charge a subscription for app features or theft tracking after the first year. The fee varies by brand and is often free for the first year, so check the small print before you buy and add it to your yearly total if it applies. A mower that needs a mobile signal also needs a spot in the garden where the signal reaches, which is worth checking before the return window closes.
Winter servicing is the last extra. Some owners pay for a professional service once a year, which usually means a blade change, a clean, a software check and a battery test. It is optional on most models, and a careful owner can do the same work at home in half an hour. If you do pay for it, expect a modest fee that is far below the cost of servicing a petrol mower, because there is no oil, no spark plug and no air filter to change.
Worked examples: small garden vs large lawn
The numbers are easier to trust when you can see them worked out, so here are two complete examples.
Small garden, 200 square metres, wired mower. The mower uses about 5kWh a month over an eight month season, which is 40kWh a year. At 25p per kWh, electricity costs £10. Blades need three sets a season at £8 each, which is £24. The battery costs £120 and lasts four seasons, which is £30 a year. Wire and connectors add about £5 a year. The yearly total is £69, and the five year running total is about £345, plus the purchase price. That is the honest figure for a small garden, and it is less than two visits from a gardener.
Large lawn, 800 square metres, GPS mower. The mower uses about 12kWh a month over eight months, which is 96kWh a year. At 25p per kWh, electricity costs £24. Blades need four sets a season at £9 each, which is £36. The battery costs £180 and lasts four seasons, which is £45 a year. A data or subscription fee, if your model has one, adds to this, but the example assumes none. The yearly total is £105, and the five year running total is about £525. The bigger lawn costs more to run, but the cost per square metre falls, because the battery and the blades are shared across a much larger area.
Both examples assume the mower is stored properly over winter and the blades are changed on schedule. Neglect either habit and the totals rise: a ruined battery adds £100 to £200 in one year, and blunt blades add nothing to the bill but cost you the lawn.
Robot mower vs petrol mower vs gardener
Running costs only make sense in comparison, so here is how a robot mower stacks up against the alternatives.
A petrol mower is cheap to buy and expensive to run. It needs fuel, engine oil, a spark plug and an air filter, plus an annual service if you want it to start first time each spring. Guides that have done the maths put a robot mower’s electricity at less than a single tank of petrol for a rotary mower over a season, and the robot has no oil or spark plug to buy at all. The robot also mows little and often, which keeps the lawn healthier and removes the weekend chore entirely.
A gardener is the most expensive option by a long way. aitoys.co.uk puts a regular gardener at £25 to £40 per visit, and fortnightly visits work out at £650 to £1,040 a year. Against that figure, a robot mower’s £45 to £120 a year in running costs is small, and even the purchase price is recovered in two to four years for anyone who currently pays for regular lawn care. The comparison is not exact, because a gardener does more than mow, but for the mowing alone, the robot wins on cost by a wide margin.
The fair comparison is the petrol mower, and the robot wins there too on running costs, while losing on purchase price. A good petrol mower costs £200 to £500, a good robot mower costs £500 to £2,000, and the robot’s lower running costs take several years to close the gap. If you enjoy mowing and your lawn is small, a petrol mower is still the cheaper choice overall. If you want the lawn mowed without your time, the robot is the cheaper way to buy that freedom.
How to keep running costs down
Running costs are mostly fixed, but a few habits keep them at the low end of the range.
First, buy the right size of mower for your lawn. A mower rated for 1,000 square metres uses more power and wears its blades faster on a 200 square metre garden than a model rated for 300, because it is built for a bigger job. Our guide to the best robot lawn mowers for small UK gardens shows which models fit a small lawn without overspending on capacity you will never use.
Second, change the blades on schedule. Blunt blades make the motor work harder, which uses more electricity and drains the battery faster, so a £8 set of blades saves money in two places at once.
Third, store the battery properly over winter. Charge it, bring it indoors, and check it once or twice before spring. That one habit can add a full season to the battery’s life, which is the biggest saving on this list.
Fourth, keep the lawn clear of stones, twigs and toys. Every hard object the blades hit shortens their life, and a stone can chip a blade badly enough to need an early change. A quick walk around the lawn once a week is cheaper than a new set of blades.
Fifth, check your electricity tariff. If you are on a time of use tariff with cheap overnight power, set the mower to charge at night. The saving is only a few pounds a year, but it costs nothing to set up.
Verdict: cheap to run, dear to buy
A robot lawn mower is cheap to run and expensive to buy, and that is the whole story. Electricity costs £5 to £35 a year depending on lawn size and tariff. Blades cost £20 to £40 a year. The battery costs £100 to £200 once every three to five years, which works out at £20 to £50 a year. Add a few pounds for wire and extras, and the yearly total lands at £45 to £65 for a small garden and £80 to £120 for a large lawn.
Those numbers are low enough that running costs should not decide your purchase. The purchase price, the size of your lawn and whether you want a wire or a GPS system matter far more. If you want the full picture before you buy, start with our guide to the best robot lawn mowers for small UK gardens, then read our boundary wire vs GPS comparison to pick the system that suits your garden. Once the mower is in the garden, the running costs will take care of themselves, as long as you change the blades and look after the battery.
Frequently asked questions
How much electricity does a robot lawn mower use per year?
A typical UK robot mower uses 40 to 100kWh of electricity a year, depending on lawn size. At 25p per kWh, that is £10 to £25 a year. Small mowers on small lawns can use as little as £5 of electricity a season, according to Expert Reviews, while larger models use around 7kWh a month, which is just over £15 a season at the April 2025 Ofgem price cap of 27.03p per kWh.
How often do robot mower blades need replacing?
Change the blades every six to ten weeks during the growing season, which usually means three or four sets a year. Sandy soil, twigs and stones blunt blades faster. A set costs £8 to £20, so budget £20 to £40 a year depending on lawn size.
How long does a robot mower battery last?
Most lithium ion batteries last three to five seasons before capacity drops noticeably. A replacement costs £100 to £200 depending on the model. Storing the battery charged and indoors over winter, rather than flat in a cold shed, is the best way to reach the top end of that range.
Is a robot mower cheaper to run than a petrol mower?
Yes. A robot mower’s electricity costs less than a single tank of petrol for a rotary mower over a season, and it needs no engine oil, spark plug or air filter. The robot costs more to buy, so the saving takes a few years to cover the purchase price, but the yearly running costs are lower from day one.
Do robot mowers use electricity in winter?
Only a small amount, through the charging station’s standby draw, and only if you leave it plugged in. Switch the station off at the socket once the season ends, and store the mower and battery indoors. That stops the standby draw and protects the battery from cold damage.
