Free tool
Robot mower running costs calculator
Pick a mower, enter your lawn size and electricity price, and the calculator estimates a year's running costs: electricity for charging and standby, replacement blades, any subscription and servicing. Every assumption is shown and can be changed.
How to use the calculator
- Choose a mower. Every current version we track is in the list. Discontinued models aren't included.
- Enter your lawn area in square metres. If you don't know it, use the lawn size calculator.
- Enter your electricity unit rate in pence per kWh. The default is 25p. For current rates, see Ofgem's energy price cap page, or use the figure on your bill.
- Add any subscription or servicing you expect to pay each year. Both start at zero.
- Press Calculate.
The assumptions
Open Advanced assumptions to change any of these.
- Battery size comes from the manufacturer's specification. If it isn't published, you'll be asked for it.
- Charges per week are worked out from how much of the mower's rated area your lawn uses. A mower mowing its full rated area is assumed to charge about once a day (7 a week). A smaller lawn needs proportionally fewer charges, with a minimum of 2 a week.
- Mowing season is 32 weeks, roughly March to October.
- Charging efficiency is 85%: for every 0.85 kWh stored in the battery, about 1 kWh is drawn from the wall.
- Standby is 2 W for the charging station, all year round. That adds about 17.5 kWh a year.
- Blades: 3 sets a year by default, priced from our accessory data for that model. If we don't have a UK blade price, £15 a set is assumed and the result says so.
Reading the result
The total is split into electricity (with the kWh figure), blades, subscription and servicing, so you can see what drives the cost. For most models, blades and any subscription will matter more than electricity.
The figure leaves out one-off and occasional costs such as a replacement battery, a garage, installation or repairs outside warranty. Our guide to robot mower costs covers those.
Frequently asked questions
Why is the electricity cost so low?
Robot mower batteries are small, usually well under 1 kWh, so even charging most days through the season uses modest amounts of electricity. Blades, subscriptions and servicing often cost more over a year than the power does.
What electricity price should I use?
Use the unit rate on your latest bill. The calculator starts at 25p per kWh as a round default, but rates change every quarter. Ofgem publishes the current price cap unit rates.
What if the manufacturer doesn't publish the battery size?
The calculator tells you and leaves electricity out until you enter the capacity yourself. If you know the battery's voltage and amp-hours, multiply them to get watt-hours: an 18 V, 5 Ah battery is 90 Wh.
Does it include the cost of 4G data?
Only if you enter it. Some manufacturers include a few years of data and then charge, and some models need no subscription at all. Check the model page, then type the yearly cost into the subscription box.