Annual robot mower running cost is electricity plus consumables, recurring services and repairs paid during the year. There is no useful single total without a mowing season, utility rate, blade system and service plan. A battery replacement can make one year’s spending very different from the next.
Reviewed September 28, 2026. The worksheet below uses explicitly hypothetical prices and usage. It is not a measured operating-cost test, a current price survey or a forecast for a particular mower.
Start with energy, not charger wattage
Electricity is billed in kilowatt-hours (kWh). A charger’s maximum power rating does not say how much energy the complete mower-and-station system uses over a week: it does not draw that maximum continuously.
For a documented example, Husqvarna lists 8 kWh per month at maximum use for the UK Automower 310 Mark II. Keep the “at maximum use” condition attached to that figure. Do not present it as a measured monthly result for a smaller lawn or another model.
For your own baseline, record energy at the station’s supply over a representative period that includes both mowing and charging. Use a compatible energy monitor only where its electrical and weather protection are suitable for the installation; do not put an indoor meter into an exposed outdoor outlet. Include a separately powered reference station if your installation has one.
Season electricity estimate = measured kWh ÷ measured calendar days × powered days in the season × applicable cost per kWh.
Use powered days, not just days on which the blades turned, if the measurement includes waiting and charging. If equipment stays powered outside the mowing season, estimate or measure that consumption separately. For time-of-use billing, price each period at its applicable rate. Fixed household account charges are not automatically additional mower costs.
A complete worked example
Every input in this example is invented for the calculation. All amounts use one hypothetical dollar currency; replace them with your own currency, bills and quotes.
| Item | Assumption and calculation | Annual amount |
|---|---|---|
| Electricity | 1.4 kWh in 7 days ÷ 7 × 210 powered days × $0.20/kWh | $8.40 |
| Blades and required screws | $24 pack supplies 4 complete changes; 6 changes × $6 | $36.00 |
| Selected subscription | $30 per year | $30.00 |
| Booked service | One $60 service | $60.00 |
| Scheduled running total | Sum of the four items | $134.40 |
The blade example assumes a pack that really supplies four full changes, including the required fasteners. Count changes, not individual blades: a 12-blade pack is four sets only for a machine that uses three blades per change. This is a consumption budget; buying two whole packs would put $48 on that year’s receipts and leave two changes in stock.
In this example, doubling the electricity rate to $0.40/kWh raises the energy line to $16.80, an increase of $8.40. Adding a $120 repair raises cash spending by the full $120. That comparison shows why electricity alone is an incomplete ownership budget; it does not predict the likelihood of a repair.
Keep a battery allowance separate from a bill
Suppose a compatible installed replacement costs a hypothetical $180. Choosing to reserve $60 a year over three years would bring the example’s planned budget to $194.40. Three years is a budgeting assumption, not a promised battery lifespan.
In a year when you actually buy the battery, record the $180 payment. Do not count both that payment and the $60 allowance as cash spent on the same replacement. Our battery-life guide separates useful runtime, ageing and charging faults.
Fill in these items for the mower you own
| Budget line | Evidence to collect | Your amount |
|---|---|---|
| Electricity | Dated kWh reading, measurement period, season length and utility rate | Fill in |
| Blades and fasteners | Correct part number, sets per pack, invoice and changes used | Fill in |
| Connectivity or tracking | Included term, renewal date and current renewal quote; mark zero only if confirmed | Fill in |
| Routine service or storage | Written scope showing included labor and parts | Fill in |
| Unscheduled repairs | Paid invoice, recorded separately from the routine baseline | Fill in |
| Battery replacement | Actual payment, or a clearly labeled future allowance | Fill in |
A blank amount means you have not established it; it is not zero. Avoid double-counting blades that are already included in a service package. Include shipping and taxes consistently when comparing quotations.
Running cost versus total ownership cost
To compare two purchases, add the mower, installation, optional navigation hardware and initial accessories to the same chosen ownership period. Keep your expected running costs, repair scenarios and remaining resale value explicit. Do not quietly spread one model’s purchase price over five years and the other’s over ten.
There may also be work left for you: edge trimming, cleaning, seasonal setup and retrieving the mower. Record time separately from cash unless you deliberately assign an hourly value. Our buying guide helps identify installation and coverage requirements, while the blade guide helps establish the correct replacement set.
Update the worksheet from receipts at the end of the season. If spending rises, first identify which line changed—tariff, operating time, parts, subscription or repair. A larger bill alone cannot diagnose a corroded connector, failing battery or motor fault.
Update — September 28, 2026: Rebuilt the cost example with explicit hypothetical inputs and separate consumption, cash and battery allowances.