Robot mowers look absurdly expensive next to a petrol push mower at first glance. But a lawn mower isn't a one-time purchase — it's a five-year relationship with running costs, maintenance and your own time. When you total all of it, the gap narrows fast, and for some gardens the robot is genuinely cheaper.
The petrol mower's hidden running costs
The purchase price of a petrol mower is just the entry fee. Over five years you'll also pay for:
- Fuel every few weeks across the growing season, at prices that rarely fall.
- Oil changes and spark plugs to keep the engine healthy.
- Blade sharpening or replacement, plus air filters and the occasional carburettor clean.
- Servicing — most petrol engines want an annual service to last, and a missed one shortens their life.
- Winter storage faff: stabilising or draining fuel so it doesn't gum up.
None of these are huge alone, but they recur, and they add up to a meaningful sum over five seasons.
The robot mower's cost shape
A robot front-loads its cost into the purchase, then runs cheaply. Its ongoing costs are electricity (pennies — these draw very little), small blade swaps (the blades are cheap razor-like tabs you change every month or two), and occasional part replacements over the years. There's no fuel, no oil, no annual engine service. The two real risks are the upfront price and, eventually, a battery replacement — though good packs last many seasons.
The cost nobody puts on the spreadsheet: your time
Here's where the comparison really tilts. A petrol mower asks for an hour or two of your weekend, every week, all season — call it 25-30 sessions a year. A robot mower asks for setup once and a few minutes of upkeep thereafter. If your time has any value at all, those reclaimed weekends are the largest line item in the whole calculation, and they fall entirely on the robot's side.
So which actually wins over five years?
- Small, simple lawns: the petrol (or battery push) mower usually wins on pure cash — running costs are modest and the robot premium is hard to recoup.
- Medium-to-large lawns: the robot's low running costs plus the value of dozens of reclaimed weekends typically close or reverse the gap by year three or four.
- Anyone who values a consistently short, healthy lawn: frequent light robot cutting also improves the grass, a benefit no spreadsheet captures.
Run the numbers against your own lawn size and how much your weekends are worth. Compare current models on price and running cost in robot mowers, see our top-rated picks, or read whether one suits your garden in our buying guides.
