You underestimate the cost of batteries. The Ryobi 80V 10AH batteries are $899 ea, and the 40V 12AH are $359 ea. The 54" mower uses 3 of the 80V and 4 of the 40V, Total replacement cost is $4133. Warranty is 5 yrs. Some here have reported Ryobi battery life of 3 yrs, some over 6 yrs. 5 yrs is a good estimate. So... $4133 is $826.60 per year. If used for the typical homeowner usage of 40hrs/yr, that works out to $20.67/hr. At 50 hrs/yr, that works out to $16.53/hr of operation. If we give the Ryobi the benefit of 7 yrs of battery life at 50 hrs/yr, that works out to $11.81/hr of operation. I did a similar calculation for my 54" commercial mower. It uses about 1 gallon of E0 ($3.80) per hr. I figure about $50/yr avg in maintenance for oil changes and air filter servicing/replacing. The air filter doesn't need replacing every year. I use my mower about 40 hrs/yr, which works out to $5.05/hr of operation. I was wrong before when I said that it cost me $5/mow. I had forgotten maintenance. My mowing takes 1.5-1.75 hrs, which works out to $7.57 - $8.84 per mow.
Of course, these costs would be less for yards smaller than mine.
I think that it's disingenuous to promote the economy of battery mowers by citing only the cheapest part of the TCO... the cost of the electricity. Battery mowers DO have advantages, but cost is not one of them. Note that I didn't even include purchase price in my cost analysis above.
