Electric lawn mowers, either corded or cordless, are the sane choice if you have grass to cut (short of finding a way to replace it with native plants that don't need to be cut – something I've been interested in lately; anybody has tips?). They are not quite as eco-friendly as these, but certainly more practical, and more importantly, a lot less polluting than the gas-powered versions (not to mention less noisy). Because of the polluting nature of gas mowers ("A conventional mower produces as much pollution in one hour as 43 late model cars or driving 340 miles, say industry experts."), many exchange programs where you can get either a rebate or a new electric mower for your old gas one exist. Keep an eye open for those in your area.