They are probably not quite powerful enough for ordinary farm work - ours are a bit faster, and they are sometimes used for more than the 30 miles this one can do. And you'd have to put them on charge every night.
I believe there is a diesel version that's supposed to be more environment friendly - maybe you could run that off old cooking oil, too. And whatever the fuel, they are not toys. There was a fatal accident near here not long ago - not a farm vehicle, but somebody racing along the road. Should always be used with a helmet on (but that's not COOL, is it

?), you must never take a passenger (unless you have one of the rare versions that are specially designed for taking passengers), and you must make sure your trailer isn't overloaded, which happens sooner than you think. Lots of accidents happen on farms, too. Lots of kids involved. Oh, and you should keep your bum on the seat when you are driving - which again just isn't cool enough for your average male young(ish) farm worker. Why is it that my younger male colleagues always ride standing up? It's so easy to lose your grip on it if you hit a large stone or a pothole - and show me the farm that isn't full of them! (I should know - tripped over a stone last year when getting off the quad to open a gate - and couldn't walk properly for a couple of months!)
Saying that, I really enjoy being out on them! They take you to places that cars can't go, and that would be rather hard to walk to (especially if you are carrying bags of feed/sick lambs).