I'm new too but have been working on a similar problem; you might like to consider if it could apply to you. We moved to this place 6 years ago, 1/2 an acre with small house. It was 90% grass, as my wife said: "a kikuyu desert". We mowed it with a 13hp ride on. Since then we have replaced much of the grass with trees, shrubs and ground covers, with lots of mulch, bounded by lawn edging, so we now have only 30% grass. The edging is curved and irregular and the grass looks stunning, winding away through the woodland, which I believe is doing a lot to remove CO2 in the first place, plus we now use an ordinary petrol powered, push mower, using much less fuel.
I won't be able to continue pushing the mower many more years, so would like to find an electric, self propelled machine. So far I have found one in the USA at http://www.solarispowerproducts.com/index.htm
but nothing in Australia, so need to consider whether to import one or to electrify a S/H petrol one. I love the mulching capability on my present machine, so need the extra power to do that.
I did find this electric ride on in Australia, 3 motors: one for drive and two for cutter blocks. 3 hour run time. Is it believable? http://www.neproductsdirect.com.au/p/59 ... e-300.html