I've got the expand-it tiller... it's fine for seedbeds and a bit of inter-row weeding but it's not a rotavator.... I can't imagine a 1hp electric is any better.... remember you need about 70 amps at 12V to get a horsepower out of the electric ones.... and you'd need a decent inverter too..... I'd use petrol every time... A jumpstarter would only run it for a few seconds before it got too hot, you're looking at a couple of car battery sized liesure batteries to do anything significant, car batteries wouldn't be up to it, they're not built to be drained like that....
So say 80 quid for the inverter, another 100 or so for the liesure batteries adn you'd want a good charger to plug them into back home so another 20 or so..... say 200 quyid to be able to run the electric one for a couple of hours.... or carry a fuel can and use the expand-it... which can also be the strimmer (very useful), pruner, path mower etc etc.....
chrisc
chrisc