Thanks for the responses

I'm still very much in two minds. I guess I know I would be happier in the short term if i quit but I don't know if i will regret it in the future. I'm just not sure what a phd will do for my career, it might get me a job i can't imagine yet or it might be completely useless.

I'm also having a tough time seeing quitting the phd as anything other than a failure.. I know i shouldn't think like that but i can't help it.

I'm hoping someone can give me some advice as i'm going round in circles. I'm currently a 2nd yr phd student in theoretical physics (cosmology) and am looking at another 2yrs to go. I have not been working very well so far, I have little motivation and a supervisor who is not much help. I have been thinking about quitting for 8 months but didn't want to quit before knowing what to do next. Recently I found a masters course in renewable energies and am really interested in this area. I was all ready to quit but after speaking to some engineers they all said that a phd (even in a completely different field like cosmology) will probably put me in better stead. So now i'm unsure about whether I should quit and do a msc in something I enjoy and want to get into or carry on with this phd (painfully) for the next 2 yrs in the hope that a phd in anything will land me the ideal job in the renewables sector.

what do you think? I don't hate my phd but I have become much more interested in other more relavent things.

Any advice is appreciated