Don't know the best deal and I still think it is questionable of...

Don't know the best deal and I still think it is questionable of the real economic value they provide. There are plenty of dodgy deals out there the be wary of.

It is certainly something I am thinking of doing for my rentals but it is about finding the right combination of economic circumstances to make it worth while. My biggest concern is despite the slated lifespans of the items will they really last that long as you will need them too to make a decent return on your investment. Then you have to also consider any annual maintenance, extra insurance costs etc.

If you are interested one site I regularly look at is:
http://www.energymatters.com.au/