Another rip off!
For those not familiar with "Green Deal" the principle is that if there's "renewable generation" involved, or energy saving possibilities (from a goverment approved list), you can have your property assessed by a government approved assessor, borrow the money to have work done (by government approved suppliers only), and then have your super-competent energy company take the money off you, including interest over the life of the asset. It'll be more expensive than adding the debt to a mortgage, cheaper than a personal loan, and be available to tenants in the same way. If you move house the debt is supposed to stay with the property, but there is some form of recourse to the householders in some situations, so be warned.
Problem is, this replaces CERT and CESP schemes that at the moment are offering free cavity and loft insulation for most eligible people, and additionally some support vulnerable customers (because that's not the job of the welfare state, is it now?). CERT and CESP are funded from a circa 15% rake off of your energy bill, but at least the money goes back to consumers. At the end of this year, those schemes stop, and if you want cavity wall or loft top up insulation (current standards are around a foot on insulation in the loft) you'll be paying the full wack. SO IF YOU WANT THOSE DOING FREE OR DISCOUNTED, ACT NOW - you don't need to get your own energy supplier to do it, just phone round all of them, and go with a name you're happy with).
Of course, the 15% rake off will continue - but that's now being hoovered up by DECC's stupid feed in tarriffs, in small part supporting middle class eco-twerps, but much more significantly all the government's subsidies for crap like wind power. I expect the lower end of the home improvements market to mis-sell crappy home "improvements", leaving the gullible out of pocket, to boot, in the same way that solar panels have thus far often been mis-sold. For some improvements you will also have to contribute up front if the energy savings won't pay for it all (eg in the case of double glazing).