This article from GreenBuildingAdvisor.com shows why calculating the payback cost on a green home does not give you a complete or reliable picture on the benefits of green appliances and technology. The first reason why payback is distracting is the fact that it tends to take the total cost of the item divided over how long it takes to pay for itself when, in a situation where the appliance purchase is necessary, it is more relevant to determine how long it will take to pay for the cost difference between the appliance and the less efficient alternative. Viewed in this way, the investment in the green model sells itself much more powerfully.
Read the full article here: When You’re Financing a Green Home, Payback is Irrelevant