15 * 3.5 = $52.5 a year
40 * 3.5 = $140 a year
It is important to realize that the payback for some of these improvements take a while.
This is Gloria. I couldn't wait to put in my two cents about the furnace. It's so nice to not have to worry about CO poisoning from a 15 + year old furnace with no cover. Or worse the potential fire hazard was astronomical. It's definitely one worry this stay-at-home mother doesn't have to constantly worry about. I personally don't even care about the financial payback...because the stress-free-ness of the situation is worth much more.