Well, I don’t rightly know, yet. What I can tell, a new roof, which should last anywhere from 15-20 years is about $3500 for a 2000 sq foot (or so) multi-level home. OK, so that is a good number to keep in mind.
How about a furnace? Well a good High efficiency (not SUPER high efficiency) natural gas furnace with installation, should cost around $4000 or less (would be my guess). A neighbour of mine (who is a self-described obsessive engineer who enjoys numbers) figures it is not worth getting the ULTRA SUPER WAKA WAKA furnace, because it doesn’t save you that much, but his reckoning is that a High Efficiency furnace will pay for itself in about 5-7 years, if you compare it to a furnace from about 15 years ago (Natural Gas that is). I guess we’ll see if that is the case.
Air Conditioner? Well tack on another $4000 for a good enough one for an over 2000 square foot home (installed). Comparisons, well my current air conditioner turns on around 10:00 AM on a hot day and turns off at about 11:00 PM (without shutting off). My guess is this new unit will save me some money (maybe not pay for itself, but my electricity bill should be less).
Windows? Another good question. The guy I spoke to at Home Depot said, depending how easy it is and how much work and repair need to be done, installation of a window could be from 50% of the price of the original window (so a $500 window would cost $250 to install) all the way up to 300% of the cost of a window (so a $500 window would cost $1500 to install). My house needs a lot of work, so let’s budget about $7500 for windows for now.