Replacing a fiberglass entry door You love your old, scuffed-up fiberglass door. It looks like home and, for all you know, has been saving you hundreds in heating and cooling costs for years. It's just too bad that door's been lying to you this whole time. Not only is a fiberglass door nearly three times as expensive as its steel counterpart, but it's also not doing your house any big favors. A $3,600 fiberglass door loses roughly 44% of its value the minute it's installed. A $1,000 steel door, meanwhile, isn't nearly as aesthetically pleasant, but retains 73% of its cost. At that rate, it's the most valuable single remodel you can do to your home. Bathroom addition This one's a really tough call families in one and one-and-a-half bathroom households struggle with every year once it's time to host holidays and family reunions. If you love your old home but would love it more of the folks who built it a century ago took 21st century personal space needs into account, the cost of another bathroom is probably the deciding factor. Even on the cheap, a 6-by-8-foot bathroom addition can cost upward of $40,000. While your family and visitors will no doubt appreciate it, it'll be underwhelming to homebuyers who've been looking at properties with the same number of bathrooms all day. A bathroom addition automatically drops 50% of its value, which means the $40,000 you spent to stop your family's ceaseless complaints tacks on only $20,000 to your selling price. Thanks for the $20,000 loss, kids. Backup power generator Emergency preparedness comes at a price, especially for worrywarts. Yes, there are some folks who live in areas of the country where the grid isn't all it could be and where power gets knocked out on a fairly consistent basis. Then there are those who lose power for a day and wonder how they're going to do their hair. The latter may not think dropping $15,000 for 70 amps of emergency power is a big deal and may dismiss the 53% of the investment that never makes it into a home's resale value. The former may want to reconsider paying $15,000 to get $7,000 if the only reason they're getting a generator is to prevent $30 in groceries from spoiling the next time a transformer blows.