We have a gasoline generator big enough to run the house- it’s not natural gas (can’t get that here)
but we have a big freezer full of food, and are old enough to appreciate lights rather than candle light. We do get power outages regularly, but they are usually short. It’s not portable…my husband likes big, old, and cast iron so it’s an old Onan that weighs about a ton andis permanently installed 9n the shop, of course)
Our friend the realtor says it would be a positive selling point. It’s already saved enough meat to pay for itself. But it was about 3K with the parts and wiring etc.
I’m a realtor in NW Indiana, where we have storms in every season that can potentially knock out the power. Lots of people have generators of all kinds, but I have never one add value to a house. It may be a “ooo…that’s nice feature” but never did it justify spending any more money, especially $8-10 thousand dollars. That’s the kind of added value you see in a remodeled kitchen or a new master suite.
It also depends on how disruptive a person considers a power outage to be.
I don’t think you’d get any extra money out of it, but if both houses in the OP were for sale at the same time, and there was only one buyer, your house would probably get the offer.
It depends on where you live. In locations where power outages are common it adds more. Of course, smaller systems that protect only specific critical circuits are a better investment.
Yes, and that’s probably in part geographical. As I posted above, a lengthy outage in winter can lead to frozen and burst pipes, which can be catastrophically expensive. In a milder climate, assuming you’d have someone or someplace you can take the contents of your fridge or freezer, it’s mostly an inconvenience.
His was installed for $6,000.00? Did that include the generator?
I would very much like to know how it is vented. I have a portable that I need to get ready for Winter.
This is true. 
It needs to be outside when running. Not in the garage, not in the basement, but outside. Unless you have some sort of fool-proof venting system.
Two people died last year in my county because they thought it was OK to run a generator in a non-lived in, but enclosed space.
Yes – my move in with my father was contingent on his putting in a stand-by generator because the complex is at the end of the line and it can take quite a while to get the power back on. Luckily he hadn’t bought a house in decades so the tax credit offset the generator; it was in the $8K range.
If I were buying in this area, it would be a big plus for me.
We’ve lived here 10 years, and in that time, we’ve had a few very short power outages, and one that lasted 48 hours. Luckily, we’d had warning before that storm, so we filled our bathtubs with water to flush the toilet, and we were able to get bagged ice, so we didn’t lose any food. Based on that, I’d say in this area, such a system wouldn’t be a selling feature.
We do have a small portable generator - we had it at the time of the storm, but we didn’t have a connection for it set up (we do now.) It’ll run the well pump, the fridge, lights, and the computer - what more would we need? 
During an ice storm that took out the power for two weeks, I ran the trailer out in the woods with a portable. It ran the electronics for the furnace, the well pump, satellite receiver, TV and some lights.
It has to have oil added periodically. I learned to awaken when the engine noise changed, and stumble out into the cold to add oil. 
Ask anyone who lived through the 1997 Quebec ice storm and they would be willing to pay full value. And we get short power failures maybe once a year, but they are generally over in a couple hours. Still, it is frightening when it happens in the winter and you have no heat.
For those of us who keep tropical fish, and even more for salt water tropical fish whose life depends not only on heaters, but other devices, it threatens the lives of animals we have taken responsibility for.
Which has little to do with the OP.
I also do not understand “added value” and someone telling one what funds have to be spent to sell a house. If it needs a new railing, deduct the cost from the price. If you spent $5,000 on a generator, the house should be worth $5,000 more.
But I am an engineer, not a real estate person, whose type I worth up there with car salesmen, metal building salesmen and attprneys.
portable generators were mentioned.
i did some checking during the past year or two. one manufacturer (of whole house and portables) stated that portables produced dirty power (THD, total harmonic distortion too high) for microprocessors (computers, AV equipment, HVAC, major appliances). saying you risk malfunction or damage. so maybe check the specs of the generator and the nature of your loads.
By the time it goes through a voltage regulator in the PC power supply, I don’t believe that it would matter.
I had no problem with an inexpensive generator for two weeks with a satellite receiver, TV and PCs.
The labor to put in a generator is a big part of the cost. Getting the transfer switch wired into my main panel took several hours. The electrician also ran wire in conduit down the wall and underground to the generator.
That work won’t need to be repeated anytime soon. My mom’s first generator bought in 1997 was replaced in 2008. It was a very early model Generac and had blown several circuit boards. Replacing the generator was much easier than the first install. The electrician didn’t change any wiring. Saved quite a bit of money.
So buying a home with an old generator is still a plus. Because it can be easily upgraded. Just like a central HVAC unit can be easily replaced when it wears out.
But I can see why it really doesn’t add much value to the purchase price of the home.
For the people who have these whole house generators, what sort of maintenance program do you have them on? I’m familiar with maintenance for generators for larger facilities where routine maintenance was performed weekly or monthly. Besides oil and coolant changes, battery maintenance seemed to be a common repair cost. How often are they inspected and maintained? How many hours per month do you run them?