Look into "natural" or "eco" or "green"(not the color) pools.
It basically uses a pond as the filtration/cleaning method including pond plants and stones to do the clearing instead of nasty chemicals and expensive equipment. All you would need is a pump...and as a bonus you get a nice, natural looking pool with waterfalls and plants, possibly even fish living in it if you want. I've built ponds for years and am certain when I decide to build a pool I'll be doing this.
Dunno....i've never seen an "underground" pool, mine is an in-ground pool, methinks that is what you meant. On mine, not including maintenance/replacements items, just chemicals and filter earth, i'm guessing about $500/yr.
FYI...you have to really want a pool to justify the expendeture, because come resale time you will NOT get much of your investment back in extra apprasal value, 50% if you are lucky.
As RNDDUDE advised, I also spend about $500 per year for my pool, provided I don't have a major failure like my pool filter exploding 2 years ago, which set me back $1,000. I also just replaced the pump for $350, and had to re-plaster and re-tile 3 years ago, at a cost of $5,000, but the biggest cost is the inflation of your property taxes, which never goes away.
Considering the pool is only 9 years old, that is a big chunk of change for a hole in the ground. If I didn't like the sound of the waterfall, or my dip about 5 times a year, I'd get a backhoe and fill it with dirt!
Havasu, your experiences and mine are very similar. I didn't want to add the non-recurring costs for fear of scaring loop off. In the past two years I have had to do the following to my 35 year old pool:
New pump, new earth filter, new heater, complete re-tiling and re-plastering. With a new pool, these would not be issues. That being said, I bought this house with the pool already in, but it wasn't a factor in the purchase. In reality, I spend FAR more time doing routine maintenance (I do it myself) than I ever spend in the water. My adult kids love it when they visit with the grandkids though....
My best investment with the pool purchase was the auto pool vacuum with its own dedicated line, the auto water filler, the auto overflow drain, and the auto chlorinator. I skim once a day, brush once a week, and add acid about every 4th day. My son pays $75 per month at his house for complete maintainance, but I'm just way too cheap for that.
Haven't availed that service yet but the company that provides me pool cleaning service in Newport Beach offers that service, too. You might want to contact them. They're professional and won't slash your pockets. That I can guarantee.
Do not waste money on a salt system. I've been down that road, now I'm back to the "auto chlorinator", which is nothing more than a plastic canister, inline with the pool pump flow. 2 or 3 tables a week go into it.
Regarding cost, can't be more than $300/yr for me. Occasional pool cleaner part, occasional acid, and those chlorine tablets.
What size of pool are you planning will determine your cost. You need an appropriate size pump/filter to meet the needs of your pool and the bigger it is the more it will cost. I'm sure my 1.5 hp pump hits up my electric bill for $30/month and then for me chlorine tablets and algaecide. Easily $500/year.
I, like others that have responded, don't get in it much, and you better have some payoff for it if your the one paying for or doing all the maintenance. I bought my house 5 years ago and had to put in a new pump and filter to the cost of about $1000. The screen around the pool needs to be redone and the liner has had several leaks which have resulted in the most time I've spent in it the past 3 years, when I fix them. btw mine's an in-ground vinyl pool @25k gallons. When it's time to reline the pool, it's either getting the deck tore up and dumped inside or all the plumbing redone and making it with a concrete liner.