Ours is 30,000 gallons and costs about $1000 per year in pool chemicals/nets/poles/replacement parts, etc. I can't break down the electricity but I don't notice that big of a difference between our house and my father's which is basically the square footage size minus the pool. The pool pump runs one hour for every 10 degrees of temperature. On an 80 degree day the pump runs 8 hours while on a 100 degree day it is more like 10 hours. We do not heat ours nor do we have to winterize it. Those would both add significant cost. We have lights but we don't use them that often. It's just lights, though, so I can't imagine that would make a big difference. We did install a Polaris and with a timer that ran us about $1000. Well worth the money since it helps with stirring up and picking up debris.
We do our own pool maintenance and it is not that hard once you get it down. We got a local pool guy out for a couple hours of time for $200 (pool school as he called it). Checking the chemical levels is not that hard and needs to be done daily. With a large volume of water the chemical balances don't swing that drastically so long as you do basic maintenance (keep the chlorine in it, scrub it, clean skimmer baskets). You can take the water sample to your pool store and they can help you. The scrubbing sucks the most but it has to be done every day in the open season. The skimmer baskets also have to be cleaned daily. Sometimes more often every day especially in the spring when the neighbor's trees are blowing debris in the pool. We cajole ourselves by saying it's good exercise.
The older lady we bought our house from had a pool service. I believe she said the service was $50 to $100 per two weeks but she never lifted a finger. The service came out to clean the skimmers and to add their chemicals.
I would suggest a fence over a pool cover. A pool cover of the caliber you are describing (safe enough for a child to walk over but not sink into the pool) will be at least $1500 dollars and will be custom fit to your pool. Removing the pool cover is a pain and is not a one man (or woman) job. You also have to factor in where you will store the cover when it is not in use. We only cover our pool with a mesh leaf net in the fall/winter. It stays covered from about October/November to March/April. We don't have to do any maintenance so having the pool, deck and skimmers covered is no big deal. Without the leaf net we would have to constantly cleaning out the fall leaves and then the spring leaves. Big mess. When we store our leaf net, we have to take it off the pool, allow it to dry thoroughly and then drag it into the cul de sac to fold down for storage. It's mesh so that's not bad. A solid cover would be a challenge.
Instead of a pool cover I would recommend a fence. We have a fence and it was about $1200 installed. The fence is rated for 200-300 pounds per section. Big Uncle Fred can topple into it and it still won't collapse. Our fence is also removable which is convenient when we have adult only parties and don't want to look at the fence.
The pool pump lasts about 5 to 7 years so you can see what those run you. About every 15 years you'll have to replaster. We did that two years ago and it was a big job both in terms of cost and work. We accepted the cost when we bought our home. In Houston the summers are just too long without a pool. Good luck in your decision making.
Oh, one other thing about the landscaping. Ours doesn't have any because it takes up almost the entire backyard. Our little patch of grass is a pain when we mow. It takes an artful hand to keep the mowed grass out of the pool when mowing. However, our neighbors planted a pecan near their pool. Why? The constant debris and the roots growing into the pool is just foolish. Keep the landscaping as clean as possible and as damage free as possible. Think minimal. You don't want roots growing into your pool, skimmers or decks. All of which would equal damage and cost. Plus you don't want a constant mess in your pool. We have several crepe myrtles thanks to our neighbors. The continual flowers are a mess. Think palm trees, pond grasses, etc. If it winds up in the pool, it has to get cleaned out by either you or your pump.
One other thought ours looked like a swamp when we moved in since it hadn't been maintained in a while. We did have a pool guy come out to give us the extra muscle to get it clean. He checked the levels and added the necessary chemicals to get it right. It was a fairly painless process and it only looked bad for a week.
Sorry, one more thought. Get a pool inspection separate from your other inspections. You need a qualified service to verify you don't have leaks in the pool lines and/or skimmers. Also you want to have a good look at the condition of the deck, pump equipment and pool. We negotiated on the price of our home because the pool had some issues (leaks from the skimmers were causing the deck to cave in and a future replaster job within two to three years of purchase).