Howdy,
I've got a pentair system on my 8500 gallon fiberglass pool. I was initially thinking I would want a heater/chiller combo, but the hottest my pool has gotten all summer is 90F. It's light blue, almost white so I guess that's why it hasn't gotten hotter.
The pool company is recommending a pool heat pump or natural gas heater. Gas access is not a problem due to location and the house is already plumbed for it. The unit would be about ten feet from where the gas enters my home.
It's not by a window or door so I don't think I'll have any coding issues.
I was thinking that I would be warming the pool to 82-85 in the fall and spring on the weekends and not even use it in the bad months like January and February. I live in corpus if that helps.
Which option is the better choice for something like this. My pool hardly got under 70 even in February this year if that helps.

Looking for info at ease of heating pool and cost of running.

Thanks again.

So the issue with a heat pump is below 50 degrees they cannot efficiently pull heat from the ambient air. Additionally, it's like adding an additional A/C compressor to your home, so if you know your current condenser's kWh consumption then you could figure roughly how much it'll cost to run.

If you're not worried about keeping the pool cool but want to heat the pool in the dead of winter, go gas.

The gas heater will use a lot of gas to heat a pool and you'll have to keep running it to stay at a certain temperature.

This article is specific to the Tampa, FL area but gives a good idea of the trade offs

https://www.hawkinsserviceco.com/blog/whats-the-cost-to-run-a-pool-heater/#:~:text=Natural%20Gas%20Pool%20Heaters,that's%204%20therms%20per%20hour.

ETA

The easiest/cheapest route may be to start with a solar blanket to help absorb & trap heat in the early months before dropping the coin on either type of heater.