I don't know about annually, but I had a pool just slightly larger (Lshaped) than that 6 years ago and heated it up in December for a birthday party. I distinctly remember my gas bill being $740 extra that month. We kept it at 75 for two weeks. I never heated it again. Running the attached hot tub 5-6 days/month using the same heater cost maybe $100 extra/month. Same latitude as you. This was a 'modern' Blue Haven built pool that was promised to be reeeeel efficient.

In VA we have a 40+ year old gunnite pool that is heated by a solar panel bank with a large recirculation tank in the well house, but it covers an entire section of roof--maybe 30x20 but was apparently very expensive as I found out when hurricane Isabelle sent a gum tree branch through two of the panels.