Which method is best for temp/utilities cost prediction?

So i may have gone a bit overboard on this... but i think im onto something. I never took statistics or anything (yet) so i wanted to consult better minds than I. Ive been working on this for a while and im getting overwhelmed with it...

I downloaded the last 90 years worth of daily temp data from NOAA for my location to go along with my utility bill data that i update my workbook with regularly. My goal is to get a rough idea of daily temps throughout the year, then do the same with how many kWh/CCF use for cooling/heating my house when the temp is X. But idk which way is best. I have daily TAVG, TMAX, and TMIN data from 1931-2026 and about a years worth of daily power/gas costs. I used FORECAST.ETS to plot out the next 5yrs temps... But should I match TMAX with power bill cost and vice versa since i have electric cooling/gas heat? Or match both utilities to the TAVG?

Edit: maybe i used the wrong flair... not sure if this is a problem or a discussion lol feel free to correct me