Enter the now very affordable solar attic fans. I picked up a 10W roof mounted one, installed it a few feet away from the Ac powered one but discovered that the one panel did not have the oomph to get the 24V fan going without full sunshine. (Motors need a lot of startup current to overcome starting inertia resistance) So I picked up another 10W panel and wired the two panels in parallel.
The new panel came with a mounting bracket that I modified with a few holes to sister next to the factory panel. I used a nonmetallic box to do the wire terminations. Make sure you tape up your wire nuts well or use a secure wire connection device. Now the fan will work in a variety of conditions so long as there is some light.
I kept the AC fan as some hot days or non-sunny days the solar fan will likely not be able to keep up with the heat load. Additionally, I had a very small leak due to a shingle issue - so the new solar fan hole killed two birds with one stone. Make sure to remove all the nails above and around the hole where the solar fan flange must lie. You have to be very gentle with the shingles especially if they are a bit older so they don’t crack. I used a small shingle removing tool to pry them up(to gain access to the roofing nails). Make sure to have a tube of waterproofing or roofing sealant with you while you are on the roof to fix any issues.
Make sure you get the temp cutoff switch if you live in colder climates and the fire safety switch to protect fire fighters and your house in the case of a fire. (these get mounted in your attic and after the quick disconnect to the motor. I used butt splice connectors for this task) I figure the solar fan will pay for itself in 5-6 years or so, but it is really nice to not have to listen to the noisy AC fan on except for the hottest part of the day. The solar one is pretty much silent from inside the house.