You’d have to check with your HSA administrator, I’m afraid. A back-up battery or generator SHOULD be an approved expense, but I wouldn’t be surprised if you have to go back and forth with them about it.
That said, a backup is less critical with PD, since gravity drainage can be done. So, I have only heard of folks who do home HD getting them, not PD. It might be overkill. But, it would be a great idea to get those flashlights that plug in and power on automatically when the power shuts off, or at least keep a flashlight with fresh batteries near the cycler just in case.
If you do decide you must have a generator, Medicare covers them. Here is our article about emergency preparedness, which may be helpful. https://homedialysis.org/life-at-home/articles/disaster-planning-for-pd-and-home-hd.
If you are on Facebook, you also might want to join our group there. https://www.facebook.com/groups/HomeDialysisCentral/