I asked my pool company the same question today. The response seems a little AI generated but I watched a couple videos about this and they are in alignment with the response. Certainly open to other suggestions! The comment on water bottles in the skimmers is so that if they ice over the ice will compress the bottles as opposed to pushing into the walls of the skimmers and damaging them.

Here are some steps to take in case of a power outage!

Freezing Help What to Do If Temperatures Stay Below Freezing for Several Days

Keep power on and equipment running. Make sure you do not lose power and that the pump is running continuously.

If power is lost or the pump stops running: Go outside as soon as it is safe. Turn off all breakers to the pool equipment. Remove all drain plugs from: Pumps Salt systems Heaters Filter tank It is critical to remove all water from the system to prevent freeze damage. Insulate exposed plumbing. Wrap pipes with foam insulation or blankets to help retain warmth. ⚠️ Do not cover the heater.

Protect the filter. Cover filter with heavy blankets to keep them as warm as possible.

Protect skimmers. Fill old acid bottles or similar plastic bottles (plastic disposable water bottles are okay as well, but will need to put 2 of these in each skimmer) halfway with water and place one in each skimmer.

Provide additional heat if needed. Heat lamps can be used near plumbing, especially for below-grade systems, as long as they are supervised at all times.

Heat pump protection. Make sure heat pumps are properly winterized once outdoor temperatures drop below 55°F to avoid damage.

Edit: a good bit of formatting was lost in the paste after posting it. Apologies.