Several years ago, we had the same experience (power outage -- spoiled food). Since then, I've kept a few plastic jugs of salt-water ice in the freezer. When the power goes out for a few hours (a fairly frequent event, thanks to squirrels in summer, and ice in winter); the salt-water ice melts first, and saves the food from thawing even a bit. This simple expedient works for at least half a day.
If you try this, it's important to use salt water, not fresh. That's because salt water melts (goes through phase change) at a much lower temperature than fresh water. Because of the "latent heat of melting (or freezing)" the sacrificial salty ice can save a lot of expensive groceries.
I hadn’t thought of that. I see where the frozen saltwater will absorb heat, then go through a phase transformation and maintaining the same temperature until the transformation is complete and its transition temp will be lower than potable water.