For most batches, the freezer dryer uses as much energy in 24 hours as the entire rest of my home. Freeze drying is the most energy intensive method of food preservation, but its also the most beneficial. Unlike other methods such as canning(30%?) or dehydrating (50%-70%?), freeze drying retains something like 97% of the food's nutritional value. Storage times are also ridiculously long. Canning is about 2 to 3 years, dehydrated food can go 10 years if packed in oxygen free environment.. Freeze drying can go 25 years or more.
There are also a lot of foods that can be freeze dried, but not canned or dehydrated, so a lot more options for food storage.
And when it comes to meats, its hard to tell the difference between freeze dried and frozen. Nothing compares to fresh obviously, but most meats re-hydrate extremely well. We have freeze dried about 200-250 cans of tuna fish and you can't tell the difference between what just came out of the can and what was re-hydrated.
Of my favorites are Thanksgiving dinners.. When the turkeys go on sale every November, my wife will get 6 to 8 of them each year. She'll cram in the stuffing and cook a turkey every weekend.. We'll make one dinner out of it, then freeze dry everything that's left and repeat the process every weekend until they're all gone.
We do somewhat of the same thing every Easter with the hams.
It is energy intensive, and the machines are kind of expensive as they're up in the $2500 to $3500 range. Being on solar, I don't care about the energy as we produce way WAY more power than we use.
Next to having a weapon, the freeze dryer is a huge prepper item. One #10 can of Mountain House ground beef is like $90.. that's one batch in the freeze dryer + $25 to $35 worth of beef. Plus, I can freeze dry it raw or precooked.