There are many different types of powdered milk on the market. They have a full range of flavors, none of which in my mind taste exactly like fresh milk. The prices vary from around $20 for a number ten can down to $8.60 for a number ten can at the LDS (Mormon) canneries.
I have heard people say that the milk from the LDS cannery is not the best tasting. Since we use most of it for cooking and not drinking, I have not been too worried about the taste. However, last year we went for over a month living off our food store and about 2 weeks or so in, I asked my wife when we were going to start using powdered milk. Her answer, while laughing, was last week. I had been eating it on my cereal for a week and had not noticed.
There are several things you show watch for when buying powdered milk, and the most important is where does the milk come from? There have been numerous reports of exported dry milk from China being contaminated by melamine cyanurate, which is normally used as a fire retardant. Try to get milk that is from the U.S.
A second consideration, is it whey milk. This is a milk drink like Morning Moo. It is nutritious and good tasting, but only has a shelf life of about ½ that of powdered milk or about 10 years. I know families with kids who love it, but before buying, read over the list of ingredients to make sure it will be okay with your family.
One type of milk that is found on a more limited basis is dry milk that doesn’t contain hormones. Commercial dairies inject cows with bovine growth hormone so they mature more quickly and produce more milk. Stocking up on dry milk that does not come from cows given this hormone is a good idea.
Good nonfat powdered milk stored correctly at a temperature below 70° F, kept in the dark and dry should last 20 years according to studies performed by Brigham Young University.
If you choose to use the nonfat powdered milk form the LDS canneries, here is a link to their locations. You do not have to be a member to use the canneries in most areas, but you should call first to verify hours of operation, availability of whatever foods you want, and any other requirements.
How much powdered milk to store
Since you are going to be preparing all your food from scratch, you will need more milk than normal. I would recommend 100 lbs per person per year. For a family of 4 you would have 400 lbs for 1 year. This provides you with a good source of protein and calcium and gives you the ability to also make homemade yogurt and Preppers Cheese.
Now is a good time to increase your storage, food prices are going to increase in the near future.