For some of your food shopping, warehouse stores offer low-cost alternatives to supermarkets. We surveyed Costco, Sam’s Club (which has only one Bay Area location, in Concord), and Smart & Final. These outlets carried few if any of the items in our market basket in the usual sizes, but when we looked for the same brands regardless of size, warehouse stores, which specialize in bulk sales, stocked a larger portion of our market basket items. Smart & Final had 77 percent, Sam’s Club had 45 percent, and Costco 39 percent.

The figure below indicates how much warehouse stores could save you. Since the warehouse stores stocked so few items in the sizes of our basic market basket, we looked for items of any size, so long as they were the same brands. We then used unit prices (for example, price per pound) to calculate the warehouse stores’ prices for amounts specified in the market basket. After this adjustment, we compared the prices of items at the warehouse stores with prices for the same brands at several other stores. Bear in mind that this is not an “apples-to-apples” comparison; the sizes of the items priced at the warehouse stores were usually larger than the sizes of the items priced at the other stores, so the warehouse stores enjoy an advantage in such a comparison.

The three warehouse clubs all offer significant savings for most shoppers. Costco and Sam’s Club, for example, each beat Safeway’s prices by a whopping 33 percent. And compared to Safeway, the savings were about 11 percent at Smart & Final. While we found Costco and Sam’s Club offered significant savings compared to even the lowest-priced local grocery store options, we found shopping at Smart & Final won’t net you savings compared to what you’d pay at Grocery Outlet, WinCo, Walmart, FoodMaxx, or Target.

In addition to having low prices, Costco received very high ratings from its customers for the quality of its meat.

While Costco and Sam’s Club offered significant savings compared to prices offered at grocery stores, these savings perhaps aren’t enough to justify paying their annual membership fees if you don’t use them often. (Smart & Final doesn’t charge an annual fee.) And if half of what you buy is wasted due to spoilage, you won’t save by buying in bulk.