Both Sam's Club and Costco Wholesale stores say they offer up to 30% discounts on brand items.
So why don't you always see those savings? Consumer Reports says, for one, people buy way more than they plan to get.
One shopper told us, "Well, if I see something additional that I like, I buy it."
Another said, "I just load up because it's a bargain."
A third explained, "When I come, I spend a lot of money."
Consumer Reports' Tod Marks says maximizing the savings takes some discipline.
Tod says, "Before heading out to a warehouse club, make a list and then stick to it."
That means resist the urge to browse. You can get great deals on electronics and jewelry, but is that what you headed in to buy?
If you're short on willpower, Consumer Reports says try shopping at the club websites.
Tod explains, "Sam's Club has this great service called "Click 'n' Pull." If you place your order online before five o'clock, you can pick it up the next day."
And both sites offer "online-only" specials.
Back in the stores, check out unit prices. That way you're sure you're paying less than you would at the grocery store. Sometimes you're not.
And if the big packages are too big, good news. The warehouse clubs are offering some smaller sizes in a lot of staples.
Tod says, "But some items still come in bulk. So if your favorite products are only available in bulk, consider splitting it with a friend."
And another money-saving move - try the cheaper warehouse club brands - Kirkland Signature at Costco and Members Mark at Sam's. A plus, many products have rated highly in Consumer Reports' tests.
Membership at Costco starts at $50 a year, Sam's Club at $35. If you're not sure it's worth it, Sam's Club offers a one-day pass that allows you to buy anything you want with a 10% surcharge.