12 best and 12 worst things to buy at Costco

Big box warehouse clubs like Costco can seem like a great option for couples and families searching for the most economical way to buy the things they need. You can buy nearly all of your essentials there, if you're willing to buy a large quantity. Oftentimes, it seems like absolutely everything at Costco is being sold for a great price, so it's easy to fill your cart quickly, but looks can be deceiving. Yes, there are absolutely some items that you should be buying at Costco, but there are also some items that you probably shouldn't, for one reason or another, particularly if you're trying to save some money. If you want to know how to make the most of your Costco membership (and how to stop wasting your money while you're there), you need to know about the things that you should buy at Costco and the things you should stay away from.

Best: Bacon

Most people are reluctant to stray from their favorite brand of bacon (it is a very important kitchen staple), but according to Consumer Reports, that's exactly what you should be doing. Consumer Reports found that Kirkland Signature regular sliced bacon is not only tasty and well-balanced, but also typically costs less than competitor brands at other stores. It depends on your location, but you'll save about $1.50 per pound on average buying Kirkland Signature bacon at Costco. Bacon freezes well, so if you eat it, there's no real reason for it not to regularly be included on your Costco shopping list.

Best: Maple syrup

Pure maple syrup is a staple if you want the real thing on your pancakes, waffles, or French toast. If it's a staple in your kitchen, you should definitely be buying it at Costco. According to The Krazy Coupon Lady, organic pure maple syrup is only 32-33 cents per ounce at Costco. At Walmart, a non-organic maple syrup costs about 56 cents per ounce, Amazon sells maple syrup for about 66 cents per ounce, and Trader Joe's offers it for about 67 cents. It's a no-brainer to buy it at Costco. It'll keep well in the refrigerator too.

Best: Frozen pizza

If you like to stock up on frozen pizzas and you're a Costco member, consider buying them at the warehouse store. According to Good Housekeeping, Costco has four-packs of frozen pizzas for a very low price, meaning it'll be far cheaper for you to keep pizza on-hand than dial up the local pizza place. Not only that, but if you're fully stocked, it won't be much more difficult to put one in the oven than it'd be to order one either.

Best: Kirkland batteries

You want to make sure any batteries you're buying are ones that'll work well and last for awhile, so you can get the most bang for your buck, right? Buying Kirkland batteries at Costco can help you do just that. According to Kiplinger, you'll pay far less per battery when you buy them in large packages at Costco.

Best: Nuts

Nuts are a great snack and, for the most part, very healthy. They can also, however, be very expensive. According to Refinery29, if you want to make the most of your budget, but still want to be able to buy high-quality nuts, you should buy them at Costco. This 30-pack only costs about $20, which is a terrific buy.

Best: Prescriptions

Prescriptions are an important part of taking care of yourself. According to Consumer Reports, you can get your prescriptions filled at Costco without being a member and, not only that, but they're typically offered at a discount. Sometimes the discounts are so good you don't even really need health insurance. If you're trying to save at the pharmacy, looking at your options at Costco could be one way to do so.

Best: Cooking spray

According to The Krazy Coupon Lady, one of the best buys at Costco is cooking spray. The canola cooking spray at Costco costs about 15 cents an ounce, while at Walmart it's about 27 cents per ounce and at Amazon, the PAM four-pack is about 46 cents an ounce. Costco is clearly your best bet if you're looking to save some money.

Best: Half-sheet cakes

If you've ever had a Costco cake, you know they're actually pretty good. As it turns out, they're not bad on your wallet either. According to Good Housekeeping, the half-sheet cakes at Costco are typically about $10 or less, which is approximately half of what the same size sheet cake would cost at another store.

Best: Gas

While not every single Costco location has a gas station, if the location you frequent does, you should consider buying your gas there. According to Kiplinger, the gas at Costco is often cheaper than competitors in the same area. That being said, at some times lines can get very, very long, which means saving a few cents a gallon might not always be worth it.

Best: Canned tuna

Canned tuna is very versatile, so for a lot of people who are trying to eat filling foods on a budget, canned tuna is a pantry essential. According to The Kitchn, 16 (7-ounce) cans of Kirkland Signature White Albacore Tuna can be yours for about $35. It'll help you fill your stomach without breaking the bank.

Best: Baby formula

Baby formula — like just about everything else needed to care for your babies — can be very expensive. According to HuffPost, if you're looking to save money on baby formula, you should be buying it at Costco. Kirkland Signature baby formula costs about 50 cents an ounce, which is a total bargain.

Best: Alcohol

If you belong to a Costco, you probably already know that you can buy beer, wine, and spirits at some locations for pretty good prices, but those savings might not be only available to those who have memberships. According to The Kitchn, in some states, because of the liquor laws, even non-members can buy alcohol at Costco locations that sell it.

Worst: Sunscreen

Though it might be tempting to pick up plenty of sunscreen at Costco before heading off on vacation or in preparation for long summer days, it's just not a good idea. Jackie Warrick, Chief Savings Officer and President at Coupon Cabin, told TODAY that if you clip coupons and time your purchases right, you'll save even more at other stores than you would at Costco. Not only that, but sunscreen loses its effectiveness the longer it sits around, meaning what you bought last summer probably won't work well next summer.

Worst: Condiments

Condiments aren't a good buy at stores like Costco and other warehouse clubs because you have to buy them in such large quantities. Warrick told TODAY that you probably won't be able to use those giant containers before they go bad, meaning you're really not saving much (if any) money. Instead, you're probably better off clipping coupons or picking up smaller containers when they're on sale.

Worst: Anything you haven't tried before

If you've never tried something before, you probably shouldn't start with a big, Costco-sized box. According to Cheat Sheet, it's a better idea to try it in a smaller size from another store first to see if you like it or not. Then, if you do, you'll be able to confidently buy the much larger amount the next time you're at Costco.

Worst: Coffee

We get it. You love coffee and you'll totally use up that giant pack. It still might not be a good idea. According to Eat This, Not That, because coffee can lose its flavor over time, it's not worth stocking up on the kind you love just to have it be lackluster by the time you actually get around to drinking a cup. If you're not buying it for a business, you probably won't be able to go through it quickly enough.

Worst: Diapers

Diapers are expensive, for sure, but there are many places to buy them (relatively) affordably. According to Cheapism, the reason it's not a good idea to buy diapers at Costco is because you have to buy them in such large quantities, which means that your little one might out-grow them before you're able to use them all up. Not great.

Worst: Clothes

According to Kiplinger, you shouldn't buy your clothes or shoes at Costco or any other warehouse clubs because they're made with inexpensive materials so the companies can afford to sell them at such a low price. It can be super tempting to pick up what appears to be high-quality designer items for a great deal, but it might not be the best way to spend your money in the long run.

Worst: Things you don't have room for

It might sound obvious, but you really shouldn't buy too many items at Costco that you can't store. According to Cheat Sheet, sometimes it's not actually a better idea to buy in bulk. If you have to get super creative with how you're storing the supplies in your house, it might make more sense to simply buy those items in a smaller size — at least for now.

Worst: Electronics

You might think buying electronics at Costco is a great idea, but you might be paying more for them than you realize. Howard Schaffer, the founder of Offers.com, told Kiplinger that you can often find better deals on electronics on bargain websites, plus stores (and websites) that sell electronics typically put those items on sale a couple of times a year. So if you keep an eye out, you might be able to get just what you're looking for, for less.

Worst: Detergent

Detergent sounds like it would be the perfect thing to buy at a warehouse club like Costco, right? However, it might not be the best idea. According to Cheapism, laundry detergent starts to lose its effectiveness after about six months. You almost certainly won't be able to use up a large container of laundry detergent if you're only doing laundry for one or two people. For a large family, it might make sense, but for a single person or couple, it might be better to buy detergent in smaller quantities somewhere else.

Worst: Whole grains

Whole grains are healthy, but you shouldn't buy them in bulk at Costco. According to Eat This, Not That, since whole grains contain oils, they can go rancid. More refined grains will be more shelf-stable, which means rancidity is not as much of a concern. Buying whole grains from bulk bins at the grocery store, where you have more control over how much or little you're buying, might be a better choice.

Worst: Conventional produce

Conventional produce (not organic) isn't the best thing to buy when you're at Costco. According to Rather Be Shopping, conventional produce is often very expensive at Costco, so your local grocery store might actually have a better price on the same kinds of fruits and vegetables. Additionally, buying at Costco means buying large amounts and produce can go bad if it's not eaten quickly.

Worst: Cereal

Costco sells cereal in giant boxes, which makes it seem as though it's a super-affordable option, but that's not necessarily the case. According to Rather Be Shopping, if you break down the price of cereal per serving, you'll probably be able to find the same cereals at your local discount grocery stores for less. Not only that, but grocery stores often offer sales, which can make your bargain-hunting even more effective.