KNOXVILLE, Tenn — The biggest shopping day of the summer is here. 

Amazon turned its annual Prime Day sale into a 48-hour affair starting at midnight July 15.

"Who doesn't love a big sale? I mean, It's cheap. It's Black Friday in July," tech expert Luke Wood said. Wood works as Allevia Technology's chief people person.

This year, the online retail giant is promising deals on more than one million items with bargains popping up as often as every five minutes. 

Whole Foods will also have discounts in-store including a 10 percent discount on hundreds of products.

"The places that you can really rack up some cool savings are electronics, gaming, health and beauty," Wood explained. "Chargers for your cars, chargers for your house, chargers for your desk, charge cables, anything like that that has high margins goes on sale usually at pretty deep discounts."

But you won't be able to snag any of the deals without a Prime subscription.

The membership costs $119 per year or $12.99 per month.

You can cancel at any time if you choose the monthly option.

A Prime membership also comes with other perks like free one-day shipping and access to Amazon's streaming service.

Amazon says Prime Day is its single largest day to acquire new members.

Experts say deciding whether the sale is worth the subscription price depends a lot on what you want to buy. 

The online retailer has already dropped some deals.

For a limited time, Prime members can get the Fire TV Recast for $130.

Prime members can also score four months of Amazon Music Unlimited for just $0.99.

But that promotion is only for new Music Unlimited subscribers.

Starting now, you can also save $30 on the Echo Dot (3rd Gen).

Wood said consumers can expect to see the biggest savings on electronics, including a couple hundred dollars off items like televisions.

Prime Day's electronics deals are so good they could even beat Black Friday discounts. 

But when it comes to things like household items, clothing and outerwear, you could find them for less elsewhere.

"Look for that item, and say is this really as good of a deal as they're telling me it is?" Wood advised.

A sales war is budding as well, with other retailers launching massive sales to compete on the same days.

Target's competing Deal Days event promises the cheapest prices on home decor, apparel and toys.

Ebay is offering extra deals if Amazon's website crashes after last year's Prime Day outage.

Wood's final piece of advice? Make sure to compare prices before you check out.

"Amazon itself has a Chrome plug-in that when you pull up an item on Target's website, if they have a matching item, it will pull up a banner that shows you that item and how much it costs, so you can just use that kind of stuff to your benefit."