Before, you could count on burning a few calories walking from your car to the grocery store, or roaming the aisles to load up on what you needed.

But that notion has gone out the car window, as major supermarket chains and big-box retailers, such as Walmart, are investing heavily in online grocery and curbside pickup.

And with good reason.

Online-retail analysts estimate that U.S. consumers spent about $24 billion buying groceries online last year, or about 4 percent of their total grocery spending of $591.6 billion on grocery shopping, according to the U.S. Commerce Department.

But an estimate from Brick Meets Click, a grocery research and consultancy, forecasts that online grocery spending in the United States will reach as much as 17 percent in most markets by 2023, about four times last year's amount.

Peapod, the nation's oldest online grocer, has partnered with Giant since 2011 in the Pennsylvania market.

Peapod.com is the website on which Giant customers shop online for groceries, and request either next day home delivery, or curbside pickup at select Giant locations.

Giant stores in Fairless Hills and Morrisville, both in Bucks County, were added last week to the 19 in the region that already offered curbside pickup, including those in Springfield (Delaware County) and Wynnewood.

Marlene Bower, 35, of Langhorne, uses Peapod.com every other week. Because her order is consistent and she is a Giant regular, she is able to use the previous list.

"I love it," said Bower, a local store manager, as her Ford Edge SUV was being loaded at the Willow Grove Super Giant by store employee Graham Simon, 21, of Willow Grove. "Especially when it's cold - I don't have to get out of my car.

"I just pull up and they have my order ready," she said. "They've done the shopping for me."

All the bags were placed in the SUV, except for the one with a dozen eggs. Simon walked over to Bower on the driver's side window, asked her to quickly inspect the eggs, and handed them to her to place in the front seat.

As with all Peapod by Giant orders, Bower's was prepared the night before by "Peapod shoppers," such as Lea Bell, 25, of West Oak Lane, in the back area of the Willow Grove Super Giant. It has opened a "Peapod ware room," a mini-version of the main shopping floor that has most of the major brands in the aisles. There's even a tiny section for produce.

Bell wore a wrist mount on her right arm that showed an online order, and what items to pick out. She placed the items in a green plastic tote.

Once all her totes were filled, they were loaded onto trucks for a 5 a.m delivery the next morning. The trucks were headed to either private residences, or curbside pick-up at select Giant stores.

Giant first launched the pickup service at the company's Willow Grove and North Wales stores in November 2013.

"The service has been embraced by the folks in the Philly metro area," said Peg Merzbacher, vice president of regional marketing for Peapod.com, who is based in Quincy, Mass. "We have had double-digit sales growth each year since it started in 2011."

E-grocery sales are expected to rise 21.1 percent a year through 2018, concludes research firm BI Intelligence, compared with 3.1 percent for physical supermarkets.

"The future is here," said Paul Gobiel, supervisor of the Peapod online grocery service at Giant. "More and more, people are time-starved. . . . Customers like the convenience."

Giant shoppers can use the Peapod app on their smartphone and enter their zip code or Giant bonus card number. They select a payment method, either debit, credit, or their Giant bonus card after filling an online cart, and choose between next day delivery pickup, or a two-hour delivery window.

The minimum order is $60, with $2.95 added for curbside pickup. Delivery to homes is on a sliding scale. If the grocery order is more than $100, the fee is $7.95. Coupons are accepted and doubled, based on the same guidelines as your local Giant.

"The easiest way for grocers to get into e-commerce is by offering a click-and-collect model," said Matthew Moreau at MyWebGrocer, an online software provider for the grocery industry. "They already have the infrastructure necessary: a supply chain, labor, brand recognition, and close proximity to shoppers. When given a choice of having their groceries delivered or picking them up, 70 percent of the time customers will opt to pick up their groceries."

Wegmans is testing curbside pickup at a store in Pittsford, N.Y., and one in Bridgewater, N.J. A customer can order online, using the Wegmans app for curbside pickup. There is no roll-out schedule at this time, said Wegmans spokeswoman Jo Natale.

Meanwhile, ShopRite offers a ShopRite From Home Service and the ShopRite Mobile app, which allow customers to shop online and pick up groceries at select ShopRite/Fresh Grocer stores, or have the groceries delivered to their doorstep.

"It's a cool idea," said John Feehan, 21, a restaurant cook, as he strolled to his car carrying a bag of snacks past the huge, "Coming soon, Giant Pick-up" sign in front of the Fairless Hills store a few days before the curb-side launch.

215-854-4184 @SuzParmley