U.S. shoppers have been waiting for the best possible deals and discounts as rising interest rates and food prices have led them to delay purchases of big-ticket items in recent months.
Online sales for appliances jumped 37% compared to average daily sales in June, while sales of toys rose 27%.
Data firm Numerator said the average Prime Day spend per order rose to $56.64 from $53.14 a year ago.
To add more customers, Amazon has partnered with travel booking site Priceline to offer discounts as U.S. consumers prioritize experiences over non-essential spending.
In the weeks leading to Prime Day, members of the loyalty program were given access to "invite-only deals" where shoppers could request invites to specific products that they were looking to purchase on deals.
Rival retailers, including Walmart (WMT.N), Target (TGT.N) and Best Buy (BBY.N), are also offering large discounts during the Prime Day week.
"Given the momentum we are seeing from day one, we expect day two to be pretty much at this level and that should allow us to see between $12 billion and $13 billion for the two-day event," said Vivek Pandya, lead analyst, Adobe Digital Insights.
Shoppers can find the biggest discount of 16% on electronics on Wednesday. Apparel is discounted at 13%, while toys would be 15% cheaper on Amazon.
Adobe's Pandey said the event is a chance to stock up on back to-school items, especially apparel and electronics, whose sales were up 26% and 12%, respectively, compared to average daily sales in June.
Data from Deloitte showed 69% of shoppers planned to rely on Prime Day sale for back-to-school purchases. But that spending is expected to decline for the first time in nine years as sticky inflation hurts non-essential purchases, it said.
Adobe's data relies on direct consumer transactions based on more than 1 trillion visits to U.S. retail websites.
Meanwhile, nearly 900 Amazon workers at a warehouse in Coventry, in Britain are striking over a pay dispute for three days from July 11-13, coinciding with the Prime Day sales event.
Amazon said the site does not directly serve customer orders and there will be no disruption to customers.
