Less obvious are other hidden costs for light, heat and refrigeration. These costs rise when a store is open. This helps explain why Walmart lowered its earnings guidance for the year. Door-buster sales aren't just bought with markdowns, they're also bought with heat, refrigeration and payroll. Ultimately, it's way too early to predict how Walmart will fare this holiday season. So far, it looks like store sales will still increase slowly while earnings will dip. Walmart will continue to re-grow its market basket and top-line sales. It's a good investment really. The key may well lie in its online business. Walmart would certainly not be the first and only retailer to find most of its growth coming from digital channels. Still, it's good to see the company's trajectory start to change and it will be fun to watch this holiday season.