The Capitals say there is happy, and then there is “Nate Schmidt Happy.” (Matt McClain/The Washington Post)

Here is the first thing his Washington Capitals teammates mention about defenseman Nate Schmidt: The dude loves his Vitamin D.

“Sometimes we call him the Solar Panel because when it’s sunny out, he’s just so fired up, and that’s what’s funny,” defenseman Karl Alzner said. “See the lights, soak it in, and then he just. . . . Voom. He starts going.”

Once Schmidt heads outdoors, good luck keeping pace. Best grab onto whatever you can, such as facts from the book he read last summer about Thomas Jefferson, his favorite president. Or everything he learned at the University of Minnesota, where an IT class finished his degree in business and marketing. Or recommendations of jazz music, his recent preference for drives home from the airport after road games.

Poll anyone inside the Capitals locker room — or any NHL clubhouse, for that matter. They all take joy in their work, because their work is to play hockey. But between back-to-back games, late nights and aching muscles, tough days are only natural.

Schmidt experiences no bad days. He lives in a world of boundless enthusiasm. If he seems even the slightest bit sapped of energy, fellow defenseman Brooks Orpik will needle him by saying, “Wow. You’re not the same today.”

He likes swing dancing and vintage cars and laughing so hard his whole body shakes. He is the 24-year-old son of two convenience store owners with the consistent positive disposition even after the toughest workouts..

There’s happy. And then there’s “Nate Schmidt Happy.”

“It’s easy when you’re around this group of guys, when they let me be me,” he said. “I don’t have to hide any of the goofiness at all.”

Hockey love at first sight

In the family basement, empty except for the miniature nets, Schmidt shouts up the staircase, begging his older siblings to come back for one more game of shinny hockey.

“Get back down here,” he wails, already smitten before his second birthday. “I want to play again.”

With only four years separating her three children — Mike, Emily and Nate — JoAnn Schmidt needed an after-school activity everyone could attend. She enrolled Mike in a skating program at the local rink, where the beginners started with walkers so they wouldn’t slip. When Nate was old enough to join, he ditched the walker in two days. Pretty soon, he was rushing through homework after school, lacing his own skates and yelling it was time to go.

Though he also played football and baseball, Schmidt increasingly devoted himself to hockey. He strung up nets inside the garage for target practice and tore around the Minnesota cul-de-sac in roller blades, even if they were his brother’s, two sizes too big.

“He’s just always been like that,” JoAnn Schmidt said.

It was an ethic Nate later carried into his first job, a decade before he signed a seven-figure extension with the Capitals this summer and accepted the expectation of becoming a full-time starter for his third NHL season. Back then, his parents’ business had expanded from one Schmidty’s Gas and Convenience into a multi-town chain of family-run stores. The nearby Minnesota lakes always boosted business in the summer, so it helped that JoAnn and Tom Schmidt had free labor. And since he was the youngest, Nate got last pick of the tasks.

“Give him a job and he got it done,” Tom Schmidt said.

Nate cleaned bugs from the canopy or painted the gas islands, smiling and chatting with customers. He made regular rounds between stores, cruising in the 2001 Pontiac Grand Prix or the 1994 Chevy truck, fixing whatever needed fixing. Before long, when managers knew Nate was coming, they would stick his favorite pizza inside the oven.

“Double pepperoni, double cheese, double sausage,” he said. “You couldn’t even see the pizza. I ate it like a pie. It was awesome. That was pre-diet days. The good ol’ days.”

‘He beats to his own drum’

Almost a century ago, the Wabasha Street Caves of St. Paul served as a sandstone-enclosed speakeasy for gangsters during prohibition and the Great Depression, but on this mid-summer night its doors opened for swing dancing. Schmidt arrived with a date and was feeling pretty confident. After all, he was fleet-footed by nature and tried salsa in high school. Prepare to be impressed.

“I mean, they’ve had to replace flooring in some of the places I’ve been,” Schmidt said. “I think I have the X-factor.”

Then he walked inside, glanced onto the floor and realized he knew nothing about swing dancing. His date asked if he was ready. He asked for 15 minutes to watch, then took 30. But by the end, after stepping on a few toes, after sweating through his original shirt and the extras he brought too, Schmidt was hooked. He went home and watched YouTube videos to prepare, then returned to the Caves the next week.

“He beats to his own drum,” his agent, Matt Keator, said. “He does his own thing. He’s not self-conscious about going swing-dancing. He’ll do that as well. He’s got a great spirit to him.”

Here was Schmidt at his most competitive and creative, working his hardest to prove he belonged, using swing dancing as a supplement to his offseason training — pizza-free diet and all. That same trait established a dynasty at the annual family beanbag tournament, where Schmidt has won the championship belt six years running, and helped him grow from an undrafted freshman at Minnesota into a two-time all-American who, six months after signing his entry-level contract, debuted for the Washington Capitals.

During his first preseason appearance in 2013, a mid-September matchup Winnipeg in Belleville, Ontario, Schmidt sped down the ice, trying to catch the puck, and surprised Jets star Evander Kane by passing him before the goal line. To the best of Nate’s recollection, Kane asked something like, “Who the hell are you?”

Nate replied something like, “Maybe next time.”

The one-way, two-year extension he signed in mid-June required some “back and forth,” according to Keator, but the security showed faith in Schmidt’s potential, that he could handle the full-time starting assignment and surpass the 39 games he logged last season. When Keator called Schmidt to tell him of the team’s latest offer, Schmidt was busy coaching a select hockey camp in Minnesota. After “like seven” missed calls, he answered during an intermission.

“He was like, ‘Hey, we’re not going to pass it up,’ and I was like, ‘Great, let’s do it,’ ” Schmidt said. Only then did he ask how much money it was worth — $1.625 million.

When he arrived as a rookie, Schmidt said, his true personality only leaked out to several close Capitals teammates; he hoped not “to be weird, high-energy new guy.” Last season, as he bounced from stable starter to healthy scratch to injured minor-leaguer, the unfortunate result of a fractured collarbone suffered during a reassignment stint in Hershey, Schmidt brought the whole locker room into his orbit.

They learned that he called his father, “Soup,” because a buddy once quipped that Tom’s black hockey jacket made him look like a soup can, and that he once nicknamed a former teammate “DOAB.” (Schmidt invented the acronym, which stands for “Definition Of Anti-Beauty.”) With teammate Matt Niskanen he shared his passion for vintage cars, and the list he and Soup created of dream models to buy. On team bus rides, Schmidt began sitting with goaltender Braden Holtby, by nature a quiet teammate and therefore the perfect audience for soliloquies about finance, history or wherever else the mind sprinted to next.

“He’s got that energy to learn,” Holtby said. “He can’t sit still. Usually on the road, we get off a plane and he wants to go for a walk. He wants to see the city. Most guys want to go sleep. He drags me out of the hotel room, gets me out there, see different cities.”

For example?

“The best was Phoenix, when we had a couple days there. He was on cloud nine the whole trip.”