Tim Easterby's flying machine won for the third time on the Knavesmire this season with a devastating performance over five furlongs, as she defeated strongly-fancied rivals from America and France.
US raider Golden Pal was quickly away for Frankie Dettori from stall one on the far side - but Winter Power was also up with the speed from her draw in six.
Golden Pal's run petered out disappointingly before the final furlong, but Winter Power (9/1) sustained her gallop for Silvestre de Sousa all the way to the line to win by a length and a quarter.
Emaraaty Anna (40/1) was second, with Dragon Symbol (4/1) half a length away in third.
Suesa, the 9/4 favourite for French trainer Francois Rohaut, was fourth, but Wesley Ward's Golden Pal was only seventh.
Great Habton-based Easterby - whose family is synonymous with York - said: "As long as we went straight and didn't mess about, she had a chance.
"We didn't go anywhere else, we resisted going anywhere but she's just brilliant, it doesn't matter where she goes.
"It's taken a long time to get to a race like this, you have to give them time and you have to be patient.
"With her, she's just a superstar, you don't train her and you don't train her hard.
"When she came up there she was just on her toes a little bit and she needs to settle and not do too much.
"I'm so thrilled for the owners (King Power Racing), the investment that goes into these horses is incredible."
He added: "We'll just enjoy today, I've never been to Del Mar (Breeders' Cup), we'll keep her for this next year.
"You've got to get them home and see, even though she's won easily, she's had a hard race."
De Sousa said: "She's unbelievably fast, when she hits the gates right she's really good.
"She did that here first time this year and I thought I hadn't sat on anything as fast as her.
"She was very good, on a track like this she just hit her stride straight away.
"I'm just pleased for the King Power team, they have put so much effort into these races.
"They have a great horse for the future, this is her first Group One so hopefully we can keep it going.
"There were no orders, I spoke to the team who said to keep it simple, which is how I like to ride.
"I was confident, I was riding for the best place possible and trying to win the race.
"She's in great form and she was the best on the day.
"I could see Frankie, he was in front for the first furlong where she was going too well."