The Lightning tied it 1-1 at 10:00 of the third period when Kucherov shot over Holtby's left shoulder from the slot.
With the score still tied, Tampa Bay had a 5-on-3 power play for 1:26 beginning at 11:09 but did not score.
"We have a chance to go up [on the 5-on-3], and we don't do it," Lightning forward Brayden Point said. "They come back after that to score one, and we're chasing."
Holtby said of the 5-on-3 penalty kill, "We stuck to our process, and we trusted me to make those saves, took away lateral options. They're going to get looks. They're too skilled not to. It's just a matter of when they get them, don't get running around after [them], and we did a great job of that."
The Lightning were 0-for-7 on the power play. The Capitals were 0-for-3.
"We're a proud group and we're not happy about our performance on the power play tonight," Tampa Bay defenseman Victor Hedman said. "We take it upon us to go out there and get us goals and get us momentum, and we didn't do that today, and that's on us."
Washington took a 1-0 lead at 4:40 of the second period on a Gudas slap shot from the point that appeared to deflect in off Tampa Bay defenseman Mikhail Sergachev.