This is the 7211th most frequent Korean word.
줄었다고
"줄었다고" means "said that [something] decreased" or "said that [something] reduced."
Here, '줄었다고' is used to indicate that a decrease has occurred, specifically referring to the temperature that has gone down.
온도가 줄었다고 느껴진다.
It feels like the temperature has decreased.
In this sentence, '줄었다고' conveys the information about an emotional state that has reduced, as understood through hearsay.
그의 기분은 줄었다고 들었다.
I've heard that his feelings have lessened.
'줄었다고' here introduces a reported fact regarding the reduction in electricity consumption.