Under strømbruddet var det stille i huset.

to be

Breakdown of Under strømbruddet var det stille i huset.

• huset: the house
• i: in
• det: it

Questions & Answers about Under strømbruddet var det stille i huset.

What does Under mean in this sentence? Is it the same as the English “under”?

Here Under is a temporal preposition meaning “during.” It does not mean “beneath” in this context. Norwegian often uses under for events that span a period of time. You could also say i løpet av strømbruddet, but under is more concise.

Why is strømbruddet in the definite form?

Strømbrudd (“power outage”) is a neuter noun. To refer to a specific outage, you make it definite by adding -et, yielding strømbruddet (“the power outage”). The indefinite form would be et strømbrudd (“a power outage”).

Why does the verb var come before det? Shouldn’t the subject come first?

Norwegian main clauses follow the “V2” (verb-second) rule. If you put an adverbial phrase (Under strømbruddet) in front, the finite verb (var) must come next, pushing the subject (det) to the third position. A neutral word order version is:
Det var stille i huset under strømbruddet.

Why is det used here as the subject? I thought “the house” was the subject.

This det is a dummy (expletive) subject, similar to English “it” in “It was quiet.” Grammatically, det doesn’t refer to the house; it just fills the subject slot so you can predicate “stille”.