The most common and most likely answer to this crossword clue is the 8 letter word GIGAWATT
I've seen this crossword clue in The Times
G
I
G
A
W
A
T
T
Buddy explains!

The straight part
We know that "Much power" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case much power = gigawatt.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does GIGAWATT mean?
GIGAWATT noun- One thousand million (109) watts, abbreviated as GW.