Will the merger reduce Ethereum's energy consumption?

Yes. will be greatly reduced. This is one of the main results of The Merge and PoS.

After the merger, the energy consumption of Ethereum will be reduced by about 99.95% compared to the current level.

PoS secures the blockchain with capital, not energy. So the energy required to keep Ethereum running after the merger is comparable to basic computer usage: like what you're doing right now, such as reading this article, sending a tweet, downloading a movie to your hard drive, etc.

With PoS enabled, the energy cost of Ethereum is just running a node — about 2.6 MWh per year. That's about 1,300 times less than the entire U.S. gaming industry consumes.

Ethereum will actually be the greenest financial system in the world.