2.5kWh seems like a lot to wash some dishes when some European models (which use cold fill) can go as low as 0.6 kWh.

The difference is mostly to use as little water as possible - just enough to wet the surface of the dishes not to soak them, and heat only the wash water not the 2 sets of rinse water or the prewash water.

There are some neat tricks to do this - for example there is no water level sensor - you aren't aiming to fill the bottom of the machine - instead you run the pump at full speed and keep adding water slowly till the pump electrically feels like it doesn't have many air bubbles in it.