When energy flows from one trophic level to the next higher level what always happens?

When energy flows from one trophic level to the next trophic level most of the energy lost as heat in the process.

Explanation:

The food chain is transfer of energy in the form of food from one trophic level to next in an ecosystem.

Energy flows from at each trophic level when organism of higher level consumes organism of the lower level.

Energy flows at each trophic level by 10% Rule which states that only ten percent of the energy will be transferred on at each trophic because of the following reasons-

1. Energy is lost in the form of heat at each step

2. Only consumable energy by organisms is transferred at the trophic level.  

3. Energy is lost through different biological processes such as respiration.

it creates acid rain