However, the warmer the source of heat, the more energy efficient it will be.

He said the center could "create a more efficient and cost-effective source of energy, which will, in turn, contribute to our economic growth."

But greater stability and transparency makes them more efficient sources.

Since animals are higher on the trophic level, they are less efficient sources of food energy.

The iron oxide process requires an efficient source of heat.

The most efficient source of electric light is the low-pressure sodium lamp.

The working group aims to promote clean and efficient sources of energy such as bio-fuels.

The design is intended to evoke mid-19th-century historical poles, but with efficient modern sources and methods.

But turning an ordinary fireplace into an efficient source of heat takes some work.

Fish that occupy the higher trophic levels are less efficient sources of food energy.