Possible Clues:

• Proficient; handy
• 'House full': getting out of it is beneficial
• Productive
• Consume energy, wasting resource ultimately that's valuable
• Having practical value
• Invaluable American fuel English brought to the front
• Advantageous to be young with a lisp ...
• Handy; proficient
• Handy; very able
• Handy American juice promoting energy