If you could use any source of energy for heating your food, which one would you use and why ?

Explanation

I would use LPG (cooking gas) for heating food because :
(i) LPG has a high calorific value. It gives a lot a heat (per unit mass) on burning.
(ii) LPG burns with a smokeless flame and hence does not cause any air pollution.
(iii) LPG does not produce any poisonous gases on burning
(iv) LPG does not leave behind any ash after burning