What is the most commonly used alternative energy product?

depends on where you live. in illinois,we have eleven nuclear reactors. there are a large number of large windmills for generating electricity. i think the nuclear power plants are a better long term investment. the wind does stop blowing on occasion. october 11th there was no wind in the dekalb area

Hydro power could be used only b Governments. Normally Solar energy, Bio gas energy, Windmills energy are used in limited scale

I would think Solar energy is the most common, if not then as technology improves and the price of solar panels reduces then it defiantly will become the main source of energy in the future.

Since your energy meter for your electric service makes no distinction, there is no way for you to quantify useful amounts, but as for products- consider the lowly desk calculator- millions of them are around and as ubiquitous as the old pay phones used to be.

The most common form of renewable energy is actually hydro power. Out of alternative energy choices, I think that solar is most common.

wind is solar powered

well i would have to think the solar energy but when going by the colombus river area that place has over 100 fans going for wind energy

solar energy

Biomass. Imagine all the people that burn wood...