If we want to save energy, we need to choose more efficient light bulb since we use them quite much in our daily life. Their reflection to the electricity bills differs from each other. Why they are different? Which features lead us to this result? Which one is more sustainable? Do they have side effects on human health? Searching for the energy saving on bulbs, we look for a bulb if it converts how much its energy to give light, since light bulbs also convert some of their energy to heat. The part that is converted to heat energy is not an energy that we can use for illumination, so this part is not what we want. With this thought we are heading towards LED bulbs due to they give most of their energy for lightening. Although LED bulbs sold at higher prices than fluorescent bulbs they are more profitable. To give an example, a LED bulb is used for 3 hours per day and it has a lifetime over 20 years, where a fluorescent bulb with same input endures about one third of LED bulb. Additionally, the content of flourescent bulb is risky for human health. Since they consist mercury in it, the case of broken bulbs can cause Alzheimer, disorder of kidneys, immune system problems. Now you can both save energy and your life by choosing the right bulb option!