Since we are taught not to use a microwave to heat baby bottles or baby food I decided to get a bottle warmer. I only looked at and purchased this one. This was the only one at the store and I didn't need anything real fancy. The looks alone caught my eye just because purple is my favorite color.
After you put the bottle or jar of baby food into the warmer you fill the warmer with water. The amount of water you fill it with is according to the size of the bottle. If the bottle is a small bottle you fill the warmer to the top of the milk. If the bottle is a large or 8oz bottle you fill the water to just below the rim of the warmer. Either 1/2 inch or 1 full inch below the rim I think. Then when it is plugged in the light will turn red. After you turn the knob on the red light will turn green. There are 3 heat settings one, two and three. Three warms the substance the quickest. When the water is heated the green light will start flashing red and green. This only means the water is being maintained at that heated level. There is a small chart that helps to determine what setting to use and for how long. It only take around 2-3 minutes to get the chill off of a refrigerated item. If you want to actually warm the substance it will take a little longer around 5 or 6 minutes.
I however don't have much patience so I fill the warmer with warm tap water which cuts the time I have to wait. I also leave the water in the warmer at all times. That way during the night I only have to insert the bottle and turn the knob.
On 2 occasions where I have been sleep deprived I have left the bottle warmer on during the night. The next day when I noticed the warmer was still on all the water was evaporated and the warmer is of course warm. I then unplugged it and let it cool off. Suprisingly both times it has still worked. I personally think this warmer works very well and I will use it again if I ever need it.