A wine cellar is a room, or in some cases cabinet, meant to store and protect wine. It can vary in size, cost, and effectiveness. In recent years a number of affordable options have appeared on the market, allowing even casual consumers of wine the ability to store their wine.
Intended to protect the wine, a wine cellar can guard against the three traditional enemies of wine in bottle: heat, dryness, and light. A good wine cellar keeps the wine at a fairly low temperature, with a decent amount of humidity, and in relative darkness. In addition, a good wine cellar protects against any drastic fluctuations in temperature or humidity, which can damage the wine very quickly.
The term wine cellar is often used to describe anywhere meant to protect wine for a prolonged period of time, but should strictly refer to an actual below-ground cellar. A wine cellar that is above ground is more properly called a wine room, and the smaller wine fridges many people use in their homes are wine closets.
Within the scope of an actual wine cellar, there are two main types: passive cellars and active cellars. A passive wine cellar would be found somewhere that is naturally cool and humid, and which also doesn't change wildly depending on the season. Deep natural caves are often used as passive wine cellars, but man-made earthen cellars can also function well in the right environment.
Active wine cellars make use of insulation, monitoring and cooling systems, artificial humidifiers, and seals. These cellars can be very costly, depending on their size, but allow for more dynamic construction. They may also be a more ideal form of protection for valuable wines.
A wine room or home wine cellar can be constructed either by a specialized company, or in a do-it-yourself fashion. Many people find that they can convert a spare closet into a functional wine cellar without spending too much money or time. The most important thing is simply to keep the wine cool, and at a steady temperature. Ideally, wine will be kept at somewhere around 50° F (10° C), with no more than a few degrees variation year-round.
Many companies now also offer small electric wine cellars, which are really wine closets or wine refrigerators. These come in many different sizes, and at a number of different price points. The smallest hold only a few bottles, while larger stand-alones may hold more than 100 bottles. The cheaper standup wine cellars regulate only the temperature of the wines, with some having two different "zones," one for red and one for white. More expensive standup wine cellars keep the wines at a constant humidity as well, which may or may not help protect natural corks from drying out and damaging the wine.
Some companies will also come to your house and convert a closet or spare room into your very own wine cellar. They install added insulation, temperature monitors, and some type of humidifier. Many consumers find that these conversions can be surprisingly affordable.
One other alternative to a traditional wine cellar exists for those who want to protect their wines, but don't want to invest in digging out their own cellar or finding a natural cave. Many self-storage facilities offer temperature- and humidity-controlled environments for a monthly price. This can be a surprisingly effective way to keep a large number of wines protected for years on end, although it is a good idea to make sure the temperature range is truly stable, and ideally to find a unit that offers some sort of insurance for the goods that you store there.