As an expert sommelier and brewer, I can confidently say that purchasing wine by the bottle is generally more cost-effective compared to buying it by the glass. This is primarily due to the fact that wines by the glass are priced higher per serving to account for the potential waste that occurs when a bottle is opened.
When a bottle of wine is opened, it begins to degrade and its flavors and aromas start to diminish. This degradation process is accelerated by exposure to oxygen, which occurs once the bottle is opened. As a result, the wine's quality and taste deteriorate over time.
Restaurants and bars understand this and take measures to minimize waste and ensure that each glass served is of good quality. They typically use preservation methods such as vacuum pumps or inert gases, like argon or nitrogen, to slow down the oxidation process and keep the wine fresher for longer. However, even with these techniques, the wine will still lose some of its original characteristics over time.
To compensate for this potential waste, establishments often increase the price per glass to cover the cost of the entire bottle. This allows them to recoup their expenses even if they are unable to sell all the servings before the wine becomes undrinkable.
So, while the cost per glass may seem higher compared to buying a full bottle, it is important to consider the potential waste that occurs when a bottle is opened. If you were to purchase a bottle and only consume one or two glasses, the remaining wine would likely go to waste unless you have a preservation system at home.
It's worth noting that there are some exceptions to this general rule. In certain establishments or situations where high-end, rare, or limited-production wines are offered by the glass, the price per glass may be significantly higher than the average bottle cost. This is because these wines command a premium due to their exclusivity and limited availability.
While buying wine by the glass may initially seem more expensive per serving, it is important to consider the potential waste that occurs when a bottle is opened. The higher price per glass accounts for this waste and ensures that each serving is of good quality. However, if you plan to consume multiple glasses or share with others, purchasing a full bottle is generally the more cost-effective option.