Alcohol Content in Wine
There can be some confusion about the actual alcohol content in a bottle of wine, because what you see on the label isn't always transparent or 100% accurate; labels aren't always reliable, there can be discrepancies and this subject can seem like smoke and mirrors. Clarifying some points can help you make a more informed choice about the actual alcohol content in your bottle of wine.
ABV
Displaying the ABV [or Alcohol by Volume] of a wine is a mandatory requirement; this can be found either on the front or the back of the bottle, usually at the bottom of the label and is written as a numerical statement. It tells you what percentage of the wine is pure alcohol by volume.
Wines vary in alcohol levels from as low as 5.5% for some sweet wines, to 15% for table wines, and up to 22% for fortified wines like Port, Sherry, Madeira and Marsala.
The ABV is stated in multiples of 0.5%, but a leeway or tolerance [the difference between the ABV stated on the label and the actual ABV of the wine in the bottle] of 0.5% is permitted for still wines. Therefore, a still wine labelled with an ABV of 12.5% for example, could actually be 13%.
There is however an exception for wines with a PDO [Protected Geographical Origin] or PGI [Protected Geographical Indication] stored in bottle for more than three years, sparkling wines, liqueur wines and wines made from overripe grapes. These wines have a leeway of 0.8%.
Duty
In the UK wine labelling is overseen by the FSA [Food Standards Agency]. They are responsible for the authenticity of wines imported into the UK and these must meet their regulations, which are based on EU legislation.
Duty is charged according to the ABV of a wine; the higher the ABV, the higher the duty rate, which increases incrementally with each 0.5% of ABV. The highest duties therefore being imposed on wines with an ABV of above 14%.
So potentially producers could fudge the ABV they declare by 0.5% to avoid paying higher duty rates. However, laboratory testing must match within the 0.5% leeway and mislabelling can lead to fines and legal consequences, not to mention loss of trust for consumers. Reputable producers then are rigorous and precise about ensuring accuracy.
Alcohol Laws
If you're on holiday, it's worth mentioning that alcohol laws are different outside of the UK and the EU, with some countries being much more generous with ABV tolerances for wines sold within their own countries. In the USA the leeway is 1.5% for wines below 14% and 1% for wines above 14% ABV.
In Australia the tolerance is 1.5% for wines above 6.5%, so a wine labelled as 12% could be as high as 13.5% ABV.
Considerations
Evaporation and oxidisation can affect the ABV of a wine over time, but the alcohol does not decrease significantly as wines age - it's negligible and the wine does not become notably less alcoholic. It's the way that alcohol in wine is perceived that can change as the wine ages - this is particularly true of vintage ports where after 20-30 years the intensity of the alcohol does seem to lesson, even though the actual ABV is relatively the same - it's the flavour profile of the wine that changes with age, the ABV will be very close to what it was when the wine was first bottled.
Affects of Climate
It's worth noting that wines from cooler climates generally have less alcohol in them than wines from warmer climes - the more sun - the more alcohol! With global warming the ABV of wines has been creeping up, and nowadays wines with an ABV of 14% have become the norm.
The percentage may change with vintage variations. A warmer summer will increase the sugar in the grapes at harvest and this will inevitably lead to higher alcohol levels in the wine, just as a cooler year will result in wines with lower alcohol. So buying your favourite wine one year with an ABV of 13.5%, may result in the same wine being 14% or 13% the next. Retailers may not always change this small piece of information on their websites [and wineries themselves for that matter] in time to correspond with the new seasons arrivals, causing more confusion for the consumer.
Having said this, many winemakers are concerned about the rising alcohol levels in wine due to climatic conditions and are taking steps to address this as consumer's tastes shift towards less alcoholic wines.
Choices
So if your preference is for wines with lower alcohol levels look to cooler wine producing countries like Germany, Austria and the UK, or the northern parts of a country - the north of Italy, Spain and France for example, as opposed to their southern counterparts.
Consider that white wines are usually less alcoholic than reds. Some grape varieties like Shiraz and Zinfandel produce higher alcohol wines because their sugars are naturally higher.
If you have a sweet tooth - then German eisweins and Canadian ice wines could be you answer and for sparking wines Italian Moscato d'Asti come in at less than 7%!
Also remember that when you cook with wine, the alcohol will reduce.