When a wine is balanced it has the perfect harmony of acidity, sugar, tannins and body. Generally speaking a wine that is medium bodied will have medium tannins and/or sugar making it balanced. Though there can be balance in wines with high sugar or tannins as well assuming they have the opposite components needed to gain balance.
There are the two groups that are opposite to each other where equality needs to be reached between them in order to gain balance. Fruit concentration and sugar make up one group and the other is acidity and tannin level. How these two groups work is – if a wine has a high fruit concentration it can be dry, but in order to gain balance needs either high acidity and/or tannin to gain a balance, and vice versa.
High Fruit Concentration Balance – an example of a wine with a high fruit concentration is a Barossa Valley Shiraz. The Shiraz grapes are from a very hot climate resulting in a high fruit concentration, and in this case there are also high tannins. These high tannins balance out the wine even though the acidity is only medium-low.
High Sweetness Balance – an example of a wine with a high sugar content is a Botrytis Riesling. The grapes used for this wine have higher than usual sugar content that can’t all be fermented resulting in a sweet wine. It is the acidity, in this case, which provides the balance against the high sugar content.
High Acidity Balance – an example of a wine with high acidity is Sauvignon Blanc. Most Sauvignon Blanc is grown in a warm climate that allows for the grapes to gain fruit concentration. Yet in the cooler vintages in the cooler climates such as Marlborough there will be a high retention of acidity (higher than usual) and the winemakers will leave a bit of residual sugar in the wine. There will be just a touch to make them dry-off-dry BUT the acidity is so high that it helps to balance out the wine and you don’t recognise it as being off-dry thanks to the drying effect of the acidity.
High Tannin Balance – an example of a wine with high tannins is a Nebbiolo (an Italian red grape varietal). In the case of Nebbiolo it has both a natural high tannin content and a high acidity content. Luckily it also takes a long time to ripen fully – this extended period of time gives time for the grapes to gain fruit concentration. This high fruit concentration helps to give the resulting Nebbiolo balance.