Last week I was tasting some Pinot Noir and I tweeted that I saw no reason for any Pinot to ever go over 15% alcohol.
This was an unusually absolute stance for me, because I tend to be a relativist on the issue of alcohol. If a wine is balanced and doesn't taste hot, I won't mark it down solely on the numbers.
And unlike some Californiaphobes, I will drink wines over 15% alcohol, particularly Zinfandel, which is notoriously high in sugar.
However, not all grapes are equal. I'll try a Grenache with 15.5% alcohol, but I wouldn't consider drinking a Chardonnay at that level, and they exist.
Here is my rough guide for what the alcohol range of different varietals should be. Generally, the highest number is there to accommodate ripe but balanced wines from California or Barossa Valley; the rest of the world really shouldn't be at the edge.
Cabernet Sauvignon: About 12.5 to about 14.7%. Cab is the grape that makes me want to say "15 is too much." There are good wines higher than 14.5%; Shafer mysteriously makes all of its wines at 14.9% alcohol (taking advantage of the 1% tolerance in the law), and they're nice. But most Cabs over 14.7 are too big, too hot, and too uninteresting -- the grapes got so ripe that they lost their complexity. As for the low end, Kermit Lynch once showed me a bottle of Ridge Monte Bello Cab from the early '70s that was under 12%, and check out the 12.5 on the Diamond Creek bottle in the photo. That said, these days anything under 13 is really unusual and probably a manipulated corporate product.
Merlot: About 13 to about 14.5. Merlot needs to be ripe, but should be soft and approachable. I might drink a glass of 14.9 Cab without food. I don't see why the world needs 14.9 Merlot.
Pinot Noir: About 12.5 to about 14.4. The upper limit cuts off some Santa Lucia Highlands Pinots, but if I want a red wine that big I'll order Grenache. Making Pinot grapes into wine above 14.5% alcohol is putting a round wine into a square peg.
Syrah: About 12.5 to about 15.5. The upper level is purely for Barossa Valley, but I have had some great Shirazes with balance at that level. However, if you want to taste the grape at its spicy, feral best, you need to get it at about 13.5 from the coolest climate you can.
Grenache: This grape can handle some heat. I'll drink it from about 13 -- when it tends to be light and spicy -- to as high as 16, when it's ripe and full-bodied. Robert Parker has given huge scores to Grenache-based wines with higher alcohol than that, and I'll acknowledge that they taste good, but I'm driving. Seriously, if you want a good high-alcohol wine, look here.
Zinfandel: Zin has its high-alcohol reputation not just because ripe wines can still be balanced, like Grenache, but because the clusters of grapes ripen unevenly, so that lower alcohol versions tend to be pretty bad. It's rare to have good, unmanipulated Zin below about 14% alcohol. However, I start losing interest above 15.5.
Chardonnay: One of my gripes with many wine and food writers is the old saw that "wine is meant to serve with food." What if it's not? There's nothing inherently wrong with having wine as a cocktail, which many Americans do. That's the best use of Chardonnays over about 14.2% alcohol. I prefer Chardonnay from about 13.3 to 14% -- a pretty narrow range, because less than that is usually underripe or alcohol-reduced. But I'll drink it up to about 14.5%, though usually without food.
Sauvignon Blanc: The whole point of this grape is to keep it lean and refreshing. I like it as low as 12.3%, and don't see any reason to drink Sauv Blanc over 14%.
Riesling: Is there a grape with a lower limit or a wider range? I've had delightfully complex Rieslings at 7% from Germany and 14% from Australia. I don't think you'd want to switch countries with those numbers.
Pinot Grigio: Lately in our rush to make everything bigger, I've seen Pinot Gris/Grigio with alcohol befitting a Cabernet. This is a mistake. Like Sauv Blanc, the point of this grape is to be refreshing, even the more complex Alsatian versions. I'll drink it as low as 12.5 but if it's 14, I don't want it.
Viognier: You want a boozy white? Pick this one. It's naturally high in sugar and while I've had good ones as low as 13, it tends to peak in the 14s, and is the one white that I will drink all the way up to 15, though not higher.
Rose: Why would I want a pink wine at 14.5% alcohol? It's not against the law to chill red wine. If that's what you want, drink that. Roses are best from about 11.5 to 13.5, and I'll rarely drink one above 14.