10% is about right as a working number, but the fact that the cold itself will reduce range anyway makes it difficult to compare directly. My snows, Michelin X-Ice Xi3's, are *much quieter* than the stock A/S Goodyears, quite an unexpected benefit! The Blizzaks I had earlier were indeed much louder on dry pavement. Additionally, while my impression is that the 'zaks are best in deep snow, the X-Ice is far better in salty slushy ice driving in 'burbs more typical of my use.About 10%. They are also a lot noisier, at least the Blizaks that I have are. Snow tires are a necessary evil for the Volt because it's FWD not AWD. When the first snow storm hit after I got my Volt I found that I couldn't get out for the driveway of my local Agway because it was on a slight incline, I had to back up and get a running start. I immediately ordered a set of rims from costco.com and when they came I bought a set of Blizaks at Costco, unfortunately Costco doesn't stock rims and they won't even deliver them to their stores, they get delivered to you and then you have to take them to their store to get the tires put on and mounted.
*nod* I get a few miles BACK on my range after putting the snows on. Winter rubber composition helps a LOT on rolling resistance, compared to the "all-season" Bridgestones.10% is about right as a working number, but the fact that the cold itself will reduce range anyway makes it difficult to compare directly.