You'd think something as expensive as a BMW with heated grips would offer a variable option. I've just got some Oxford heated grips I paid about 100 for at MotoLiberty in Dallas. They come with 5 settings, but you have to wire them yourself (you can go straight to the battery for power if needed since they have an auto shut off feature). The settings are: low, med-low, medium, med-high and high. I think its like 25% for low, then 50% for medium, 75% for med-high and 100% for high. I can't remember what med-low would be in power percentage. Something like 35%. I could always just go look at my bike in the garage, but I'd have to get up to do that.
Cheaper on Amazon if you look around, but here's a Revzilla link for reference.
Crank up the heat with Oxford Premium Heaterz Grips. Choose between five different settings and focus on the road ahead, not how darn numb your finger…
www.revzilla.com