As I persist in winter riding I thought that I may treat myself to a pair of hand guards.
Any recommendations for heated-grip-compatible hand guards on my California 1100i?
Barkbuster stormguards are worth a look , they are expensive but easy to fit , and fairly robust .
I have a BMW 1150GS, I bought hand guards years ago, mainly for the looks. They are not designed for keeping hands warm, if anything the wind deflection on the finger tips makes it worse.
You need Muffs, I have urbano tucano ones.
Takes some getting used to, as hand controls are fully enclosed.
When fitted, I wear summer gloves in winter. If I wear winter gloves, I can barely feel the heated grips.
Also good in wet weather, as even waterproof gloves tend to transmit the cold when having water thrown at them.
Couldn’t disagree more, maybe it’s down to type of guards you fit. Muffs are a real pita, especially if you’re using a vee wipe in wet weather. I’m happy riding all UK conditions with hand guards and hot grips. I just buy the cheapest guards I can find and then mod them to clamp on with the mirrors or even the lever pivot bolts.
For what it’s worth, I put cheap eBay hand guards on the Ural. They do cut down the wind-chill. As for rain, it usually takes longer for my gloves to get wet, so must be helping there too. Took them off once (was supposed to be summer time) then instantly regretted it (at next summer downpour) so they went straight back on! 
NB: the type I have also need a bar end weight or similar in the ends of the 'bars with a central securing screw.
EDIT: come with their own plastic end plugs if no bar end weights to start with.