I have Firstsgear heated gloves and jacket liner. But then I would.
Heated gear isn't the power hog it used to be if you get good pulse type controllers (like the Heat-Troller). In the past, and still with some lower priced gear, the system pulled 100% regardless of what you were actually using to heat your gear. The rest was shed in wasted heat by the controller. This system type can easily overtax your Spyder's electrical system.
The 2nd method of heating, which is still used today in less expensive gear, is 100% duty cycle. You simply switch it on when you get too cold and switch it off when you get too hot. While this is better than freezing, I really don't recommend these. You will save some money but you'll never be happy with it.
Pulse engineering, though more expensive, is very efficient (which is very important on our anemic power output Spyders). Most of the time you will need only 10%-20% duty cycle to maintain a perfect comfort level. At a 20% setting, Pulse will send 100% heat for 20% of the cycle and shuts down completely for 80% of the cycle. You never notice the on/off cycle as it does this several times each minute.
All of the electricity is used to warm you up. None is wasted.
Here are some examples of probable and possible power consumption.
The heated jacket liner comes in a 65w and a 90w version. I recommend the 90w as they are the same price and too much potential is a lot better than too little when it comes to heat. Of course the 90w liner will use more juice and heat faster at the 100% setting, but you will use the same amount of power at maintenance level as you will with the lower watt model.
The Gloves are 30w per pair.
The Heated Pant Liner is 30w.
Heated socks are 18w per pair.
Most people are fine with gloves and jacket liner which at 20% draw (which is a very reasonable comfort setting) would consume 24w. At 50% draw consumption would be 45w + 15w = 60w. Cranked all the way up, which you might do for a few minutes to heat the system, power consumption would be 120w. But you won't be able to run this setting for very long. It will get uncomfortably warm.
You can double electrical draw for 2 riders with Gloves & Jacket Liner
20% x 2 = 48w
50% x 2 = 120w
100% x 2 = 240w
If you went with everything from gloves to socks your total 100% draw would be 168w. 2 up with everything running at 100% would be 336w. While this is quite a bit for the lower output Spyders like the RS, you won't be running this level for more than a few minutes before you will be forced to turn it down to the more normal 10%-20% maintenance setting. A few minutes of high current draw is not going to affect your Spyder if the electrical system is operating correctly.
And typically, the rider, after reaching comfort level, will use only 30%-50% of what the driver needs to keep warm.
So realistically, even if you're running 2 up with all the possible heated gear options in very cold conditions, it is likely that your continuous draw would be no more than 30% or about 100w. Not much more than a pair of HID headlights.
You can double electrical draw for 2 riders with full gear
20% x 2 = 68w
50% x 2 = 168w
100% x 2 = 336w
What you do not want to do, regardless of which system or what you are riding, is to plug in and crank up the heat with your Spyder not running. You want to start your Spyder and then turn the heat on.
Nor do you want to idle for any long period with 2 people running heated suits at 100%. With just a bit of common sense you will have no problems.
Unless you experience cold feet or legs (usually knees get it first) I recommend getting heated gloves and jacket liner and see how that does you. You'd be surprised how much it helps the rest of your body to keep your core and hand temperatures warm.
Then if you experience cool feet or legs, add these components.
There are also heated stand alone jackets and heated glove liners.
And new for this year from Firstgear is their passive 'Heat Pump Vest' which greatly increases insulation and body heat retention.
You can see the full line of Firstgear heated clothing here. And as mentioned, there are several other brands that offer heated gear as well.
http://www.firstgear-usa.com/heated.html