HID's do generate very little heat and they take far less electricity to run once lit. The catch on the lower power consumption is that it takes a very large amount of power to ignite the gases, and I've heard on some other online forums(I've been looking into HID's for my bikes) that the added draw on the electrical system can sometimes be enough to cause the bike not to start. The work around was to install an on/off switch(probably illegal) on the light, and then start the bike, and then turn on the light.
I have HID's on my car, and the low beams will likely be more than enough to light the road without a high beam. The other thing I will warn you though, is if that is a true HID and there isn't a projector to shape the light output(gives it that clean cutoff line), then you will more than likely have an illegal setup and also be a royal jack@$$ to everyone else on the road since you will be blinding oncoming traffic. I'm all for HID's when they are correctly installed, but I've been blinded by a number of pricks who just installed the HID bulbs into a halogen headlamp and hooked up a ballast.
Easiest way to test to see if it's a HID. Go out, turn the light on, and if it takes 1-2 seconds to fully light up, it's a HID. The HID's take a little bit to get to full brightness, so they will turn on dimly and then get brighter, and this is very noticeable.