Does a 300watt halogen bulb use as much electricity as 3 * 100w ordinary bulbs?
Yes, it does use that much electricity. These bulbs don’t usually have particular long lives, so waiting for it to burn out before you toss it would be fine. If it lasts 100 more hours, that’ll run you about $3 in electricity. That’ll give you time to come up with a new lighting solution. When you throw it out, it’s not particularly bad for the environment. It’s mostly glass, aluminum, and a bit of copper and tungsten. Nothing notably toxic. The new bulbs, however, all contain mercury. I hope rules are made to prevent them from going in the trash. Just like you return a lead-acid battery before you buy a new one, maybe the big stores will have a bin to put them in when they quit working.