I used to run all 500 watt halogens. They were really great and I liked the light but I would consistently blow 1 or 2 bulbs per night. I switched to 300 watt bulbs and have never blown one since. I decided the heat from the 500's was just too much for the bulb. The 300's were a little less light, but I quickly got used to it and have no complaints. I'd really like to try the ultra's. And by switching to the 300's I was able to get a smaller generator.