Without GregTech (9x UUM at 166,667 EU per UUM): 2 hours and 36 minutes to break even
With GregTech (9x UUM at 16,666,667 EU per UUM): 10 days, 20 hours, and 25 minutes to break even
With GregTech if you get your iridium from elsewhere (2x UUM at 16,666,667 EU per UUM): 2 days, 9 hours, and 52 minutes to break even
All of these numbers assume it never rains and you always sleep through the night so the ASP is generating 8 EU/t constantly.
I mean, yes, the ASP needed a nerf, but this is too extreme. With GT, even if I get my iridium from ores or bees, it's still going to take nearly 58 hours (in the best-case scenario) before the ASP stops being a net negative. If I play Minecraft for 2 hours a day, it will take a month.
As others have said, Greg didn't want UUM to replace mining, which is why he nerfed UUM and added iridium/platinum ores to the worldgen...which means that when you make UUM an essential crafting ingredient of something, you dramatically throw off the game balance for everyone who uses GregTech.
I understand that you probably intended to balance it for "vanilla" IC2, and that's fine. But look at it realistically for a minute: The vast majority of people who play modded Minecraft right now are using Feed The Beast. There are three FTB modpacks that include Advanced Solars...and all three also include GregTech. So, while I'm sure there are some people out there who are using vanilla IC2 + Advanced Solars and happily breaking even at the nicely balanced 2.5-hour mark, those people are likely a small minority compared to those who are using your mod in conjunction with GregTech.
"I added a config option" is fine and dandy, but your mod should be usable by and balanced for the vast majority of your users by default.