Actually, I was slightly wrong. Ener-G is potato starch. But pretty much the same thing. Here's Ener-G's suggestion for portion size:
How much Egg Replacer do you need to replace one egg?
One Egg = 1 1/2 tsp Egg Replacer to 2 tbsp of water. To replace egg whites use the same amount as replacing the entire egg, so One Egg White=1 1/2 tsp Egg Replacer to 2 tbsp of water. To replace the egg yolk stir 1-1/2 tsp Egg Replacer into 1 tbsp of water.
I'm pretty sure ground flax will work in this case.
\t1 tablespoon ground flaxseed plus 3 tablespoons warm water. (put in blender, blend until an egg-like consistency)
I have Ener-G and I use it pretty often, it works well in many recipes and it's really cheap compared to eggs. I was so hesitant to buy it because it was $8 or something like that... that was over a year ago and I still have about 30 "eggs" worth of powder. I like to use it in cookie dough so I can eat it raw