What should the ABV be?

So I'm brewing John Palmer's Cincinnati Pale Ale for the third time. Why? Because it's cheap, I like the way it tastes, and it's helping learn to brew. (Don't worry I have brewed other beers!)

All three times the ABV comes out kind of low, around 3%. Now the recipe calls for an OG of 1.045. On this last batch my OG was only 1.041. I didn't get all of the DME and LME into the boiling pot. I'm going to weigh out more next time (yes I will brew this again) to account for some loss.

I'm using Safale US-05 yeast that I rehydrate before adding to the chilled wort. I get health yeast activity easily within 24hrs.

I'm aerating my wort using a aquarium pump. I only aerated for 5 minutes.

My question is what should I expect the ABV of this beer to be? If my brew is coming in significantly lower than expected, what could be some of the causes?

Thanks!

 

I suppose a follow up question is is there a reason I should use two packs of yeast instead of 1?

 

First off you need to get all the LME and DME into the boil pot. Weighing out more won't help unless you get it into the pot.

When you use dry yeast you can aerate...or not. The results will be about the same.

 

ABV will always be dependent on your wort fermentability and the yeast's attenuation level.
You can estimate beforehand but the best way to know for sure is to measure gravity properly before and after fermentation.
US-05 is a vigorous yeast if healthy and can attenuate a highly fermentable wort a bit more than what the manufacturer's label description actually states. Individual yeast strain attenuations will vary, though.
For beer done with US-05 I would generally say 80% of your original gravity can contribute to your ABV level, so anything up to or just slightly near 4% wouldn't be unexpected..