Low OG due to not getting a rolling boil?

I've done 2 partial mashes now, and I've gotten a very low OG (about 0.010 lower than estimated). When I did extract brewing, I would boil (rolling boil) about 2.5 gallons of wort; with partial mash, I'm barely boiling (no rolling) about 4.5 gallons - my stove top just can't get that much wort to a rolling boil. I understand this affects hop utilization, but would it affect my OG?

Most likely, yes because you are not evaporating out the proper amount of water to condense the wort over the same amount of time. You really want a nice boil to concentrate the wort

There are also mash efficiencies to take into account as well but first you need to get a proper boil and see how it turns out and go from there

5 gallon batches? If so then you're not doing a full boil which I would recommend with partial mashes. Adding water will dilute your og. So you want to start with a pre-boil volume and boil down to 5 gal or down to your desired gravity. Most people don't have a stove in their house that can handle full wort boils (especially people like me with electric stoves). That's why typically full wort boils are done outside with propane burners. Not getting a rolling boil would not evaporate enough wort within the hour to concentrate the sugars and could cause low og but it sounds like your not starting off with enough water anyways. So you could be suffering from low extraction efficiency. Not getting to a rolling boil will also put you at risk for too much dms in your beer (a violent boil is what drives this compound off).

I find that using two pots overcomes the heat limitation of brewing on an electric stove. I use two cheap 12qt. stainless pots from a dollar store. I fill the pots alternately while lautering. The one on the bigger element comes to a boil a few minutes more quickly than the smaller one, which works out nicely. You don’t want two pots to both start boiling at the same time.

This method nearly doubles the heat, and the smaller pots fit the burners better. I used to use a 16 qt. pot, but it took forever to boil, and my batch was like 3 ½ gallon. Now I get a bigger batch ( 5gal) in less time.

The rule of thumb on the boil is to boil off at least 10% to minimize DMS.

Thanks! The double pot idea is a great idea. Cheers!

I use a 34 quart pot on an electric stove and get a good boil by wrapping the pot in reflective insulation like you would use to insulate a heating duct. Works great. I start off with 6.5 gallons in the pot and it takes about 40 minutes but it boils nicely.

A "heatstick" will also allow you to boil large volumes stovetop...try a search.