[nyakavt]

I make all my beer on my electric stove.  Mostly 3gal batches with the occasional 4+.

Efficiency is largely about the bound water in grain (0.125qt/lb) as a percentage of the total water added.  If you want 3gal of concentrated wort from 10lb of grain, you could add 4.25gal of water in a no-sparge method.  We'll assume 90% conversion (I don't typically see 100%) of a 36ppg malt mix, so you'd have 10x36x0.9= 324points of sugar in your 4.25gal of water.  Since the grain holds 1.25gal, you'd get 3.0/4.25=70.6% of that sugar in your 3gal.  That'd be 3gal of wort at 229pts in 3gal or 76ppg.  Boil that then dilute in the fermentor to 5gal gal and you'd have a 1.046 OG beer.

Tom,

Keep in mind that the apparent absorbtion (.125gal/lb or 0.5qt/lb) also includes volume contributed by the dissolved extract.  This makes the true starting volume larger, and the efficiency somewhat lower.  Extract contributes 0.63 L/kg (.303 qt/lb) of volume.  So in the example above the 10 lbs of grain is 36/46.214 = 77.9% extract by mass (10% less if you consider 90% conversion), *10 lbs = 7.8 lbs of extract, *.303qt/lb = 2.36 qts volume.  The efficiency then becomes 3/(4.25+2.36/4)=62%, leaving you with 3 gallons of 1.067 wort or 5 gallons of 1.040 wort, per your method above.

A two runoff sparge would be somewhat more efficient, which can be important when dealing with higher gravity beers.

same as above but split the water so that there are two equal runoffs:

strike water: 11 qt
absorbtion: 10*0.5 = 5 qt
runoff 1: 11-5=6 qt
sparge water: 6 qt
runoff 2: 6 qt

e1=vout/vtotal = 6/(11+2.36) = 44.9%
v_left = 11+2.36-6 = 7.36 qt
e2=vout/vtotal = 6/(11+2.36-6+6) = 44.9%
etotal=e1+(1-e1)*e2 = 44.9%+(1-44.9%)*44.9%=69.6%.

total collected: 6 qt + 6 qt = 3 gal
gravity: .696*324/3 = 75.2 points in 3 gal, or 45 points in 5 gal.

As far as how much a difference this is vs. a full volume boil, you could get about 88% efficiency with a two sparge collecting 7 gallons preboil, which would yield 5 gallons of 1.063 wort at the end of the boil for the same 10 lbs of grain.  Or to put it another way, you can get the same 1.045 wort by using 7 lbs instead of 10.  Not a great example, however, since you'd probably want to back off on the efficiency for quality reasons at this point.

[bluesman]

If you are limited to the stovetop method, I recommend substituting some quality extract to get the desired gravity points. If you add 20% of your desired gravity in extract to the boil you won't be so constrained by the mash. Obtaining good quality fresh malt extract is the key to making quality beer. I don't think you'll even notice the difference if you keep the overall gravity contribution in the 20%+/- range.

[afacini]

Maybe look into building (or buying, if possible) a heatstick to aid your stove.  Here's something to get you started.

This is excellent and probably much more viable than propane in my current location, thanks.

If you are limited to the stovetop method, I recommend substituting some quality extract to get the desired gravity points. If you add 20% of your desired gravity in extract to the boil you won't be so constrained by the mash. Obtaining good quality fresh malt extract is the key to making quality beer. I don't think you'll even notice the difference if you keep the overall gravity contribution in the 20%+/- range.

I'm knee-jerk averse to adding extract in my first runs with all-grain, but then again, I'm new to agb. What is a good way to predict your gravity in terms of adding X, Y, Z base extract? Any suggested rule-of-thumb?
(I'm assuming you recommend extract only if I end up needing to boil less than the final volume)

[bluesman]

If you are limited to the stovetop method, I recommend substituting some quality extract to get the desired gravity points. If you add 20% of your desired gravity in extract to the boil you won't be so constrained by the mash. Obtaining good quality fresh malt extract is the key to making quality beer. I don't think you'll even notice the difference if you keep the overall gravity contribution in the 20%+/- range.

I'm knee-jerk averse to adding extract in my first runs with all-grain, but then again, I'm new to agb. What is a good way to predict your gravity in terms of adding X, Y, Z base extract? Any suggested rule-of-thumb?
(I'm assuming you recommend extract only if I end up needing to boil less than the final volume)

Adding malt extract to supplement your OG in an effort to achieve a targeted gravity is a perfectly viable method of brewing quality beer. If you lauter 3 gallons of 1.060 wort and want to brew 5 gallons of beer with a final gravity of 1.050. You would simply add some DME @ 45ppg or some LME @ 37ppg to help boost your final gravity to the desired 1.050.

After lautering 3 gallons of 1.060 wort, add 3 gallons of water and the calculated addition of malt extract to boost your gravity to the targeted range and boil the wort.

If you want recipe specifics just give me your known additions and I'll help you calculate the remaining ingredients.

[tomsawyer]

Nyakavt, thanks for catching the 0.125gal/lb, I knew that and I think I used it properly in my calculations but typed it wrong.  And I did neglect to account for the increase in volume for the soluble sugars.

I do know that for a 1.050 beer I can get about the same efficiency with no-sparge as I can with a single batch sparge.  It may be that I'm getting better conversion with the more dilute mash and thats compensating to some extent.  I'm sure there is more of a deficit as the gravity goes up.

[thomasbarnes]

Maybe look into building (or buying, if possible) a heatstick to aid your stove.

I brew on a gas stovetop and find that my electric heat stick is vital in getting quick, full rolling wort boils. Just make sure that the outlets you're using have GFI protection on them and that your fuses can handle the current that the heat stick pulls.

Also, make sure that your heat stick is submerged at all times once you turn it on. It can easily get too hot otherwise.

[skyler]

How hot do your burners get? In my old apartment in Portland, the electric burners got CRAZY hot - turning bright orange on high. I boiled 5-6 gallon batches with 2 burners on medium (the kettle fit over 1.5 burners). In my current place, the burners can barely boil enough water to make spaghetti, so I wouldn't bother ever trying to brew inside.

[noonancm]

I would agree with the suggestion of a heatstick. Jim Spencer of Basicbrewing a year or two ago did a radio and a video podcast on them and came up with the idea (I believe in the video) that it would be great to use if your main source of heat is a stove.

Me. I just use two heatsticks and get my boil.

[classic]

I use an electric stovetop and routinely bring 6.5-7 gallons to a boil in a crappy stainless steel pot.  I bought some Reflectix for $2 at the hardware to wrap the pot in and it works pretty well but still takes about 40 min to get to a boil.