For anyone curious, here is a Watts to BTU converter:
Watts to Btus (IT)/Hour Conversion Calculator
Someone suggested the #SR1151 model to me:
sr1151-1262f-1 However, it is 1,500W which is equiv to 5,100 BTU .. which seems like it would take forever to get 5gal to a boil.
However, BTUs on gas are hampered by a low efficiency - about 50%. Whereas induction is 85-90% efficient (depending on who you ask). So, a little math to appease the beer gods:
BTUs/hr = lbs water * temperature rise
8.3 lbs water / gallon
212F boiling - 70F starting = 142 F rise
Let's say we start at 6.5 gallons for a 5 gallon batch. So:
8.3lbs water / gallon * 6.5 gallons * 142F = 7,660 BTUs to boil in 1 hour.
Now, assuming 50% efficiency on a gas burner (and that is high, they are usually rated at 30%) means 7,660/50% = 15,321 BTU's to boil in 1 hour at 50% or 25,536 BTU's at 30% efficiency.
While induction is 90% efficient. So 7,660/90% = 8,512 BTUs to boil in one hour at 90% or 9,012 BTUs at 85% efficiency.
Okay, that is a huge difference [thinking outloud with fingers].
So, I need between an 8,500 and 9,000 BTU induction burner to boil 6.5 gallons within a reasonable time - and probably up to 12,000 BTU if counting for heat loss. So, at least 2,500W burner.
Now, Menu System (Swedish:
:: MENU SYSTEM :: Induktionsherde - Induktionskochgeräte) does put out a standalone induction hob that puts out 6kW (6,000W) which is 20,472 BTUs. Using my calculations above, that hob should bring things to a boil in around 30 minutes.
But, what happens when I move to 10 gallons? That's 8.3*10*142=11,786 BTU's; and let's say 80% efficiency [the Menu System burner is rated 50-90%] then 14,732. So, full boil in about 45 minutes. I could live with that.
Anyone else have any thoughts on this?