[quote=“tom sawyer”]You can never have too much brewing stuff after all.[/quote]Amen brother!
As to water use, you can always recirculate water and run it through ice (I do that in the winter to avoid an icy driveway) - applicable to both methods. Also in the winter, making the ice is as simple as leaving water containers out overnight.
I can clean my IC pretty fast, so that is why I use it… I have considered the plate chiller to speed up the chilling, but the cleaning time seems to add back a fair amount of time/effort.
Efficiency is very dependent upon the specific design of the chillers being compared, but there is no doubt that a well designed plate chiller or counterflow chiller will draw out more heat per unit cooling water used than a well designed immersion chiller will. The reason is that with a counterflow design, you maintain a temperature gradient across the entire heat transfer surface area that drives heat from the wort to the cooling water and results in hot water for the entire time of the chilling. When using an immersion chiller, the efficiency is good at the start of the chilling process, and gets very poor by the end.
Take a look at how post-turbine working fluid chilling is done at a modern power plant. They use plate chillers.
ps, I really, REALLY like my therminator.
A plate chiller is going to have a much, much higher surface area than an immersion chiller, but I don’t think that matters since neither is surface area limited if the flow rate is adjusted so that t_out ~= t_beer. Even if they were identical, the plate chiller is always going to be more efficient because the dT between the beer and the cooling water is always maximum. The exchange of heat, goverened by Q=mCpdT means that for a given unit mass of water, the thing with the higher dT is going to transfer more energy. As the immersion chiller cools the beer, the temp of the cooling water and the beer get closer and closer, so it takes more source water to cool the beer by another degree. This is going to be more evident for those with high ground water temps, mine tops out around 85F in the dead of summer.
The immersion chiller can be made more efficient by recirculating (this is not necessary in a plate chiller because the flow is already turbulent for the target fluid) and by slowing the flow as the dT gets closer. Also, something like 70% of the water used in an IC is to get the beer down that last 20°, so if you can stop the chiller when you have a 20°F delta to the source and finish the job with ice or the fridge, you’ll be golden. I use an IC and throw it in the fridge overnight, or if it’s really hot I’ll run ice water through the IC after getting close.
Here’s a simple graph for cooling a unit mass of water with a IC from boiling to 66F, with 65F cooling water. I just calculated the amount of energy required to cool a unit mass by 1°F, then divided that by the (dT*Cp) at each 1°F to see the mass of source water necessary to transfer that much energy. The x-axis is the dT between the source and beer, and the y-axis is the % of the total water used if cooled all the way down to 66. This is only an approximation of the total, and in the real world there will be some efficiency loss due to incomplete heat transfer, but you can get the idea.
Considering that I can get a 5 gal batch down (usually a little too cold) in less than 15 min using a IC that dosen’t even flow that great (read - it has a kink), I juast cant see spending the money for another type chiller. Not saying i wouldn’t use one if i got if free (like I did my IC chiller), but I am a cheap SOB so. Now if we were talking about a huge taste differnce it would be a different matter, but I suppose I am cheaper than I am lazy 
Barry
IMO, the plate vs. immersion chiller decision comes down to two issues. First and foremost, water supply temperature. If you have a cold water supply temp, an IC will work well. If you have a warm water supply, a plate chiller may serve you better due to greater efficiency (assuming proper design). Second, but equally important, water supply availability. If you live where water is plentiful and inexpensive, an IC is nice in the simplicity of design and ease of maintenance (rinse & boil 15 minutes). But if you live in the desert or where the water supply is restricted, a plate chiller is more stingy and probably makes more sense.
I can’t comment of what uses less water. I used my counterflow a lot for a long time, I liked using it in combo with a thrumometer and with a few minutes of tweaking I could get the right temp wort to my fermentor. Lately though, I’ve returned to my IC for ease of use (set-up/no temp tweaking/cleaning/etc.) and the fact that I don’t have to worry about my homegrown hops clogging the works, cold break stays in the kettle, and its just plain easier with my 15-month old son’s needs.
