The electric bill will spike a bit, but thankfully its only for about an hour every month or so.
The "dimmer" capability is accomplised by selectively turning ciruits on and off. While I have 5 heaters, they do not all have to run at the same time. I can simply run 2 or 3 or 4. Also, I will be able to fine tune the heat actually transferred to the vat by raising or lowering the vat into the water bath. This adjusts the surface area of the vat that is getting heated. The vat itself, is on a block and tackle that is used to raise and lower into the bath water.
Why do all this? I have found that one of the most difficult aspects of cheesemaking is simply temperature control. Sounds simple, but I have found that it is more difficult than it seems.
In terms of the volume of the bath water, this is a 100gallon water bath. When I get to the point of putting the 25 gallong vat in the tank, I will only fill it to 75 gallons or a bit less.