To go from 18 volts down to 12 volts means that you are dropping 6 volts in the regulator circuit.
The 6 volt drop will be converted to heat (conservation of energy physics).
While I don't know a whole lot about practical applications of electricity, my understanding of electrical energy is that volts, amps and resistance are directly related to each other. Yes, energy in an electrical circuit will create heat, but dropping voltage down doesn't lose all that energy to heat. It can be achieved by decreasing the resistance or by decreasing the amperage (V=ir) or both. You don't simply give up the energy by dropping the voltage.
If, to use an imperfect analogy, water flowing through a narrows was electricity, voltage represents the force that water exerts on a resistance to that flow, amperage is the rate of flow (how fast the current), and resistance is the restrictive width and depth of the narrows (how much work is needed to push that water through at the rate it is going).
Perhaps, if the regulator were designed inefficiently, it might generate excess heat and not preserve the V=ir relationship. But, if the amperage is maintained and the resistance is lowered, a voltage drop would be experienced with less heat generated than the original circuit. This is tantamount to widening the narrows. If the current is slowed in the same narrows, again, a drop in force (voltage) and less heat generated.
I'll concede that most of what I know about electricity was learned in classes on theory for small circuit electronics. I have almost never had to do more than rewire my house to add a couple of sub panels and split 220 ac down to 110 ac.
I only know, the examples of voltage regulators I've seen on the market were inexpensive and fairly simple devices. I have no experience working with them and little practice thinking like an electrical engineer.
Take this as you will, but I believe in what I'm saying.
- Will (Dragonfly)
