[oil pan 4]

I assume it might be worth it. Only expecting it to be say 10 to to 25 watts per wheel. I would be surprised if it saved more than 200 watts on all 4 wheels. In a perfect world with perfect brakes that never drag this would not be anything to consider. If they only save 100 watts definitely not worth it. Or they save 200 watts might be worth it over the life of a set of brakes.

According to Wikipedia the brake drag dynamic friction coefficient of brake pads is between 0.35 and 0.42u.
That means 1,000 newtons of brake force is countering 350 to 420 newtons of friction.

Math is a universal language and units are interchangeable so it come down to preference. So I self identify with units of imperial.

So if we know u, then we need force and distance so we can determine speed, once we know speed we figure power.

To get force simply take a measurement of how much the spring will be compressed, (hint: you may want to stretch the spring to a longer free length to get more force) then put the spring on a scale and measure the amount of force at target compression. I didn't actually do this last time but I have a set of springs in the mail, should be here today and I will measure them. So I will edit in an actual value later it's only going to be several pounds of force.
Worst case scenario I have to use the scales at work.

To get distance just measure the mean radius, or just measure from the center of the hub to as close as you can to the middle of the shinny area. You want the actual area of rub. This doesn't need to be high precision. For the rear of the leaf it's about 5 inches to the mean pad to the rotor rub area. So circumference is about 15.7 inches

Now we need speed. Go over to tirerack dot com, look up your tire make, model and size, go to specs and they have number of rotations per mile listed. For a leaf size energy saver A/S thats 836 revs per mile. I drive about 65mph so let's round that to 905 revs per minute, need it in units per second.
So the brake pad is covering about 19.73 feet of mean rotor circumference per second at 65mph.

If the brake pad drag reduction clips can reduce what seems lile a lot of drag lets go with what I think will be a high number of say 9 pounds off the pads, reducing let's say 3 pounds of force off the pads drag, that's 59.22 foot pounds of energy per second per wheel with that size brake rotor at that speed. Or 7,107 foot pounds per minute for the rear axle per minute at 65mph. That's substantially more than what I thought it would be.

Conversion of foot pound seconds to watts is
foot pound seconds /0.7376

So that comes out to 80 watts per back wheel. The fronts will be little more since they are bigger.

If we round all 4 wheels to 400 watts that's pretty substantial. At 65mph I run about 10kw so that's about a 4% reduction in drive power should directly translate to about 3% or 4% more range.
This is a higher estimate but I will know for sure when I compress springs on a scale. So it will still easily be 200 or 300 watts for all 4 wheels.

When you buy a pack of these clips you get 4. Put 2 on each front caliper when I put them on the leaf because the fronts were a little sticky, then I was going to order more and put them on the back. But I forgot. So they're only on the front.

Level of skill required:
If you can accidentally poke your self in the eye with a wire you have the necessary skills.
A c-clamp and some linemans pliers help.