The 11 LED lights are on a different circuit branch than the 4 LED lights.

The total load on each branch is different.

I'm assuming that all 15 lights are identical.

They are identical lights and they are on the same branch circuit wired to two different dimmer switches. I have installed led lights in several locations in various configurations, and I am always able to dim them to around 25 % output. These four only go down to about 75%. Think I should change the dimmer and see what happens?

By branch circuit do you mean the circuit from the breaker?

The ability to dim depends on the min load requirement for the dimming switch.

11 lights will be a greater load than 4 lights.

You can try changing the dimmer.
Lutron dimming switches should be able to support dimming for down to 1 lamp per circuit.

both switches are on the same circuit breaker. I can turn on both switches (all 15 lights) and dim the 11 down to about 20%, but the four on the other switch only go down to about 75%. I can turn off the switch with 11 lights and the four lights still don't dim any more. I turn on only the 11 lights and they still dim down to about 20%. Doesn't seem to matter what the "draw" is.

There are 2 sub branches, each forming a distinct circuit. Otherwise, one switch would control all.

The power feed to both branches is common. Branch A has a certain number (- say 11) of lights downstream of a switch which happens to have dimming capability. Ditto for branch B, except that it controls 4. The load on each is different

Thanks davidtay. So, I guess it's the load to each switch rather the load to the breaker that makes the difference. Therefore, turning on all of the lights doesn't make any difference. I've run two lights on a switch before and they dimmed okay. If the load or number of lights to the switch made a difference, then it would seem that one light to a dimmer would hardly dim at all. Again, maybe I should just try changing switches. I can't think of anything else.

You might want to try a lutron dimmer made for led lights. Eg Diva CL

Older dimmers like the Leviton Monet have a min load rating that would only be met with a large number of LED lights.

Thanks, "David". I may just let them go as is. I installed all of these in my sister in law's house, and she is stoked regardless of how they dim. I don't think she knows the difference. If I ever change the switch, I will let you know what happens.

ken

You don't say what type of dimmers or LED's you have.

I would unscrew 7 of the 11, and see how the remaining 4 dim compared to the other dimmer.

Some dimmers have an adjustment behind the faceplate, so that you can set the minimum dim level. If your dimmers have that, they may not be set the same. On mine which do, it is a little slide or wheel.