DemoSystem.cs

[UpdateAfter(typeof(PowerSystem))]
public class LightBulbPostSystem
    : JobComponentSystem
{
    private struct AfterPower
        : IJobParallelFor
    {
        [WriteOnly] private ComponentDataArray<LightBulb> _outputs;
        [ReadOnly] private ComponentDataArray<PowerInput> _inputs;

        public AfterPower(ComponentDataArray<LightBulb> outputs, ComponentDataArray<PowerInput> inputs)
        {
            _outputs = outputs;
            _inputs = inputs;
        }

        public void Execute(int index)
        {
            var supply = _inputs[index].PowerSupplied;
            var request = _inputs[index].PowerRequested;

            var bulb = new LightBulb {
                Brightness = supply / request
            };

            _outputs[index] = bulb;
        }
    }

    private struct Group
    {
        [WriteOnly] public ComponentDataArray<LightBulb> Bulbs;
        [ReadOnly]  public ComponentDataArray<PowerInput> Inputs;
        public readonly int Length;
    }
    [Inject] private Group _lights;

    protected override JobHandle OnUpdate(JobHandle inputDeps)
    {
        return new AfterPower(_lights.Bulbs, _lights.Inputs).Schedule(_lights.Length, 128, inputDeps);
    } 
}