Dimmer switches are sold with different maximum wattages including 500, 600, and 1,000 for incandescent lights or 150 watts for LED lights. Calculate how many lights you can add to the dimmer based on the wattage per light, but do not add so many lights that the dimmer is at max capacity. You should also take into account the total electrical load of the circuit where you will be adding the lights, which is likely powering other appliances in your house as well. Most circuits are 15 amps and shouldn’t be loaded with more than 12 amps, which is 1440 watts at 120 volts. Find out what else is powered by the circuit where you are adding the lights by turning off the breaker and seeing what loses power. Then calculate whether your additional lighting plus the other appliances comes in under 1440 watts all together.