Lights dimming when the air conditioner (AC) comes on can be a normal occurrence, especially if the electrical circuit or wiring in your home is not adequately sized to handle the simultaneous high electrical demand of both appliances.
Air conditioners, particularly central air conditioning systems or large window units, require a significant amount of electricity to start and run the compressor and cooling components. When the AC compressor kicks on, it draws a sudden surge of power, which can cause a temporary drop in voltage in the electrical system. This voltage drop can result in lights flickering or dimming momentarily.
In most cases, this dimming effect is harmless and does not indicate a serious electrical problem. However, if you notice a significant and prolonged dimming of lights whenever the AC turns on, it may be worth having an electrician inspect your home's electrical system. They can ensure that the wiring and electrical components are appropriately sized and can handle the electrical load without causing any potential safety issues.
It's worth noting that newer homes or those with updated electrical systems typically have circuits designed to accommodate the high starting currents of appliances like air conditioners, reducing the chances of significant light dimming. If you are experiencing frequent or significant dimming, it may be beneficial to consult an electrician to evaluate and address the issue.