p>Electric baseboard heaters often make cracking noises, for example when they are turned on after a long shutdown, or simply when they start heating again when the air temperature drops below the temperature indicated on the thermostat. These noises are caused by the expansion and contraction of metal parts in the radiator as it goes through a heating and cooling cycle. </p> <p>So what you’re hearing is not dangerous, but if it is really irritating you, you could consider installing electronic thermostats if you currently have bimetal thermostats, electronic ones are are more sensitive and therefore more accurate. They may help by regulating the temperature better and providing shorter intervals between being active and inactive, and if they don’t cool as much before the next heating cycle begins it may reduce the amount of noise you hear. </p> <p>You will probably also be a bit more comfortable with electronically controlled thermostats on both ends of the spectrum - you may experience less overheating, and, your house won't cool as much before they kick in again. </p