Ceramic Heat Emitters are ideal for 24 hour heat, as they emit no light and can be used throughout day and night to emit heat. They are made of porcelain and come with a standard E27 screw fitting, which should be used in a ceramic holder.
They come in a 25w and 40w option, depending on the size of the enclosure you are using. They emit infrared heat and give off a good warmth, so may need to be used on a thermostat to ensure this is safe for you and your pets.
This dark heat source can be used all round, and lasts for up to 5 years, so makes it great for small geckos and hatchlings.