An LED light system has an LED light module for inserting into a standard fixture. The fixture has a housing and cover for sealing the enclosure. The LED module contains a shell or outer surface having a matching form factor as the housing for making physical contact with the housing over a sufficient surface area to provide good thermal contact. A substrate is mounted on a support structure. A plurality of LEDs is disposed on the substrate. A heat transfer agent or medium transfers heat from the LEDs to the housing. The outer surface of the LED module spreads the heat over its surface area and firmly contacts the surface of the housing for good thermal transfer. The heat transfer medium is made of a thermally conductive material such as aluminum or copper and formed to contact a surface area of the LED module.