A modular intake heater (10) for an internal combustion engine. In one embodiment, the heater includes a first holder (14), a second holder (16), a heating element (18) coupled to the first holder, biasing means (34) for urging one of said first holder and said second holder away from the other of said first holder and said second holder, and a retainer mechanism (20) coupling the first holder to the second holder against the urging of the biasing means. In another embodiment, a heater (510) includes a first heater sub-assembly (519), a second heater sub-assembly (719), an access panel (511) coupled to an intake (512), and a retainer mechanism (515) coupling the first heater sub-assembly and the second heater sub-assembly to the access panel.