A low-cost, efficient, high intensity LED luminaire (HILL) assembly for use indoors or outdoors in wet, damp, or dry environments. In various embodiments, the HILL assembly can be powered by a universal AC or a DC electrical supply and can operate in a temperature range from about −40° C. to about +85° C. The HILL assembly can include a lens element comprising one or more concavo-convex lenses; an interchangeable LED module comprising a plurality of LEDs positioned in a LED array; and a heatsink housing containing a power supply for the LEDs. The HILL assembly can optionally comprise a circuit board for the LED array that employs thermal via technology, a lens with a frosted lip for attenuating the light source as seen from an angle, and/or a sensor for sensing an environmental parameter of interest. Driver circuitry and the LEDs are preferably mounted directly on a common circuit board.