The following examples are intended to compare the estimated energy costs of generic roof systems (black vs. white vs. gray) over a ten year period. The  model takes into account the interior temperature to be maintained, the geographic location and the color (heat reflective properties) of the  roofing membranes (see "Assumptions" list). It should also be noted that a significant energy savings can be achieved with light colored roofing  membranes during the summer cooling period. Black colored membranes are estimated to provide a 1% benefit in reducing winter heating costs.  Membrane color becomes less significant as the R-value of the roof  insulation is increased as the examples indicate.