This paper addresses the problem of calculation of building space sensible cooling or heating load from sensible heat gain or loss in an efficient manner on a digital computer. Two widely used methods are considered, referred to as the heat balance method and the ASHRAE weighting factor method. It is shown that by careful selection of a solution algorithm for the heat balance equations, the former method can be made much more efficient than suggested by early computer codes which used it. Moreover, it is shown that over-all computation times for this method thereby achieved are, for many important cases, no more than 10-15% greater than using the weighting factor approach. Since there is a loss of flexibility and accuracy with weighting factors, the heat balance may be the preferred approach in future energy analysis computer programs.