You could also think of reversible blocks. For example, if you had an half-adder, you each constituent gate could be thought of as doing something like erasing in normal operation. If instead the half-adder was reversible, and you perform the operation, save the outputs, reverse it, and then erase the inputs, at least you only have to pay the Landauer tax on the input bits (rather than each intermediary bit). The bigger the block, the more you save.