Methods and apparatuses for circuit design to reduce power usage, such as reducing temperature dependent power usage, and/or to improve timing, such as reducing temperature dependent delay or transition time. At least one embodiment of the present invention reduces the power dissipation and improves the timing of an integrated circuit to optimize the design. A thermal analysis is used to determine the temperature dependent power dissipation of a circuit and the temperature distribution of the circuit resulting from dissipating the heat created by the temperature dependent power dissipation. Then, the components of the design are selectively transformed to reduce the power dissipation and to improve timing based on the temperature solution. The transformation may include placement changes and netlist changes, such as the change of transistor threshold voltages for cells or for blocks of the circuit chip.