Vdd-programmable FPGAs have been proposed recently to reduce FPGA power, where Vdd levels can be customized for different circuit elements and unused circuit elements can be power-gated. In this paper, we first develop an accurate FPGA power model and then design novel Vddprogrammable interconnect switches with minimum number of configuration SRAM cells. Applying our power model to placed and routed benchmark circuits, we evaluate Vddprogrammable FPGA architecture using the new switches. The best architecture in our study uses Vdd-programmable logic blocks and Vdd-gateable interconnects. Compared to the baseline architecture similar to the leading commercial architecture, the best architecture reduces the minimal energy-delay product by 44.14% with 48% area overhead and 3% SRAM cell increase. Our evaluation results also show that LUT size 4 always gives the lowest energy consumption while LUT size 7 always leads to the highest performance for all evaluated architectures. Categories...