FPGA board's power consumption?

Idea 1: Use a PCI-E riser cable on which you will cut the power lanes and put a multimeter in.

Idea 2: Measure your computer power consumption in a specific scenario with a Kill-A-Watt. Power it down, install the FPGA board, and measure the power consumption again in the same conditions. The difference should be approximately your FPGA card power consumption.