For the LCLS-II X-ray instruments, we are developing laser power meters as compact X-ray power diagnostics to operate at soft and tender X-ray photon energies. These diagnostics can be installed at various locations along an X-ray FEL beamline in order to monitor the transmission of X-ray optics along the beam path. In addition, the power meters will be used to determine the absolute X-ray power at the endstations. Here we evaluate thermopile power meters, which measure average power, and have been chosen primarily for their compatibility with the high repetition rates at LCLS-II. A number of characteristics in the soft x-ray range are presented including the linearity, calibrations conducted with a photodiode and a gas monitor detector as well as ultra-high vacuum compatibility tests using residual gas analysis. The application of these power meters for LCLS-II and other X-ray FEL sources is discussed. Show Partial Abstract