A self-powered variable transmittance optical device, such as a smart window or other device, and associated method are provided. The device comprises one or more transparent substrates, with a switching material disposed thereon or therebetween. The switching material may be a hybrid photochromic/electrochromic material capable of transitioning from a first transmittance state to a second transmittance state with application of electricity, and from second state to first state due to another stimulus, such as UV radiation. Electrodes are coupled to the switching material for applying electricity. An electrical system provides for controllable application of the electricity, and may store energy. Energy is provided by an energy-harvesting power source such as a solar cell or other photovoltaic source, or array thereof, or another device for harvesting vibrational or thermal energy. Energy harvesting, energy storage capacity and/or switching material may be configured to provide at least a predetermined level of device operability.