The invention provides methods and systems for water dissociation with microplasma generated in microchannel plasma arrays or chips. Preferred methods and systems introduce water vapor into a microchannel plasma array. Electrical power is applied to the microchannel plasma array to create a plasma chemical reaction of the water vapor in the microchannel plasma array. Dissociated hydrogen and/or oxygen gas is collected at an output of the microchannel plasma array. The water vapor can be entrained in a carrier gas, but is preferably introduced without carrier gas. Direct introduction of water vapor has been demonstrated to provide efficiencies at an above 60%. The use of carrier gas reduces efficiency, but still exceeds efficiencies of prior methods discussed in the background.