This paper presents the first detailed long-term stock turnover mod­el to inves­ti­gate sce­nar­ios to decar­bonize the res­i­den­tial water heat­ing sec­tor in Cal­i­for­nia, which is cur­rent­ly dom­i­nat­ed by nat­ur­al gas. We mod­el a mix of water heat­ing (WH) tech­nolo­gies includ­ing con­ven­tion­al and on-demand (tank-less) nat­ur­al gas heat­ing, elec­tric resis­tance, exist­ing elec­tric heat pumps, advanced heat pumps with low glob­al warm­ing refrig­er­ants and solar ther­mal water heaters. Tech­ni­cal­ly fea­si­ble pol­i­cy sce­nar­ios are devel­oped by con­sid­er­ing com­bi­na­tions of WH tech­nolo­gies with effi­cien­cy gains with­in each tech­nol­o­gy, low­er­ing glob­al warm­ing poten­tial of refrig­er­ants and decreas­ing grid car­bon inten­si­ty. We then eval­u­ate ener­gy demand, emis­sions and equip­ment replace­ment costs of the path­ways. We devel­op mul­ti­ple sce­nar­ios by which the annu­al green­house gas emis­sions from res­i­den­tial water heaters in Cal­i­for­nia can be reduced by over 80% from 1990 lev­els result­ing in an annu­al sav­ings of over 10 Mil­lion Met­ric Tons by 2050. The over­all cost of tran­si­tion will depend on future cost reduc­tions in heat pump and solar ther­mal water heat­ing equip­ment, ener­gy costs, and hot water consumption.