Side-by-side comparison
QuestionDedicated PV resistancePV + heat-pump water heaterSolar thermal
Energy pathPV → resistance heat → tankPV/grid → heat pump → tankSun → collector fluid → heat exchanger → tank
Main appealSimple thermal load; dedicated generation; storage in waterHigh electrical efficiency; flexible PV use; mature productsDirect collection of solar heat; strong output in suitable climates
Main tradeoffResistance heat uses more PV electricity than a heat pump for the same delivered heatEquipment, air-space, noise, condensate, and cold-climate performance matterRoof plumbing, freeze/overheat control, pumps or thermosiphon design, and maintenance
Backup strategyMust be designed explicitlyTypically built into or paired with the applianceTypically paired with electric or fuel backup
Best evaluation questionIs a dedicated off-grid or curtailed-PV thermal load valuable here?Can site conditions support efficient heat-pump operation?Does climate and hot-water demand justify a thermal collector loop?
What does current guidance favor?
For many grid-connected homes, a high-efficiency heat-pump water heater is a strong baseline because it moves ambient heat rather than creating all heat by resistance. Dedicated PV resistance becomes more interesting when simplicity, DC coupling, off-grid operation, otherwise-curtailed generation, or large low-cost thermal storage materially changes the project economics.