Heat-pump hot water pairs neatly with rooftop solar when the tank heats in sunny hours. Poor timers leave an efficient heater quietly importing evening power while panels export for pennies.
Why timing dominates brand talk
A heat pump already uses far less energy than a resistive element. Shifting its remaining kilowatt-hours into solar hours multiplies bill benefit. Legacy controlled-load schedules designed for cheap overnight coal power may fight your solar profile.
- Ask the plumber and electrician to coordinate timer or PV diverter settings
- Size the tank so midday reheats cover evening showers
- Watch winter: shorter days may need a shoulder-hour top-up
- Insulate pipe runs to keep gained heat
Hot water is a daily battery you already own — charge it with the roof.
PV diverters versus smart timers
Diverters send surplus to an element or signal a heat pump; timers approximate solar hours. Diversion is neater when surplus varies; timers are simpler when patterns are stable.
Export caps raise the stakes
On export-limited sites, soaking surplus into the tank is often higher value than clipping generation.
Commissioning habit
After install, check a week of monitoring to confirm the heater runs when the array is alive. Adjust seasonally.