If Australian households switched their hot water heaters to run off daytime solar power, it could lead to significant reductions in carbon emissions and lower energy bills, while maximising the benefits of cheap, abundant solar energy. Hot water heating is responsible for 15-30% of a home’s total energy consumption, second only to heating and cooling systems. A large proportion of Australian households use electric water heaters with storage tanks, which act like thermal batteries, storing more energy than many home battery systems. Traditionally, these heaters have operated during off-peak hours overnight, but shifting them to run during the day could help soak up excess solar energy, reducing waste and better matching supply and demand.