Should my heat pump hot water run during the day or overnight?

Set the timer to the hours your panels produce most, usually from late morning to mid afternoon. The tank heats on your own power and in the warmest air, and it's full again by the evening showers. On short winter days the useful window shrinks, so allow a few more hours in June and July.

On a single-rate tariff, daytime still makes sense because the heat pump works more efficiently in warmer air. On a time-of-use tariff, compare your retailer's rates. The cheapest hours win, as long as they give the unit enough time to heat the tank.

If the tank is wired to a controlled load or off-peak circuit, the unit only gets power when the network switches that circuit on, usually overnight. Changing the timer on the unit won't change that. Moving to daytime heating may mean changing how the circuit is supplied, which is electrical work, while the tariff side is a question for your retailer.

A heat pump hums like a small air conditioner outdoor unit. Running it at 2am beside a bedroom window, yours or a neighbour's, is when people notice. On narrow blocks and in the newer estates around Point Cook, Tarneit and Werribee, the unit can end up close to a bedroom, which is another reason to favour daytime running.

Cold nights are the hardest hours for a heat pump. Laverton averages a July minimum of 5.2°C, frost can form on the coil, and the unit runs longer or leans on its backup element. After any power cut, check the clock and timer, as some units lose their settings.