Are heat pump hot water systems noisy?

How loud is it, really?

A heat pump hot water system has a fan and a compressor in an outdoor box, so it sounds much like the outdoor unit of a split system air conditioner — a low hum with some fan noise, running in bursts rather than constantly. Published figures commonly land between about 37 and 50 dBmeasured near the unit. At the quiet end, Sanden's specifications state an operating noise level of 37 dB measured 1 metre from the heat pump unit.

Two cautions about that number. First, budget units generally sit at the louder end, so the spread across models is real — ask for the specification sheet figure in writing rather than accepting “whisper quiet” as a description. Second, a figure measured one metre away in a test setting is a best case. The same unit wedged into a narrow side passage between two brick walls will sound considerably worse, because hard surfaces reflect the sound instead of letting it disperse.

The rules that name this equipment

This is the part that surprises people. Heat pump water heaters are not covered by vague general nuisance law in the two biggest states — they get their own provisions, and the test is audibility next door, not a decibel limit you can measure your way out of.

Hours shown are the windows in which the equipment may be run. New South Wales: Protection of the Environment Operations (Noise Control) Regulation 2017, clause 53 — a clause written specifically for heat pump water heaters. Victoria: Environment Protection Regulations 2021, regulation 114 — hot water systems and heat pumps are listed residential equipment.

In NSW, clause 53 of the Protection of the Environment Operations (Noise Control) Regulation 2017 is titled Use of heat pump water heaters — a whole clause for this one product. It applies where the noise can be heard within any room of another home (excluding places like a garage, bathroom or laundry), whether or not a door or window to that room is open. Worth knowing: it is structured as warning-first. An authorised officer must warn you, and the offence arises only if it happens again within 28 days. You may see blogs quoting instant on-the-spot fines for this — that is not what the clause itself says.

In Victoria, the Environment Protection Regulations 2021 list hot water systems and heat pumps as residential equipment with set prohibited times. Noise is unreasonable if it happens in those hours and someone in a habitable room of another residence can hear it.

Other states and territories handle this through their own environment protection and local council rules rather than an identically worded clause, so check with your council if you are outside NSW or Victoria. The practical design goal is the same everywhere: it should not be audible in a neighbour's bedroom at night.

The overnight trap

Here is the mistake we see most often. People replacing an old electric storage tank carry over the off-peak habit and set the heat pump to run overnight — and overnight is exactly the window those rules restrict.

It is also the wrong setting for two other reasons. The air is at its coldest overnight, which is when a heat pump has to work hardest for each litre it heats. And if you have rooftop solar, overnight is the most expensive power you will buy all day. Running the unit in the middle of the day instead is usually better on all three counts at once — quieter hours, warmer air, cheaper (or free) electricity. Our running costs guide covers the bill side of that timing decision.

Placement: what actually makes the difference

• Bedroom windows, both sides of the fence. Map your own and your neighbour's before choosing the spot. This is the single decision that causes or avoids a dispute.
• Avoid narrow passages and internal corners. Hard parallel surfaces reflect and concentrate sound. An open spot with airflow is quieter than a tight one, for the same unit.
• Give it the clearance its manual requires. A heat pump needs to pull air across the evaporator. Boxing it in or crowding it against a fence restricts that airflow, which hurts efficiency as well as noise.
• Watch what it is mounted on. Vibration transmitted through a timber deck, a light wall or a shared structure carries further than airborne noise. Anti-vibration feet and a solid base are cheap insurance.
• Think about the pipe run. Moving the unit further from the bathroom for noise reasons means a longer run to the tap. There is a trade-off, and your installer should raise it.

What to ask before you sign

Get three things in writing on the quote: the model's published dB figure and the distance it is measured at, the exact positionthe unit will be installed in, and whether that position meets the manufacturer's clearance requirements. An installer who will not commit to the position on paper is one who may pick the easiest spot on the day rather than the best one.

If noise is a genuine constraint for you — a small block, a bedroom window close to the only available wall, a sensitive neighbour — say so at quote stage. It can steer you toward a quieter model, and the price difference is far smaller than the cost of moving a system after it is installed. Our is it worth it guide covers the cases where a heat pump is the wrong call altogether, including homes with no sensible outdoor position at all.

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