Hot Water System Installation Cost: What Drives the Price

Hot water system installation cost comes down to two things: what you're putting in, and how much has to change to put it there. A straight swap of the same type and size, in the same spot, is the simplest job there is. Change the fuel, the location or the size, and the price moves with it.

You won't find a figure in this post, because we don't publish a price list (the reasons are on our how we price page). What you will find is what we look at when we quote, so you can work out which kind of job you've got before you ring anyone.

Start with the question that matters most: like-for-like or a change?

Almost every hot water quote falls into one of two groups.

A like-for-like replacement means the same fuel, roughly the same size, in the same place. Gas storage for gas storage, electric for electric, continuous flow for continuous flow. The water, gas or power connections are already there and already sized for it, so the job is mostly taking the old unit out, putting the new one in, and commissioning it.

A change is anything else. Electric to heat pump. Gas storage to continuous flow. Moving the unit from the laundry to outside. Going up a size because the household has grown. Each of those can bring extra work that a straight swap doesn't have.

Is it cheaper to replace like-for-like?

Usually, yes, on the day. The connections are in place and there are fewer surprises.

That doesn't make it the right answer for every house. If your electric tank runs out every evening, replacing it with the same tank buys you another ten years of running out. If you're planning to go all-electric, putting a new gas storage unit in now can be money you spend twice. It's worth thinking about what you want the next system to do before you decide the cheapest install is the best value.

What the new unit is

The system itself is a big part of the price, and the range between types is wide.

System type	What usually affects the install
Electric storage	Simplest to swap. Size and whether it sits on the off-peak circuit.
Gas storage	Flue clearances, gas supply, and whether it's indoor or outdoor.
Gas continuous flow	Needs a gas line big enough for the burner, which older pipework often isn't.
Heat pump	Needs outdoor space with airflow, a suitable power circuit, and thought about noise near a neighbour's window.
Solar	Roof work, collectors and a booster. Usually the most involved install.

Within each type, size matters. A larger tank or higher-output continuous flow unit costs more to buy, and sometimes needs a bigger gas or power supply to run.

Brand and warranty matter too. There's a real difference between an entry-level tank and a premium one with a longer tank warranty. Where there's a genuine choice, we'll price both and let you pick.

Access: where the old unit lives

Access is often a bigger share of the hot water system installation cost than people expect, and it's the part a phone quote can't always see.

An outdoor tank on a flat path beside the garage is easy. The same tank in a roof space, up a flight of stairs, in a cupboard with a door that's narrower than the new unit, or at the end of a side passage with a step and a gate, takes longer and sometimes needs a second person.

This comes up a lot in the Hills District. Plenty of 1970s and 80s homes in Castle Hill and Baulkham Hills have the hot water unit tucked into an internal cupboard or under the house, and the newer estates around Kellyville and The Ponds often have units squeezed into narrow side setbacks.

If you can send a photo of where the unit sits and the path to it, we can usually tell you on the phone whether access is going to be a factor.

How much to replace a hot water system when you're switching fuel

Changing fuel type is where the bigger differences in hot water system cost come from, because you're changing the connections, not just the unit.

Does changing from gas to heat pump cost more to install?

Generally, yes. A heat pump needs a suitable electrical circuit, and a licensed electrician may need to run one or upgrade what's there. The old gas line has to be safely capped off by a licensed gasfitter. The heat pump also needs a spot outside with enough airflow, which isn't always where the old gas unit was.

Against that, there are NSW government incentives for heat pump installs that can offset part of the price. The eligibility rules change, so we've kept the detail in a separate post on the heat pump hot water rebate in NSW.

Electric to gas, or storage to continuous flow

Going from electric to gas needs a gas supply to the unit's location, and possibly a new flue if it's indoors. Going from gas storage to gas continuous flow often needs a larger gas line, because a continuous flow burner draws far more gas at once than a storage tank. Older homes on the Upper North Shore sometimes have gas pipework that was sized decades ago for a stove and a small heater, and it simply can't feed a modern continuous flow unit without an upgrade.

Electric continuous flow units draw a lot of current, and many homes need a switchboard or supply upgrade to run one. That's an electrician's job, and it's worth knowing about before you settle on the unit.

The parts people don't think about

A few items appear on most installation quotes and are easy to overlook when comparing.

• A tempering valve. New installs need hot water delivered to bathrooms at no more than 50°C, while the tank is held at 60°C to control legionella. A tempering valve does that blending. If your existing valve is old or there isn't one, a new one is part of a compliant install. Our post on what a tempering valve is explains why it matters.
• Isolation valves, pressure limiting valves where mains pressure is high, and new flexible connectors are commonly replaced at the same time rather than reused.
• Some units need a new slab, a safe tray for an indoor install, or wall brackets for continuous flow.
• The old unit has to be drained, carried out and taken away.
• Plumbing work in NSW is certified by the licensed plumber who does it, and gas work must be done by a licensed gasfitter who issues a compliance certificate. That paperwork is part of doing the job properly, not an extra.

If two quotes look far apart, check whether both include these items. Often the gap is a tempering valve, disposal or a gas line that one quote has left out.

Emergency or planned?

When a tank splits at 6am and floods the laundry, you need hot water back that day, and you take what can be sourced quickly. After-hours labour is charged at a higher rate than standard hours, and we'll tell you what that rate is before we're dispatched.

If your unit is getting old but still working, you have more options. You can compare system types, look into incentives, and book the job in standard hours. Rusty water, a rumbling tank or a weeping relief valve on a unit past ten years are signs it's time to start planning. Our guide to how long hot water systems last covers the warning signs by system type.

Hot water system installation cost: which scenario are you in?

Here's a quick way to place yourself:

• Simplest: same fuel, same size, same spot, easy outdoor access.
• Moderate: same fuel but harder access, a size change, or a tempering valve and fittings to replace.
• Most involved: changing fuel type, moving the unit, or a gas or electrical upgrade to support the new system.

Knowing which group you're in gets you a much more useful answer on the phone.

What to tell us for a useful number quickly

• The make, model and size of your current unit (it's on the label on the side)
• Gas or electric, storage or continuous flow
• Where it sits and what the path to it is like
• What you want to replace it with, if you know
• Whether it's failed or still working

With those details, a straight hot water swap is one of the jobs we can often price very closely over the phone.

Getting a fixed price

There's no call-out fee and no charge to quote. We'll look at the job, tell you what's involved, and give you a fixed price before any work starts. That's the number on the invoice. If we find something unexpected, we stop and talk to you first.

If you're weighing up a replacement anywhere across the Hills District, Hornsby Shire or the Upper North Shore, give us a call and describe what you've got. Have a look at our hot water system installation and repairs page for the systems we fit and how the job runs.