Replacing a hot water system: getting it done right, not just fast

What replacing a system involves

The simplest job is a like-for-like swap: a failed electric or gas storage tank comes out and a new one goes in the same spot, with the old unit taken away. Continuous-flow gas — the wall-mounted units that heat on demand — sits a little higher and may need minor pipe and valve changes. Heat pumps and solar cost more up front but slash running costs, and that's where the long-term savings live.

Changing system type, rather than swapping like for like, is where the price climbs. Moving from a tank to a heat pump, or from electric to gas, can mean new pipework, a gas line, new electrical circuits, or relocating the unit entirely. If you're switching, expect the quote to reflect that extra work.

Rebates are worth understanding before you buy. Federal certificates and various state schemes can take a meaningful chunk off heat pump and solar systems, so the headline price and the after-rebate price can be quite different numbers.

How the cost works

The band on this page spans from a straightforward tank replacement at the low end to a solar or heat pump upgrade at the top, before any rebates. The estimate here adjusts for the system type and household size, but the single most useful question you can ask every quoter is for the price after rebates — that's the number you'll actually pay.

Urgency has a cost too. A same-day emergency replacement limits your ability to compare, and that convenience usually carries a premium. If your tank is on its last legs but still limping, planning the replacement rather than waiting for the failure gives you room to choose well.

Verifying your installer

This is licensed work, no exceptions. Hot water installation must be done by a licensed plumber, and any gas unit also requires a licensed gasfitter — the two tickets often sit with the same person, but both need to apply to your job. Ask for the licence and check it against your state's register; any professional expects the question.

Beyond the licence, a good installer will talk about tank sizing for your household, whether your existing pipework and circuits suit the new unit, and — for heat pump and solar — the rebate paperwork, which they often handle for you. If your tank is over eight years old and leaking, the honest advice is usually to replace rather than repair, because tanks rarely come back from a leak.

Mistakes to avoid

Because these decisions often happen under pressure, the common mistakes are ones a little forethought prevents.

• Letting an emergency force a rushed choice — plan the replacement before the tank fails if you can
• Not confirming the plumber's licence, and the gasfitter's licence on a gas unit
• Comparing quotes on the headline price rather than the price after rebates
• Assuming a system-type change costs the same as a like-for-like swap
• Sizing the tank to the current household rather than the one you'll have in five years
• Repairing a leaking tank over eight years old instead of replacing it