No hot water? What it usually means — and what the fix costs
Lost your hot water, or it's only lukewarm or rusty? Here's how a plumber reads the symptom, the most likely faults behind it, and the typical repair-or-replace cost.
SureQuote editorial · reviewed June 2026 1 min readIf you have no hot water at all on an electric storage system, the most likely cause is a failed heating element, with a failed thermostat the next most likely. Both are serviceable parts (AS/NZS 3000), so the usual fix is a hot-water repair rather than a new unit.
If instead the water is rusty, the sacrificial anode has likely depleted and the cylinder is corroding (AS/NZS 3500.4); if the tank is leaking, the cylinder may have corroded through — which means a full replacement.
Repair or replace?
Most hot-water faults are repairs, not replacements. A failed element, thermostat or relief (TPR) valve, a depleted anode, or sediment build-up are all serviceable — a plumber resolves them with a hot-water repair, typically the cheapest path back to hot water.
The exception is a corroded, perforated cylinder. That is the end of the unit's life (AS/NZS 3500.4) and cannot be repaired — it resolves to a full hot-water system replacement, which is also the moment to consider upgrading to a more efficient heat-pump unit.
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