How much does a water heater thermostat replacement cost?

The two numbers

Fixr's repair guide prices the thermostat twice, and the difference is the whole decision:

Fixr's wording on the repair: a thermostat is a vital component of any water heater, as it helps monitor and control the temperature of the water, and broken thermostats can lead to water heaters overheating or failing to heat at all. On the replacement: thermostats break down for various reasons, including technical defects, old age and improper installation, and replacement thermostats are inexpensive and easy to fit.

Our conclusion, marked as ours: with $25 to $100 between the two, and with the part itself described as inexpensive, paying to repair a component that has already failed once rarely pays off. Fixr does not make this recommendation; it publishes both prices.

What a failing thermostat looks like

This Old House lists the symptoms without naming a price. Taken together with Fixr's table, they tell you which fault you are looking at.

• No hot water at all. This Old House: the absence of hot water could indicate a failed thermostat, heating element or gas control valve.
• Inconsistent water temperature. This Old House names this as a sign of a failing heating element or thermostat.
• Water far too hot. Fixr's overheating case, and the one to treat as urgent, because the pressure relief valve is then the only thing between the tank and dangerous pressure.

Rule out the cheap causes first

The same symptom has cheaper explanations, and This Old House puts them first: the pilot may not be lit, which is a relatively easy fix, and on electric models a tripped breaker or faulty heating element could be the cause.

Fixr's prices for those alternatives:

A blown fuse at $50 to $75 and a heating element at $200 to $750 produce the same complaint from the tap. Paying a professional to diagnose before authorising a part is worth it here.

Electric tanks have two of them

This Old House lists two heating elements, usually 4,500 watts each, as a key feature of an electric storage tank water heater. Our own note, not from either source: each of those heating elements is paired with its own thermostat, upper and lower. That matters for reading a quote: a plumber who finds one failed thermostat is often looking at one of two, and the second one is a few minutes of extra labour on a visit you are already paying for.

It also matters for the diagnosis. This Old House's flushing guide describes sediment at the bottom of the tank, where the heating element sits, and notes that calcified sediment traps heat and overworks the lower element. A lower thermostat that fails on a tank that has never been flushed is a symptom, not the disease. See water heater maintenance cost.

Gas units

A gas unit has a thermostat too, but it is built into the gas control valve, which is why Fixr prices that part separately at $150 to $300 for replacement. On a gas heater, "the thermostat has gone" and "the gas valve has gone" are frequently the same repair. See gas valve replacement cost.