State electric tanks have two thermostats — upper (with ECO safety) and lower. They sense tank temperature and control the heating elements.
Upper thermostat
Sits behind the upper access panel. Integrates the ECO (Energy Cut-Off) safety with the red reset button. Controls the upper heating element.
Lower thermostat
Behind the lower access panel. Simpler than upper (no ECO). Controls the lower heating element.
Symptoms of thermostat failure
- No hot water (upper thermostat stuck open or ECO tripped repeatedly)
- Water too hot — boiling or scalding (thermostat stuck closed; element runs continuously)
- Lukewarm water only (lower thermostat stuck open; only upper element fires)
- Heating element burned out shortly after replacement (thermostat caused over-firing)
Testing with a multimeter
- Turn off breaker
- Remove access panel
- Disconnect thermostat wires (note positions)
- Test continuity across the thermostat terminals — should change as you heat/cool the bimetallic sensing surface
- Permanently open or permanently closed = failed
Replacement
- Turn off breaker
- Remove access panel
- Note wire positions
- Disconnect wires
- Slide the failed thermostat out of its bracket (some have a small spring clip retainer)
- Insert new thermostat into bracket
- Connect wires per the notes
- Set temperature to 120°F (or "C")
- Replace access panel
- Restore breaker
ECO reset on upper thermostat
Press the red button firmly. If you can\'t feel/hear a click, the ECO wasn\'t tripped — the issue is elsewhere. If it clicks and the unit works briefly then trips again, the underlying cause (stuck thermostat, short, etc.) is still active.
Setting both thermostats to the same temperature
Critical: upper and lower thermostats must be set to the same temperature. Mismatched settings cause unpredictable performance and short element life.
Cost
- Upper thermostat with ECO: $30-50 OEM
- Lower thermostat (simpler): $25-40 OEM
- Pro replacement: $150-250
Bottom line
Test before replacing. Match wires when reconnecting. Set both thermostats to the same temperature. $30 part + 30 minutes = repair.