AO Smith is a well-known brand offering a range of residential water heaters, including electric, gas, and tankless models. Adjusting the thermostat to a safe and efficient temperature can improve comfort while reducing energy use. This article explains how to raise or lower the temperature on AO Smith water heaters, covers safety considerations, and provides troubleshooting tips to ensure reliable performance.

Identify Your AO Smith Water Heater Type

AO Smith manufactures several styles, and the adjustment process depends on the model. Common types include electric storage, gas storage, and tankless models. Electric storage units typically use a thermostat inside the access panel, while gas models use a dial located near the burner, and tankless systems rely on digital controls or service panels. Confirm the exact model number and consult the user manual before making changes.

Safety First: Before You Adjust Temperature

Adjusting water heater temperature carries scalding risk and potential energy inefficiency. Set a safe maximum around 120°F (49°C) to minimize burn risk, especially for children and elderly household members. If the water feels too hot or too cold, test several taps before changing the thermostat and ensure the power supply is off when opening access panels on electric units.

Electric Storage Water Heaters: How To Change The Temperature

Electric AO Smith storage models typically have two or more thermostats behind an access panel. Steps include:

Turn off the power at the breaker labeled for the water heater.
Open the access panel and remove insulation to expose the thermostat.
Use a non-contact thermometer to gauge water temperature for accuracy.
Turn the thermostat dial slowly, adjusting in small increments (usually 5–10 degrees).
Replace insulation and panel, then restore power at the breaker.
Test water at a tap after an hour to verify the temperature.

Note: If your unit has a separate upper and lower thermostat, adjust both gradually and in a balanced way to avoid overheating at the top or bottom of the tank.

Gas Storage Water Heaters: Temperature Adjustment

Gas models typically adjust via a thermostat dial near the valve assembly:

Turn off the gas supply or set the thermostat to a moderate setting.
Locate the thermostat dial and remove the access panel.
Use a flathead screwdriver to rotate the dial to the desired temperature. Increase or decrease in small increments.
Replace the cover and relight the pilot if necessary, following the manufacturer’s instructions.
Turn the gas back on and run hot water from a faucet to confirm the new temperature.

If your gas water heater has a control board or electronic display, follow the digital interface or user manual to adjust setpoints.

Tankless Water Heaters: Adjusting Temperature Settings

Tankless AO Smith heaters use digital controls to manage output temperature. Steps include:

Navigate to the main settings menu on the control panel.
Select “Temperature,” then adjust upward or downward in small increments.
Confirm changes and allow the unit to reheat to the new setpoint. Test water temperature at multiple taps.

Tankless units often have a recommended maximum output temperature around 120–140°F (49–60°C) depending on model and usage. Avoid exceeding the highest safe setting to prevent scalds and efficiency loss.

Common Issues After Adjusting Temperature

After changing the temperature, several issues may arise:

Inconsistent water temperature: May indicate mineral buildup, faulty thermostats, or circulation problems. Descale if mineral scale is present, especially in hard water areas.
Water too cold or not heating: Check power supply for electric models, ensure gas supply is uninterrupted for gas units, and verify control settings.
Noisy operation: Sediment or mineral buildup in the tank can cause rumbling; draining and flushing the tank can help.
Thermostat calibration drift: If temperatures vary widely, the thermostat may need replacement.

Maintenance That Supports Stable Temperatures

Regular maintenance helps maintain consistent temperatures and efficiency:

Schedule annual professional inspections for gas and electric units.
Flushing the tank annually to remove sediment for storage models.
For hard water regions, consider water conditioning or a descaler to protect heat exchangers.
Inspect the anode rod every 2–3 years to prevent tank corrosion and maintain heating efficiency.

Warranty, Safety, And Professional Help

AO Smith appliances carry warranties with conditions linked to proper use and maintenance. If a problem persists after adjusting temperature, contact an authorized technician. Do not bypass safety devices, and avoid making unauthorized modifications to thermostats or wiring, which can void warranties and create hazards.

Tips For Optimal Performance And Energy Efficiency

Maintain a steady setpoint around 120°F to balance comfort and safety.
Bundle hot water usage to reduce energy demand and prevent temperature fluctuations during high-demand periods.
Install a high-efficiency heat trap or insulation on older tanks to minimize heat loss.
Consider upgrading to a newer model with better insulation if the unit is old or frequently loses temperature.

Adjusting the temperature on an AO Smith water heater can improve comfort, safety, and energy efficiency when done correctly. By identifying the unit type, following model-specific steps, and performing routine maintenance, homeowners can achieve reliable hot water performance while minimizing energy waste.