How many heater watts per gallon for a turtle tank?

Rules of thumb range 2–5 W/gal depending on the temperature rise (ΔT) and lid coverage. This calculator uses a heat-loss model to compute more precise requirements.

Is it better to run one heater or two smaller heaters?

Two smaller heaters add redundancy. If one fails OFF, the remaining unit may still maintain a safe ΔT. The tool simulates this under "Dual-heater failure OFF".

How long will it take to reach my target water temperature?

Time-to-temp depends on tank volume, heater wattage, and losses. The tool estimates time using water thermal mass and net heating power.

How much will it cost to run my turtle heater?

Monthly kWh and cost are estimated using the duty cycle at your target temperature and your electricity rate.

Turtle Tank Heater Wattage & Temperature Rise Calculator

Temp Volume Dimensions

white theme · Bootstrap 5 · jQuery · Plotly

Tank Geometry

Length

Width

Water depth

Tank height (for glass area)

Displacement (decor/land) %

0%10%40%

Lid / Cover

Environment

Ambient day

Ambient night

Day hours

Airflow / Draft

Seasonal preset

Species preset

Suggested target

Target & Current

Current water

Target water

ΔT (auto)

Tip: Set Target water to species recommendation; use Current water from your thermometer.

Heater Plan

Configuration

Heater type

Thermostat hysteresis (°C)

Candidate wattages Hold Ctrl/Cmd to select multiple (for charts & comparisons).

Custom W

Power & Cost

Electricity rate

$/kWh

Currency

Advanced (click to expand)

Thermal & loss constants

Density ρ (kg/L)

Specific heat c (J/kg·°C)

Safety factor

Glass U (W/m²·°C)

h_conv (W/m²·°C)

h_evap base

Insulation reduction (%)

0%0%60%

Efficiency η override (0–1)

Charts

Time to reach target vs candidate wattages

Duty cycle at target vs ΔT

Monthly cost vs ambient (sensitivity)

Two-heater failure OFF: maintainable ΔT

Scenario Manager

Compare A

Compare B

Safety & Good Practices

Use a GFCI outlet and a drip loop on all cords.
Prefer two smaller heaters on medium/large tanks for redundancy.
Place heater near circulation and never operate a heater dry.
Use an independent thermometer to verify water temp; calibrate thermostats periodically.
Shield heaters/cords from turtle contact with guards or placement.

Recommended Configuration

Draft

Tank volume (net)—

ΔT target (water − ambient)—

Loss coefficient (UA)—

Heater plan—

Required watts (min / typical / robust)—

Recommended—

Time to target (approx)—

Duty cycle @ target—

Energy & cost (day)—

Energy & cost (month)—

Dual-heater failure OFF → maintainable ΔT—

Oversize risk (small tank)—