Reptile heat lamp vs. under-tank heater: running cost
An under-tank heater is cheaper to run: about $22 a year versus $79 for a reptile heat lamp at typical use and 17.99¢/kWh, a $57 difference.
| Reptile heat lamp | Under-tank heater | |
|---|---|---|
| Typical watts | 100 W | 20 W |
| Watt range | 40–250 W | 8–45 W |
| Typical use | 12 hours a day | 24 hours a day |
| Energy per year | 438 kWh | 123 kWh |
| Cost per hour | 1.8¢ | 0.3¢ |
| Cost per day | 22¢ | 6.0¢ |
| Cost per month | $6.57 | $1.84 |
| Cost per year | $79 | $22 |
| Per year in Hawaii (43.51¢) | $191 | $53 |
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What drives the difference
- Reptile heat lamp: Basking bulbs draw their rated watts the whole time they're on; a 100 W lamp 12 hours a day uses about 440 kWh a year.
- Under-tank heater: Heat mats draw 8-40 W continuously, usually on a thermostat.
Ways to cut either cost
Cycles the mat off when the target temperature is reached.
See options on AmazonDims the lamp when the basking spot is warm enough.
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Frequently asked questions
Which costs more to run, a reptile heat lamp or an under-tank heater?
At typical use and the U.S. average rate (17.99¢/kWh), a reptile heat lamp costs about $79 a year versus $22 for an under-tank heater. That's $57 more, or 3.6× as much.
How many watts do reptile heat lamp and under-tank heater use?
A reptile heat lamp typically draws 100 W (range 40–250 W). An under-tank heater draws 20 W (range 8–45 W). Watts alone don't decide cost. Hours of use, cycling and standby matter just as much.
Rates: EIA, 12 months ending 2026-07. Methodology.