LED vs T5 reef lighting: which costs less to run?
Electricity is the smaller part of the T5 bill. In the example below, a 4-bulb 36-inch T5 fixture costs about $15.82 a month, and more than half of that is replacement bulbs. Two LED pucks cost about $5.17. The LEDs cost $174 more up front and pay that back in about 16 months. Every value is editable, and your inputs stay on this device.
LED vs T5 cost calculator
T5 fixture
LED
| Per month | T5 | LED |
|---|---|---|
| Energy | ||
| Electricity | ||
| Bulb replacement | $0.00 | |
| Total |
LED saves .
Formulas: kWh/month = watts × hours/day × 30.44 ÷ 1000. Bulb cost per month = bulbs × price per bulb ÷ months between changes. Payback months = (LED price − T5 fixture price) ÷ monthly saving. This uses rated bulb watts; T5 ballasts and cooling fans add some draw on top, which a plug-in energy meter will show. LED wattage is the full-power maximum, and most reef LEDs run below it, so the real LED bill is usually lower. LED lifespan isn't counted as a monthly cost here.
Where the examples come from: 18¢/kWh is close to the US average residential price of 18.31¢ for July 2026 (Colorado: 17.00¢), from the EIA Electric Power Monthly, Table 5.6.A. ATI says its 36-inch T5 bulbs are 39 W, so a 4-bulb fixture is 156 W, and recommends replacing T5 bulbs every 9–12 months, or 6–8 months if dimmed (ATI FAQ). BRS suggests every 12 months at 6–8 hours a day and every 9–12 months at 8–12 hours (BRS), so we use 12 months at 8 hours. The ATI 39 W 36-inch Blue Plus bulb was $26.95 at Bulk Reef Supply on October 17, 2026. $461.95 is BRS's regular price for the ATI 36-inch SunPower 4 × 39 W fixture, shown on its open-box listing (open box: $323.95) on the same date (BRS). For the LED side, the AquaIllumination Prime 16HD lists 59 W at full power and a 24 × 24 inch spread (AI), and was $317.99 at the AI store on October 17, 2026. Two pucks cover the length of a 36-inch tank, which is our assumption; mounts aren't included. Prices change, so enter what you pay.
What this does and doesn't tell you
- It compares cost, not light. T5s and LEDs spread light differently, and PAR depends on the fixture, height and settings. Pick the lighting your corals need first, then use this to compare the running cost of the options.
- Bulbs are T5's real running cost. At these prices a full set of four bulbs is $107.80 a year, which is more than the T5's whole electricity bill.
- Stretching bulb life changes the answer. Try 18 months between changes, the top of BRS's range for supplemental use, to see how a hybrid setup compares.
- Dimming LEDs saves more. If you run LEDs at 60% intensity, enter 60% of their wattage.
- Used fixtures change the payback. If you already own a T5 fixture, set its price to $0 and the LED's whole price becomes the extra cost to pay back.