What does a grow light cost to run?

Run the numbers on your own use

Change any of these and the figures update. The defaults are the typical case described above; your rate is the input that moves the answer most.

Why this is lower than the number you will see elsewhere

Almost every published answer to this question multiplies the rating on the label by the hours the appliance is switched on. For a grow light that gives 1,752 kWh a year, or $321.

Constant while on, and the on period is long by design.

The arithmetic, step by step

Nothing here is hidden, so you can check it or change it. Working in the order the formula runs:

1. 300 W — what it draws while it is actually drawing. This is the rating on the plate.
2. × 100% — the share of its in-service time it is really pulling that. Constant while on, and the on period is long by design.
   That gives 300 W averaged across the hours it is on.
3. × 16 hours a day × 365 days — One 300 W LED fixture on an 16-hour photoperiod.
   300 × 16 × 365 ÷ 1,000 = 1,752 kWh a year.
4. + standby — 1 W for the other 8.0 hours a day, which is 2.9 kWh a year. People leave this out and it is not always small.
5. × 18.34¢ — the US average residential rate for June 2026.
   1,755 kWh × 18.34¢ = $322 a year.

Change any assumption in the calculator above and every figure on this page moves with it. The two that matter most are your rate, which varies 4× across the country, and the hours — the duty cycle is a property of the appliance, but the hours are a property of you.

How sensitive is that number?

A single figure invites more confidence than it deserves. Here is the same appliance under assumptions either side of the default, so you can see how much of the answer is the appliance and how much is the guess about how you use it.

Everything else held at the default. The spread here is the honest error bar on the headline figure.

What it costs per hour, day and month

At 18.34¢ per kWh, the US residential average for June 2026.

The thing worth knowing

Sixteen hours a day for a year is 5,840 hours, so a grow light is one of the highest-duty loads in a house. Marketing wattage is often the ‘HID equivalent' rather than the actual draw, so check the fixture’s rated power, not the headline number.

What it costs in your state

The appliance is the same everywhere; the rate is not. Running this grow light costs $925 a year in Hawaii and $230 in Nevada — a difference of 4×.

Cost of running one grow light for a year, by state. Residential average price, EIA June 2026.

Other lighting costs

• Incandescent bulb

  $20 a year

  One 60 W bulb, five hours a day.

• LED light bulb

  $3.01 a year

  One 60 W-equivalent bulb, five hours a day.

Questions

Source: U.S. Energy Information Administration, Electric Power Monthly, Table 5.6.A, June 2026. U.S. Government work, public domain.

How every figure on this page is computed · Where the data comes from