Grow Light Electricity Cost Calculator
Estimate grow-light energy use and running cost from actual watts, daily hours, your electricity rate, and the number of fixtures.
Use your own tariff and the fixture’s actual wall draw. “1000 W equivalent” is not the power it consumes.
Choose your inputs and use the button above to get a result.
The cost formula
Energy in kWh = actual watts ÷ 1,000 × hours per day × days × number of identical fixtures. Cost = kWh × your price per kWh. A 30 W light on for 12 hours a day uses 10.8 kWh over 30 days. At 0.20 per kWh, that is 2.16 in the currency you choose.
The rate field is an example, not a current local tariff. Read your bill for the marginal energy rate and account for time-of-use prices if they apply. This calculation excludes standing charges, taxes that are not already in your rate, heating or cooling effects, and electricity used by other equipment. The currency selector changes only the label; it does not convert exchange rates.
Use enough light efficiently
A cheaper schedule is useful only if the plant receives enough light. Use the DLI and timer calculator with a measured or manufacturer-supplied PPFD at leaf height. Watts describe electrical input, not the amount of light a leaf receives.
Use a timer and measure the actual draw with a plug-in meter when available. Group plants with compatible needs, but leave air space and inspect both the brightest and dimmest positions. Read the worked grow-light cost guide for a practical comparison.
Frequently asked questions
Can I use the advertised equivalent wattage?
Use actual power draw in watts. Equivalent wattage is a marketing comparison and can greatly overstate electricity consumption.
Does selecting a currency change my electricity rate?
No. Enter your own local price per kWh. The selector only labels the result.