---
title: "Grow Light Cost Calculator: Calculate Electricity Cost per Day and Month"
canonical: "https://theyieldgrid.com/grow-light-cost-calculator/"
model_id: "tyg-684"
model_version: "1.0.0"
last_reviewed: "2026-04-27T18:39:34"
reviewed_by: "Umer Hayiat"
---

# Grow Light Cost Calculator: Calculate Electricity Cost per Day and Month

> Canonical calculator: [https://theyieldgrid.com/grow-light-cost-calculator/](https://theyieldgrid.com/grow-light-cost-calculator/)

## What this calculator does

Home - Free Gardening Calculators & Tools - Grow Light Cost Calculator: Calculate Electricity Cost per Day and Month Electricity is one of the few input costs in a grow room that compounds invisibly. A 600-watt fixture running 18 hours a day looks affordable at roughly $1.51 per day, but that number becomes $45 per month and nearly $550 per year before a single harvest is complete. The error growers make is evaluating light purchases at the fixture level rather than the operational-cost level, which means the true cost of a lighting system never gets compared against yield targets or energy budgets.

## Inputs

| Input | ID | Type | Unit | Range or choices | Required |
|---|---|---|---|---|---|
| Grow Light Wattage | `indlc_watts` | number | watts | 1 to 50000 | No |
| Hours per Day | `indlc_hours` | number | Hours | 0.1 to 24 | No |
| Electricity Rate ($/kWh) | `indlc_rate` | number | $/kWh | 0.001 to 10 | No |

## Outputs

| Output ID | Default state |
|---|---|
| `indlc_watts_err` |  |
| `indlc_hours_err` |  |
| `indlc_rate_err` |  |
| `indlc_results_panel` | Your Grow Light Cost Estimate Daily Running Cost — $/day Per Day — Per Month (30 days) — Cost Breakdown — Relative Scale / Day — / Month — / Year — Warnings & Standards Reference: Common Grow Light Costs @ $0.14/kWh, 18 hrs/day Light Type Watts $/Day $/Month Small LED Panel 100 W $0.25 $7.56 Mid LED Grow 300 W $0.76 $22.68 How this calculator works Formula: Cost = (Watts ÷ 1000) × Hours/Day × Rate ($/kWh) Step 1 — Convert watts to kilowatts: kW = Watts ÷ 1000 e.g. 600 W ÷ 1000 = 0.6 kW Step 2 — |
| `indlc_out_primary` | — |
| `indlc_out_day` | — |
| `indlc_out_month` | — |
| `indlc_out_warnings` | Warnings & Standards |
| `indlc_warnings_list` |  |

## Formula and method

This 3D breakdown illustrates how wattage converts into kilowatt-hours and compounds over a standard 30-day billing cycle. Show the calculation steps The formula is: Cost = (Watts / 1000) × Hours/Day × Rate ($/kWh) Step 1 – Convert watts to kilowatts: Electricity billing uses kilowatts, not watts. Divide the wattage by 1,000. A 600-watt fixture becomes 0.6 kW. Step 2 – Calculate daily energy consumption: Multiply kilowatts by the number of hours the fixture runs. 0.6 kW × 18 hours = 10.8 kWh per day. Step 3 – Calculate daily cost: Multiply kWh/day by your electricity rate. 10.8 kWh × $0.14 = $1.512 per day. Results are displayed to four decimal places for precision at low wattages. Step 4 – Calculate monthly cost: Daily cost × 30 days = monthly cost. This is a flat 30-day month, not a calendar-month average. Rounding: Daily costs display to four decimal places. Monthly costs display to two decimal places (nearest cent). The intermediate kWh value is not rounded, preserving accuracy through each step. Unit conversions used: 1 kW = 1,000 W. No temperature, pressure, or flow conversions are involved. Assumptions and Limits The calculation assumes continuous, uninterrupted operation at the stated wattage for the full duration of the photoperiod. Dimming, duty cycling, or variable-output fixtures will draw less than their rated wattage and must have their actual draw measured at the wall. HID, HPS, and CMH fixtures include a ballast that consumes additional power beyond the bulb's rated wattage. This tool does not automatically add a ballast overhead. Enter the total system draw, not just the bulb wattage. The monthly cost figure uses a fixed 30-day month. Actual utility billing cycles vary and may span 28 to 33 days depending on the provider. The rate field accepts a single flat rate. Tiered utility pricing, time-of-use rates, and demand charges are not modeled. Growers on tiered plans may pay a higher marginal rate once a baseline threshold is crossed. Heat generated by grow lights adds to the cooling load of the space. The electricity cost of running HVAC to offset that heat is entirely separate and is not included in this calculation. For a sizing reference, see the grow room AC sizing guide . Wattage must be between 1 W and 50,000 W. Hours must fall between 0.1 and 24. Rate must be between $0.001 and $10.00/kWh. Inputs outside these ranges will return a validation error rather than a result. This tool calculates operating electricity cost only. It does not include fixture purchase price, bulb replacement intervals, driver or ballast replacement, or depreciation, all of which factor into total cost of ownership.

## Verified worked examples

### Example 1: Small Home LED Grow Panel

Wattage: 200 W Hours per day: 16 Electricity rate: $0.14/kWh kW = 200 / 1000 = 0.2 kW kWh/day = 0.2 × 16 = 3.2 kWh Cost/day = 3.2 × $0.14 = $0.448 Result: $0.45/day, $13.44/month, $163.52/year A small LED panel running a standard vegetative photoperiod costs less than $14 per month. At this scale, electricity is not the dominant expense, but the calculation becomes critical when scaling to multiple fixtures in the same room.

### Example 2: Standard 600-Watt HPS Flowering Setup

Wattage: 600 W Hours per day: 18 Electricity rate: $0.14/kWh kW = 600 / 1000 = 0.6 kW kWh/day = 0.6 × 18 = 10.8 kWh Cost/day = 10.8 × $0.14 = $1.512 Result: $1.51/day, $45.36/month, $551.88/year The 600-watt HPS remains a benchmark fixture in small-scale production. At $45 per month for lighting alone, a grower modeling a complete grow room must add HVAC, fans, pumps, and other equipment costs on top of this figure to get an accurate operational picture.

### Example 3: Commercial LED Bar at Higher Utility Rate

Wattage: 1,000 W Hours per day: 20 Electricity rate: $0.18/kWh (higher-cost utility region) kW = 1000 / 1000 = 1.0 kW kWh/day = 1.0 × 20 = 20.0 kWh Cost/day = 20.0 × $0.18 = $3.60 Result: $3.60/day, $108.00/month, $1,314.00/year When a rate of $0.18/kWh replaces the national average, monthly costs for a single 1,000-watt fixture cross $100. This triggers the calculator's built-in warning, and it is precisely the threshold where evaluating an LED system with higher initial cost but lower wattage becomes financially justified.

## Assumptions

Wattage: 600 W Hours per day: 18 Electricity rate: $0.14/kWh kW = 600 / 1000 = 0.6 kW kWh/day = 0.6 × 18 = 10.8 kWh Cost/day = 10.8 × $0.14 = $1.512 Result: $1.51/day, $45.36/month, $551.88/year The 600-watt HPS remains a benchmark fixture in small-scale production. At $45 per month for lighting alone, a grower modeling a complete grow room must add HVAC, fans, pumps, and other equipment costs on top of this figure to get an accurate operational picture. This 3D breakdown illustrates how wattage converts into kilowatt-hours and compounds over a standard 30-day billing cycle. Show the calculation steps The formula is: Cost = (Watts / 1000) × Hours/Day × Rate ($/kWh) Step 1 – Convert watts to kilowatts: Electricity billing uses kilowatts, not watts. Divide the wattage by 1,000. A 600-watt fixture becomes 0.6 kW. Step 2 – Calculate daily energy consumption: Multiply kilowatts by the number of hours the fixture runs. 0.6 kW × 18 hours = 10.8 kWh per day. Step 3 – Calculate daily cost: Multiply kWh/day by your electricity rate. 10.8 kWh × $0.14 = $1.512 per day. Results are displayed to four decimal places for precision at low wattages. Step 4 – Calculate monthly cost: Daily cost × 30 days = monthly cost. This is a flat 30-day month, not a calendar-month average. Rounding: Daily costs display to four decimal places. Monthly costs display to two decimal places (nearest cent). The intermediate kWh value is not rounded, preserving accuracy through each step. Unit conversions used: 1 kW = 1,000 W. No temperature, pressure, or flow conversions are involved. Assumptions and Limits The calculation assumes continuous, uninterrupted operation at the stated wattage for the full duration of the photoperiod. Dimming, duty cycling, or variable-output fixtures will draw less than their rated wattage and must have their actual draw measured at the wall. HID, HPS, and CMH fixtures include a ballast that consumes additional power beyond the bulb's rated wattage. This tool does not automatically add a ballast overhead. Enter the total system draw, not just the bulb wattage. The monthly cost figure uses a fixed 30-day month. Actual utility billing cycles vary and may span 28 to 33 days depending on the provider. The rate field accepts a single flat rate. Tiered utility pricing, time-of-use rates, and demand charges are not modeled. Growers on tiered plans may pay a higher marginal rate once a baseline threshold is crossed. Heat generated by grow lights adds to the cooling load of the space. The electricity cost of running HVAC to offset that heat is entirely separate and is not included in this calculation. For a sizing reference, see the grow room AC sizing guide . Wattage must be between 1 W and 50,000 W. Hours must fall between 0.1 and 24. Rate must be between $0.001 and $10.00/kWh. Inputs outside these ranges will return a validation error rather than a result. This tool calculates operating electricity cost only. It does not include fixture purchase price, bulb replacement intervals, driver or ballast replacement, or depreciation, all of which factor into total cost of ownership. The calculation assumes continuous, uninterrupted operation at the stated wattage for the full duration of the photoperiod. Dimming, duty cycling, or variable-output fixtures will draw less than their rated wattage and must have their actual draw measured at the wall. HID, HPS, and CMH fixtures include a ballast that consumes additional power beyond the bulb's rated wattage. This tool does not automatically add a ballast overhead. Enter the total system draw, not just the bulb wattage. The monthly cost figure uses a fixed 30-day month. Actual utility billing cycles vary and may span 28 to 33 days depending on the provider. The rate field accepts a single flat rate. Tiered utility pricing, time-of-use rates, and demand charges are not modeled. Growers on tiered plans may pay a higher marginal rate once a baseline threshold is crossed. Heat generated by grow lights adds to the cooling load of the space. The electricity cost of running HVAC to offset that heat is entirely separate and is not included in this calculation. For a sizing reference, see the grow room AC sizing guide . Wattage must be between 1 W and 50,000 W. Hours must fall between 0.1 and 24. Rate must be between $0.001 and $10.00/kWh. Inputs outside these ranges will return a validation error rather than a result. This tool calculates operating electricity cost only. It does not include fixture purchase price, bulb replacement intervals, driver or ballast replacement, or depreciation, all of which factor into total cost of ownership. Critical Warnings The daily cost alone is a misleading figure for budgeting. The 30-day monthly cost is the number that belongs in an operating budget, because it aligns with billing cycles, lease terms, and monthly cash flow. A daily figure of $1.51 reads as trivial; the same number compounded to $45.36 per month and $551 per year changes the evaluation entirely. Using the $0.14/kWh default when your actual rate is $0.22/kWh or higher will understate your costs by a significant margin. Always pull the exact rate from your electricity bill before treating the result as final. Rates in California, Massachusetts, Hawaii, and several other states are consistently above $0.20/kWh. Any fixture exceeding 1,500 watts requires a verified circuit capacity check before installation. This tool will display a warning at that threshold, but the calculation itself will still return a cost estimate. A circuit warning in the tool is not a substitute for an electrician's assessment. Minimum Standards The U.S. residential average electricity rate is $0.14/kWh based on EIA 2024 data. Use this only as a comparison baseline, not as a substitute for your actual rate. A photoperiod of fewer than six hours per day is flagged by the calculator because it falls below the light threshold most plant species require to maintain vegetative growth or meaningful photosynthesis. Twelve to eighteen hours per day is the standard range for most indoor crops. Operating grow lights at exactly 24 hours per day will generate a warning. Most crops, including high-value flowering plants, require a defined dark period. Eliminating the dark period does not reduce electricity costs and can impair plant hormone cycles. Competitor Trap: Most grow light cost calculators return only a daily or annual electricity figure and call it complete. The missing output is the monthly cost, which is the unit growers actually use for budgeting and for comparing the operational economics of one fixture type against another. A tool that skips the 30-day number forces the user to do a manual multiplication step, introduces rounding errors, and makes it impossible to directly compare the calculator's output to a utility bill. The monthly cost field is not a convenience; it is a decision-making requirement. Grow lights add a substantial heat load to any enclosed space. High-output fixtures in a sealed environment can push temperatures beyond the optimal range for most crops, which means the HVAC load increases in direct proportion to lighting wattage. The grow room dehumidifier calculator addresses one aspect of that climate management challenge, since humidity and temperature are coupled variables in enclosed grow spaces.

## Limitations and safety

The calculation assumes continuous, uninterrupted operation at the stated wattage for the full duration of the photoperiod. Dimming, duty cycling, or variable-output fixtures will draw less than their rated wattage and must have their actual draw measured at the wall. HID, HPS, and CMH fixtures include a ballast that consumes additional power beyond the bulb's rated wattage. This tool does not automatically add a ballast overhead. Enter the total system draw, not just the bulb wattage. The monthly cost figure uses a fixed 30-day month. Actual utility billing cycles vary and may span 28 to 33 days depending on the provider. The rate field accepts a single flat rate. Tiered utility pricing, time-of-use rates, and demand charges are not modeled. Growers on tiered plans may pay a higher marginal rate once a baseline threshold is crossed. Heat generated by grow lights adds to the cooling load of the space. The electricity cost of running HVAC to offset that heat is entirely separate and is not included in this calculation. For a sizing reference, see the grow room AC sizing guide . Wattage must be between 1 W and 50,000 W. Hours must fall between 0.1 and 24. Rate must be between $0.001 and $10.00/kWh. Inputs outside these ranges will return a validation error rather than a result. This tool calculates operating electricity cost only. It does not include fixture purchase price, bulb replacement intervals, driver or ballast replacement, or depreciation, all of which factor into total cost of ownership. Critical Warnings The daily cost alone is a misleading figure for budgeting. The 30-day monthly cost is the number that belongs in an operating budget, because it aligns with billing cycles, lease terms, and monthly cash flow. A daily figure of $1.51 reads as trivial; the same number compounded to $45.36 per month and $551 per year changes the evaluation entirely. Using the $0.14/kWh default when your actual rate is $0.22/kWh or higher will understate your costs by a significant margin. Always pull the exact rate from your electricity bill before treating the result as final. Rates in California, Massachusetts, Hawaii, and several other states are consistently above $0.20/kWh. Any fixture exceeding 1,500 watts requires a verified circuit capacity check before installation. This tool will display a warning at that threshold, but the calculation itself will still return a cost estimate. A circuit warning in the tool is not a substitute for an electrician's assessment. Minimum Standards The U.S. residential average electricity rate is $0.14/kWh based on EIA 2024 data. Use this only as a comparison baseline, not as a substitute for your actual rate. A photoperiod of fewer than six hours per day is flagged by the calculator because it falls below the light threshold most plant species require to maintain vegetative growth or meaningful photosynthesis. Twelve to eighteen hours per day is the standard range for most indoor crops. Operating grow lights at exactly 24 hours per day will generate a warning. Most crops, including high-value flowering plants, require a defined dark period. Eliminating the dark period does not reduce electricity costs and can impair plant hormone cycles. Competitor Trap: Most grow light cost calculators return only a daily or annual electricity figure and call it complete. The missing output is the monthly cost, which is the unit growers actually use for budgeting and for comparing the operational economics of one fixture type against another. A tool that skips the 30-day number forces the user to do a manual multiplication step, introduces rounding errors, and makes it impossible to directly compare the calculator's output to a utility bill. The monthly cost field is not a convenience; it is a decision-making requirement. Grow lights add a substantial heat load to any enclosed space. High-output fixtures in a sealed environment can push temperatures beyond the optimal range for most crops, which means the HVAC load increases in direct proportion to lighting wattage. The grow room dehumidifier calculator addresses one aspect of that climate management challenge, since humidity and temperature are coupled variables in enclosed grow spaces.

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## Provenance

- Model ID: `tyg-684`
- Model version: `1.0.0`
- Reviewed by: Umer Hayiat
- Page modified: 2026-04-27T18:39:34
- Runtime SHA-256: `79a0f904530954c35d09c70681a9c86afa8e62445b15ae11536a3efda4cd09d7`

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