Grow Room Electricity Cost Calculator

Work out your grow room electricity cost and circuit load in one place. Add lights, fans, HVAC, and pumps to see kWh and cost per day, month, year, and grow cycle, plus whether your breakers can handle it. Questions? Talk to a Grow Expert.

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Grow Room Electricity Calculator

Add devices below. kWh, costs, and circuit load update live as you type.

Your State i Fills in the average electricity rate for your state from the U.S. Energy Information Administration (EIA, July 2026 data). Your actual rate may differ, so check your bill when you can.

Rate Type i Residential for home grows. Commercial if your grow is on a business account, which is usually billed at a lower energy rate.

Electricity Rate ($/kWh) i Set automatically when you pick a state, or type the rate from your utility bill (look for ¢/kWh). The U.S. residential average is about $0.18/kWh.

Days per Month i How many days per month you run your grow. Use 30 for always-on, or fewer if you cycle your space.

⚡ Advanced: Time-of-Use (TOU) Pricing

Peak Rate ($/kWh) i Your on-peak rate, usually 4 to 9 PM on weekdays. Check your utility bill for exact hours and rates.

Peak Hours per Day i How many hours per day your grow runs during peak pricing. If lights run 18h/day and 5 of those hours are peak, enter 5.

TOU cost uses your peak rate for peak hours and your standard rate for off-peak hours, applied proportionally per device.

	Device i Name your device (e.g. "LED Light 1"). Optional, for your reference only.	Watts i The running wattage from the spec sheet or device label. For AC units and dehumidifiers, use running watts, not startup watts.	Hrs/Day i Hours per day the device is switched on. Lights run 18h in veg and 12h in flower. Always-on devices like fans = 24.	Duty % i How much of its on-time the device actually draws full power. Lights and fans are 100%. Dehumidifiers, AC, and heaters cycle on and off, often 40 to 70%. Lowers kWh and cost, not circuit load.	Qty i Number of identical units. If you have 4 fans of the same wattage, enter 1 row with Qty = 4.	Circuit i Which circuit (breaker) this device plugs into. Set each circuit's breaker size and voltage in the Circuit Load Check below.	Light i Check for grow lights. Light rows follow your veg and flower schedule in the Grow Cycle Cost tool.	kWh/Day i Formula: (Watts ÷ 1,000) × Hours × Duty % × Quantity. This row's share of your daily electricity use.

Swipe the table sideways to see Duty %, Circuit, and kWh columns.

Total kWh/day 0.00 kilowatt-hours

Cost / Day $0.00 per day

Cost / Month $0.00 per month

Cost / Year $0.00 per year

Circuit Load Check

Shows amps on each circuit using running watts. Continuous loads like lights and fans should stay at or under 80% of the breaker rating.

Circuit A No devices

Breaker

Voltage

0%80%100%

Load0 W

Amps0.0 A

Of breaker0%

Estimates only. Results use running watts. Compressor equipment (AC, dehumidifiers, chillers) can pull 2 to 3 times its running watts for a moment at startup, and other outlets on the same breaker add load too. Have a licensed electrician confirm circuit capacity before adding major equipment.

🌱 Cost per Grow Cycle

Veg Weeks i How many weeks your plants stay in vegetative growth.

Veg Light Hours/Day i Light-on hours during veg. 18/6 is the most common schedule.

Flower Weeks i How many weeks of flowering until harvest. Most photoperiod strains run 8 to 10 weeks.

Flower Light Hours/Day i Light-on hours during flower. 12/12 is standard for photoperiod plants.

Veg Cost$0for veg

Flower Cost$0for flower

Cycle kWh0kilowatt-hours

Total per Cycle$0seed to harvest

Rows checked as Light follow this schedule. Everything else uses its own Hrs/Day. Uses your current rate, including TOU if it's on.

💡 LED Upgrade Savings

Current Fixture Watts i Actual draw of the fixture you'd replace. A 1000W HPS on a digital ballast draws about 1,050 to 1,100W at the wall.

New LED Watts i Actual draw of the replacement LED from its spec sheet. A 1000W HPS replacement typically draws 600 to 700W.

Number of Fixtures

Light Hours/Day i Average hours per day over the year. A veg and flower mix usually averages 12 to 14.

LED Price per Fixture ($) i What you'd pay for each new LED fixture. Used to work out how many months until the upgrade pays for itself.

Watts Saved0watts

kWh Saved0per year

Money Saved$0per year

Payback—months

Counts lighting power only. LEDs also put out less heat, so AC savings usually make real payback faster. Shop LED grow lights

Remember my inputs

How to use this calculator

Set your rate. Pick your state to fill in the EIA average, or type the exact rate from your utility bill.
Add your devices. Use a preset or a blank row and enter running watts, hours per day, and quantity. Set a duty cycle for gear that cycles on and off, and check Light for grow lights.
Assign circuits. Pick a circuit for each device, then set that circuit's breaker size and voltage.
Check your results. Cost tiles update live. Circuit cards show amps and flag anything over the 80% continuous limit.
Plan ahead. Open Cost per Grow Cycle for seed-to-harvest cost, LED Upgrade Savings for payback time, and TOU if your utility charges peak rates.
Save or share. Copy Results gives a text summary with a shareable link. CSV Export and Print are there too.

Formulas: kWh/Day = (Watts ÷ 1,000) × Hours/Day × Duty % × Quantity. Monthly Cost = kWh/Day × Rate × Days. Amps = Watts ÷ Volts. Continuous load limit = Breaker Amps × 80%.

📊 Device Cost Breakdown Chart ▾

Add devices above to see the cost breakdown chart.

Each bar is one device row's daily electricity use, labeled with its daily cost. Taller bars are your biggest cost drivers and the best targets for efficiency upgrades. Hover or tap a bar to see the exact kWh and cost.

Frequently Asked Questions

How much electricity does a grow room use?

A typical 4×4 tent with a 400W LED, fans, and a dehumidifier uses roughly 10–14 kWh per day, about $55–$75 per month at the U.S. average of $0.18/kWh. A 10×10 room with 2,000W of lights, HVAC, and CO₂ can pass 100 kWh per day, or over $500 per month. Add your own devices above to get your exact number.

How do I calculate grow room electricity cost?

Divide each device's wattage by 1,000, multiply by its daily run hours and quantity to get kWh per day, then multiply by your electricity rate. Add up every device for your total. Formula: kWh/day = (Watts ÷ 1,000) × Hours × Quantity. Monthly cost = kWh/day × rate × days. This calculator does all of it automatically.

What is the difference between kWh and amps?

kWh measures energy used over time, which is what you pay for on your bill. Amps measure how much current a device draws at one moment, which is what your breaker limits. A 1,000W light running 12 hours uses 12 kWh, but at any instant it draws about 8.3 amps on a 120V circuit. Check amps to avoid tripping breakers and kWh to estimate cost.

How many watts can I run on a 20-amp circuit?

A 20-amp, 120V circuit can carry 2,400 watts total, but loads that run 3 hours or more, like grow lights and fans, should stay at or under 80%, which is 1,920 watts. A 15-amp circuit tops out at 1,440 watts continuous, and a 30-amp 240V circuit at 5,760 watts. Have a licensed electrician confirm before adding major equipment.

What is duty cycle and why does it matter?

Duty cycle is the share of its on-time that a device actually runs at full power. Lights and fans run at 100%, but dehumidifiers, air conditioners, and heaters cycle on and off as they hit their setpoint, often running 40–70% of the time. Entering a duty cycle gives a more realistic kWh and cost estimate. It doesn't lower circuit load, since the unit still draws full amps while running.

What uses the most electricity in a grow room?

Grow lights typically account for 50–70% of total electricity in a grow room. HVAC, meaning air conditioners and dehumidifiers, is usually the second-largest load at 20–35%. Fans, CO₂ equipment, and pumps make up the rest. The bar chart above shows exactly which devices drive your bill.

How can I reduce my grow room electricity bill?

Switch to LED grow lights, which use 40–60% less power than HPS or MH for similar output. Use programmable timers, run lights during off-peak hours if you have time-of-use billing, right-size your HVAC to your actual heat load, and use EC fans that ramp down automatically. The LED Upgrade Savings tool above shows your payback time.

What is a Time-of-Use (TOU) electricity rate?

TOU pricing charges different rates for peak and off-peak hours. Peak hours, typically 4–9 PM, can cost 2–3× more than off-peak. Growers using timers can shift lights-on time to off-peak windows, for example running 7 PM to 1 PM instead of 6 AM to midnight, saving 20–40% on lighting costs. Use the Advanced TOU section above to model this.

⚡ Grow Room Device Power Reference Typical watts, amps, and monthly cost

Typical wattage, amps at 120V, run hours, and monthly cost at $0.18/kWh for common grow room devices.
Device	Typical Watts	Amps @ 120V	Hours/Day	kWh/Month (est.)	Cost/Month @ $0.18
LED Grow Light (budget 2×4)	150–200W	1.3–1.7 A	18h	81–108 kWh	$15–$19
LED Grow Light (mid 4×4)	240–320W	2.0–2.7 A	18h	130–173 kWh	$23–$31
LED Grow Light (pro 4×4)	480–630W	4.0–5.3 A	18h	259–340 kWh	$47–$61
HPS 600W	600–660W	5.0–5.5 A	18h	324–356 kWh	$58–$64
HPS 1000W	1,000–1,100W	8.3–9.2 A	18h	540–594 kWh	$97–$107
Mini-Split AC (9,000 BTU)	700–1,000W	5.8–8.3 A	10–16h	210–480 kWh	$38–$86
Portable AC (8,000 BTU)	900–1,200W	7.5–10 A	10–16h	270–576 kWh	$49–$104
Dehumidifier (30-pint)	250–350W	2.1–2.9 A	24h	180–252 kWh	$32–$45
Dehumidifier (70-pint)	600–800W	5.0–6.7 A	24h	432–576 kWh	$78–$104
Inline Fan (6-inch)	40–80W	0.3–0.7 A	24h	29–58 kWh	$5–$10
CO₂ Controller/Solenoid	20–30W	0.2–0.3 A	24h	14–22 kWh	$2.60–$3.90
Water Pump (submersible)	20–150W	0.2–1.3 A	0.25–2h	0.2–9 kWh	$0.03–$1.62

AC and dehumidifier figures assume the unit runs the full hours shown. Real use is usually lower because compressors cycle. $0.18/kWh is the U.S. residential average (EIA, July 2026).

🔌 Circuit Capacity Reference How many watts a breaker can carry

Maximum watts by breaker size and voltage, with the 80% continuous load limit used for grow lights, fans, and other equipment that runs 3+ hours at a time.
Breaker	Voltage	Max Watts (100%)	Continuous Limit (80%)	Continuous Amps
15A	120V	1,800 W	1,440 W	12 A
20A	120V	2,400 W	1,920 W	16 A
30A	120V	3,600 W	2,880 W	24 A
20A	240V	4,800 W	3,840 W	16 A
30A	240V	7,200 W	5,760 W	24 A
40A	240V	9,600 W	7,680 W	32 A
50A	240V	12,000 W	9,600 W	40 A

Based on the NEC 80% continuous load rule. Local code and wire gauge can change what's allowed, so confirm with a licensed electrician.

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