Cost per hr for lites

Hello one and all — I know I’ve seen somewhere on this site where you can figure the cost to run your lites (certain wattage , certain amt of hrs) using the kWh charges on your electric bill. But to my dismay I cannot find the site and I am asking anyone who may know for his or her guidance…


1 Like

It all depends on what type of lightning your using: HPs, led or cfls. Then you’d have to factor in possibly an a/c, heater or dehumidifier all depending on your climate . Also you’ve got fans running & exhaust fan going 24/7 when flowering & really potent smell. Plus you’ve got the time length of lightning. Some use 18/6, others 14/10, then lastly & the best time 12/12. Without knowing what lights, what temps are normal in your area hard to judge. My bill rose about $30-$50 per month using hps.

For your lights, it’s very simple.
It’s (WATTS x HOURS / 1,000 x KWH rate)

A Kilowatt is 1,000 watts. A Kilowatt Hour is 1,000 watts for 1 hour. 250 watts for 4 hours is 1 KWH.

Find your KWH (Kilowatt Hour) rate on your electric bill.

Look at how many watts your lights actually draw.

You have a 250 WATT light (actual draw).

Your rate is .15/KWH

You run your light for 18 hours per day.

250 watts x 18 hours = 4,500 watts divided by 1,000 = 4.5 KWH x .15 = .675 or about 68 cents per day. Do that for 30 days and it’s about $20.40.

It seems a lot clearer in my head, but hopefully you get the idea.


Less than a eighth on the street and I can smoke that a day



Hope this helps

Estimated Cost Per Month
for Common Grow Room Items

Compare Grow Lights @ $0.25/kWh

Amounts are for if the lights are kept on for 18 hours a day for 30 days (540 hours). In the flowering stage your lights will be on for only 12 hours/day so for those months you’ll only need to calculate for 360 hours (12 hours x 30 days).

MH/HPS Grow Lights

150W - $20/month
250W - $34/month
400W - $54/month
600W -  $81/month
1000W - $135/month

LED Grow Light Examples

Advanced Platinum P150 - 87W - $12/month
Advanced Platinum P300 - 185W - $25/month
Advanced Platinum P450 - 255W - $35/month
Advanced Platinum P600 - 368W - $50/month

Note: Advanced Platinum is just one example of an LED brand that works well for growing cannabis, but you feel free to check out more brands of LED grow lights with true wattage plus yield estimates!)

LED grow lights use less electricity than CFL or fluorescent grow lights, but will the savings in electricity make up for the cost?

Compare Various Fans @ $0.25/kWh

Amounts are for if the fans are kept on for 24 hours a day for 30 days (720 hours):

6" Clip-on fan - 13W - $3/month
10" tabletop fan - 35W - $7/month
4-Inch Exhaust Fan - 70W - $13/month
6-Inch Exhaust Fan - 125W - $23/month

Hydroponic Pumps and Accessories @ $0.25/kWh

Amounts are for if the pumps are kept on for 24 hours a day for 30 days (720 hours):

Air pump - 3W - $0.60/month
Water pump - 26.5W - $5/month
1/13HP Water Chiller - (Capable of lowering an average 20°F in a 30-Gallon tank) - 192W - $35/month

The air pump and water pump in your DWC system for growing marijuana contains a water pump and an air pump which both use electricity

Air Conditioner Examples @ $0.25/kWh

​Amounts are for if the ACs are kept on continuously for 12 hours a day for 30 days (360 hours) - hopefully you don’t have to keep your AC on this often or this long!

7,500 BTU Window Air Conditioner - 670W (for cooling, this unit also has a heating function that takes 1260W) - $61/month for cooling ($114/month for heating)
10,000 BTU Window Air Conditioner - 925W - $84/month
10,000 BTU Portable Air Conditioner - 1000W - $90/month
15,000 BTU Window Air Conditioner - 1330W - $120/month

Figuring Out Cost (Per Grow)

If it’s your first grow, when it comes to figuring out an estimated per-grow cost I recommend planning on it taking 5 months to get to harvest time (even though the average grow is usually about 3-4 months). Although you will hopefully get to harvest sooner, it’s better to estimate for too much money and have it cost less than the other way around!

Five months gives you plenty of time to mess up in the vegetative stage, use a long-flowering strain and still be ready for harvest. After you get some experience you’ll have a much better idea of how long it usually takes to get to harvest using your personal style and preferred strains. One other thing to remember is you’ll use less energy in the flowering stage because your lights will only be on 12 hours a day. You can figure that time out separately if you want, but I’m just going to pretend the lights are on 18/6 to make things simpler.

So now that you’ve begun to figure out your per-month prices, you can multiply them by 5 to get an estimate of how much a whole grow will cost you for each item!

As far as the cost of electricity when growing cannabis, how much money is actually going to come out of your wallet during the grow?

Example Setup ($0.25/kWh)
Remember to look up your local electricity cost because it’s probably much lower!

400W Grow Light - $54/month
2 x 6" Clip-on fans - 13W - $3/month x 2 = $6/month
10" tabletop fan - 35W - $7/month
6-Inch Exhaust Fan - 125W - $23/month

Monthly Electricity Cost: $90
Electricity Cost for 5 Months: $450

That’s a total of $90/month in electricity, so if you multiply that by 5 months you get $450 cost of electricity for the whole grow.

Once you’ve had a grow or two under your belt it’s a good idea to start looking at cost and reward to make sure you’re growing what you need for the price you want.



@garrigan62,great info mate,i have something similar scribbled down lol,the fans an all,love it :slight_smile:


That’s great to here my friend. Any time i can help please ask…ok


Thank you one and all – my kWh per mos. is .10815 — I’ll keep my MH/HPS set up at what I had figured – electric cost per street cost for weed produced is negligible. I love home growin !!

Thanks again