Calculate Electricity Costs of Growing Weed

Last updated: 4 March 2022

Calculating electricity costs

While you might not think so at first, when starting to think of growing your own cannabis, you’re soon going to come to the realization that the biggest part of your grow room’s budget will be devoured not by the cost of seeds or fertilizers, and even not the cost of equipment. The part that makes indoor cannabis growing quite a costly hobby is, in fact, electricity.

Think about it and you’ll see why. Cannabis is a light-loving plant whose yield heavily depends on the number of lumens it receives. These green bushes require powerful lights of 200, 400, and even more Watts to be running for the most part of the day, for months on end! And besides the lights, there’s also other equipment that needs to be plugged into your house’s electricity in order to work.

Therefore, you will greatly benefit from calculating your electricity costs beforehand. See why and how to do so next.

Why Do You Need to Calculate Electricity Costs?

Careful planning is an essential part of a successful grow. Pro growers will say that budget planning is a big part of that.

If your budget doesn’t allow you to spend unlimited amounts of money on electricity, you’ll need to calculate the electricity costs of your future grow beforehand. That way, you won’t be unpleasantly surprised when the electricity bill arrives.

top 8 really potent yet short sativa strains to grow indoorsREAD NOW

Planning electricity costs can also help you equip a grow room that will serve your growing needs without breaking your budget. If you know the wattage of the gadgets you’re planning to get and the number of hours you plan to leave them on daily, you can calculate what part of the electricity bill they’re going to make up. That way, you can prioritize some parts of the grow room over others and change them for options that consume less power. When this needs to be done, growers usually prioritize grow lights, allowing them a higher wattage, while cutting down a little on fans or exhaust.

Too high of an electricity bill can become a surprise not just for you, but also for local authorities. If growing cannabis in your area is forbidden by law, a sudden leap in power usage could lead to raised suspicions. To avoid that, calculate your electricity costs beforehand and try to keep them under a certain point that you believe won’t be grounds for suspicion.

A Simple Formula to Calculate Electricity Costs

Total electricity cost of 1 gadget

Now for the fun part! The amount of electricity to grow weed will vary from grower to grower, but there’s this universal formula. All you need to know is how much you pay for your electricity (kWh), how much electricity your equipment uses, how long you keep it on daily, and what kind of strain you’re growing. Here’s the formula:

Electricity Price x Number of Hours x (Watts / 1000)

To learn the price of electricity in your area, you can ask your provider or simply check one of your previous electricity bills.

To fill in the “Watts,” just check the box your equipment came in. This information may also be stated on the gadget itself.

cbg and cbg strainsREAD NOW

“Number of hours” stands for how long the equipment is turned on for daily, monthly, or during the whole grow, depending on the period you want to learn the electricity costs for. For example, if your question is “How much does electricity cost per month to grow weed?” then you need to insert the number of hours per month, and if you want to know the electricity cost for growing one weed plant, you’re going to use hours in the whole lifecycle of your plant. This is exactly what we’re going to do with an example below.

Real-Life Example

For our example, we’re going to use the following data:

  • A photoperiod Indica-leaning plant: 3 months in veg (18/6) and 70 days in flower (12/12).

  • The average electricity rate in the US: 10.42 cents per kilowatt-hour.

  • A grow room that includes one 400W LED lamp, two 40W oscillating fans (running 24/7), and a 120W exhaust system.


Let’s see how much this setup is going to cost us in electricity. We’re going to start with calculating the cost of lights during the whole grow:

  • 3 months (90 days) of the vegetative period X lights running 18 hours a day = 1,620 hours of lights on for the vegetative stage.

  • 70 days of the flowering period X lights running 12 hours a day = 840 hours of lights on in the flowering stage.

  • 1,620 + 840 = 2,460 hours of lights on in total.

  • $0.1,042 kWh X 2,460 X 400 W / 1,000 = $102.5.

Now let’s continue with our two oscillating fans:

  • 160 days total X 24 hours of fans on a day = 3,840 hours of fans on throughout the whole grow.

  • $0.1,042 kWh X 3,840 X 40 W / 1,000 = $16

  • $16 X 2 fans = $32.

And finally, our 120W exhaust system:

  • 160 days total X 24 hours of exhaust system on a day = 3,840 hours of exhaust on throughout the whole grow.

  • $0.1,042 kWh X 3840 X 120 W / 1,000 = $48.

Total electricity costs for this set up for 3 months of veg and 70 days of flowering:

$102.5 + $32 + $48 = $182.5.

After you do a similar calculation, you’ll see whether power costs fit into your budget. If not, you can try picking some other equipment or following our tips below.

how long do the effects of edibles last?READ NOW

How to Save on Electricity Costs

After you do a similar calculation for yourself, you’ll see whether power costs fit into your budget. If not, you can try picking some other equipment or following these tips.

Tip 1: Keep Your Plants Healthy

Remember that every pest or sickness prevents your cannabis from maturing quicker. If you keep your plants healthy, they will finish sooner, therefore saving your money. This is especially important if you grow photoperiod strains; if you don’t follow the strict 12/12 lighting schedule during flowering, your plant may re-veg and take weeks to start flowering again.

Tip 2: Choose a Quicker Strain

If you want to spend less on electricity but don’t want to opt for weaker lights, try growing quicker strains. Indicas are typically faster than Sativas, and they can sometimes finish their flowering cycle in 8 weeks. Autoflowers are absolute champions here: from seed to harvest will only take 2-3 months. Here are some examples of strains that will help you save money:

Smoothie Auto (FastBuds)

Potent at 24% THC, Smoothie Auto is a mouthwatering sweet strain with a refreshing mango flavor and a strong cerebral high. This strain won’t break the bank either – it will finish in no longer than 70 days under grow lights.

Sugar Black Rose Early Version (Delicious Seeds)

Designed specifically to deliver quick harvests, Sugar Black Rose Early Version is a photoperiod strain with an extra speedy flowering time of just 45 days. After such a short period, you’ll harvest jars and jars of grape-flavored bud with 25% THC and a bright, instantaneous head high.

Godzilla Cookies Auto (Herbies Seeds)

Finishing in under 75 days, Godzilla Cookies Auto still brings incredible results with 27% THC buds and heavy harvests of up to 600g/m2 (2oz/ft2). Expect long-lasting euphoric effects and an incredible flavor of cookies and citrus.

Tip 3: Be Smart About the Lights

Do your research. Some lights are way more efficient than others – for example, HPS or full-spectrum LED. If you go with them, you might consider cutting down the number of light hours a day from 20 to 18 without losing any yields. Also, you don’t need to give too much light to your cannabis from the very start: seedlings will grow perfectly under 100W.

Tip 4: Reduce the Number of Fans

While seedlings will do great with just one fan, bigger plants usually require more. However, depending on the size and setup of your grow room, you might be able to place just one fan strategically so that the air circulation goes through the whole area. In this case, you won’t have to add another fan and will be able to save some more money.

How Much Does Growing Weed Cost in Electricity? Get Calculating

Now you know that it’s easy to find out how much growing weed will cost you in electricity, and it has lots of benefits too. We have readers from all over the globe, and it would be fun to learn how everyone pays for the electricity in their grow room – let us know in the comments below!

Herbies Head Shop expressly refuses to support the use, production, or supply of illegal substances. For more details read our Legal Disclaimer.

So you are saying get an autoflower as will take 2-3 months, but normal will finish in 8 weeks, sorry this does not make any sense.If you want to spend less on electricity but don’t want to opt for weaker lights, try growing quicker strains. Indicas are typically faster than Sativas, and they can sometimes finish their flowering cycle in 8 weeks. Autoflowers are absolute champions here: from seed to harvest will only take 2-3 months.
Hello Monchoon,You've mentioned that autos will take 2-3 months, and then you've mentioned that harvesting them may 2-3 months, that's what we mentioned in the article - autos sometimes finish their flowering cycle in 8 weeks. They are good for a fast results and easier for the beginner and/or in a limited space
Autos aren't as cheap to grow as people say. Many do not finish in the advertised time & also you have to have yiur lights on for longer 20 hours a day, with some people running them for 24 hours.Compare this to a Sativa which can be grown from seed to harvest on 12/12, there are plenty of them & 3 months of 12/12 is a lot cheaper than running autos 20-24 hours a day. Depending on your growing style, for example 9-12 & even 16 plants a square metre generally need no veg & can go straight into 12/12 without affecting yield at all. Remember, the less plants per square metre generally means more veg so 4-5 plants will need about a month veg & two months on 12/12. It's all about how you grow but I would advise people not to fall into the misconception that Autos are cheaper to grow because they're not, usually always using far more electricity.Sorry, I've been growing for 25 + years & can say with confidence that Autos are not cheaper to grow when it comes to electricity.The advantage of Autos is they pretty much grow themselves, meaning people with little to no experience can grow them.Also LST & scrogging require sometimes 2-3 months training then flower. How is that cheaper than growing normally when if you know what you're doing you can pull exactly the same amount of final yield.A short flowering Indica of say 45-50 days with a months veg is also cheaper as is a "fast version"Growers, don't be fooled by the hype that Autos are cheaper because they aren't. Do the maths & you will see for yourself.Peace PJ
She it stoners say, autos 8-12 weeks they done, seed to harvest, I have Mendocino shrunk it flowers in 7 sometimes 5 after 2wks veg. Autos require 20hrs light a day Mendo girl 18for 2 the 12bfor 7, heaps cheaper growing photo indoors
Add a comment

How to post a comment

Thank you for leaving a comment for us!

Your feedback will be posted shortly after our moderator checks it.

Please note that we don’t publish reviews that:

  • Are written in ALL CAPS
  • Use aggressive or offensive language
  • Promote other websites (include contact details or links)