Do Autoflowering Seeds Save Electricity? What Are The Real Advantages Of Autofem Plants?

I’ve seen online seed stores advertising autoflowering/autofem seeds as “saving you electricity” during your grow. Is this true? Are these actually “more efficient plants?” or is this just more marketing jive to convince you to buy seeds that you cannot reproduce easily at home, assuring that you’ll buy more from the seed bank?

Let us look at the facts about the use of electricity during your grow. The math isn’t even complicated, and we don’t even need to know what you pay for electricity per kWH, since we’re talking about your grow location one way or another. We’ll assume that you want to grow a single plant, using 125 Watts of lighting – a typical small, personal medical marijuana home grow.

All you need to keep in mind is that autoflowering cannabis plants are usually grown on a continuous 18/6 light schedule, whereas standard (photoperiodic) marijuana plants must be switched to 12/12 during flowering.

Let’s look at it this way – in the first 4 weeks we’ll assume that either plant (standard or autoflowering) will require 18/6 lighting. This means 28 days at 18 hours of lighting a day. That means you have your lights on for 504 hours during this period. Multiply that by 125 Watts, and you get 63,000 Watts, which is 63 kilowatt hours. If you pay 25 cents per kilowatt, you will pay $15.75 for electricity for these 4 weeks (63 x 0.25).
OK, are you still with me? That’s a little bit of math, but not so bad.

After week 4 (give or take) the standard plants now start using only 12 hours/day of lighting. The Autoflowering plant continues at 18 hours/day. So for the flowering period, we have a very rough estimate of:

• 8 weeks at 12 hrs/day for the standard plant = 672 hours of lighting. That’s 84 kWH.
• 6 weeks at 18 hrs/day for the autoflowering plant = 756 hours of lighting. That’s 94.5 kWH

During flowering, the standard plant actually uses less electricity than the autoflowering variety! With the vegetation and flowering periods together, we get out total power consumption for each variety:

• The standard plant used 147 kWH for the grow.
• The autoflowering plant used 157.5 kWH over the course of the grow.

To be fair, some autoflowering varieties may start flowering after 3 weeks, which would save 126 hours of lighting, or (with a 125 Watts of lighting) about 16 kWH. If we subtract this from the autoflowering total above, we still get 141.5 kWH. Of course, some growers recommend 20 hours of lighting per day for autoflowering strains, which would also increase power use.

To be fair, a sativa-dominant, photoperiodic plant may also take many weeks longer to flower. But considering that there are many strains of standard plants that will finish in less than 12 weeks, the comparison is reasonable.

So the results are that withing a few kilowatt hours of electricity, the power use for either standard or autoflowering plants is essentially the same.

So what are the advantages of an autoflowering plant? Saying that they “save electricity and therefore money” is not quite accurate. What they do offer is a somewhat shorter time from seed to harvest. Autoflowering plants are able to use more hours of light during flowering in order to finish more quickly – this is nature’s design; a way to ensure that the plants would finish flowering before the cold sets in in northern climates. You can figure on a couple weeks less time than a moderately fast finishing photoperiodic plant.

This also means that you don’t need to shell out the $$ for a grow enclosure that makes a 12/12 light/dark cycle possible. If a little light falls on autoflowering plants during the dark cycle, this is not a problem. You could grow them entirely in your living room with no worries about putting the lights on for a midnight trip to the fridge.

What many home growers prefer most about autoflowering plants is their relatively short stature. If your grow space is, shall we say, “vertically restricted”, then a short-growing auto may be just the ticket. The tradeoff is likely to be a smaller harvest of buds.

The disadvantages of autoflowering plants are, in my opinion, that they don’t react well to “topping”, and that you cannot take clones of your plants. These are both results of autoflowering plants having a pre-programmed (if you will) vegetative phase. If you top an auto, the plants has little time to grow multiple top stems before flowering sets in. For this reason, topping autos is not recommended.The same goes for taking clones. You can cut a branch and clone it, but since the age of a clone is always that of the original mother plant, your clone is likely to start flowering before it has any time to increase in size; flowering occurs at a set plant “age”.

In conclusion, I do like autoflowering varieties! However, if I want to harvest more bud from a single, short plant during a grow, I’ll choose a good standard strain, top it or SCROG it, and wind up with a short plant that yields a couple of ounces of great medicine. Your mileage may vary!

If you’d like to learn more about cannabis cultivation, improve your harvests, and get those great bud aromas to shine through in your harvest, then pick up

writer Glenn Panik’s “How To Grow Cannabis At Home: A Guide To Indoor Medical Marijuana Growing”, is available on iTunes here, for the Amazon Kindle or via  Smashwords here.  You can also order the ‘stealth title’ of our information-packed ebook for the Kindle here. 

You will be glad you did; among many things, the book clears through the misinformation on the web and helps you find the right way for you to grow your green meds.

best regards

glenn panik