Vermont marijuana: How to calculate the electricity costs of growing weed at home

Yes, your monthly electric bill could get higher if you add a wattage-sucking grow light to your home appliance list.

At the regular residency rate for Green Mountain Power, a 150 watt grow light can bump a $45 monthly bill to about $60. That’s what happens when a high-wattage light burns for 18 hours a day for a month during marijuana's early vegetative stage, before buds develop. Buds are the final sought-after product.

On July 1 it will be legal in Vermont grow up to six plants at home.

For many casual pot users the extra $15 might easily be absorbed into the varying costs of the average price of weed. An ounce of legal medical marijuana goes for about $350 in Vermont. The new law does not allow for a commercial market for recreational marijuana.

For those still thinking of growing marijuana indoors, here's how to estimate the monthly cost of your potential grow system's energy use.

Here's a cost calculator set up for a small home's monthly rate.

There are a host of cost calculators online such as blitzresults.com, including an energy.gov version built so consumers can estimate what that shiny new light will end up costing. But if you want to get out a calculator, read on.

Figuring out the cost

Take one monthly residential electric bill in Chittenden County for a small home which came to a total of about $45, including fees and credits.

Look at your electric bill.

Scan for kWhr or KWH, which translates to kilowatt hour.

Kilowatt hours (KWH) charge is $36.04 for 29 days or 230 hours.

The rate per kilowatt hour was about $0.15668 plus the energy efficiency charge of about $0.01413 = approximately $0.17.

Lets say, for the sake of the story, that our resident bought an all-in-one package like the 150 watt Mini Sunburst Grow Light Reflector Kit. It says right in the product name how much electrical power (watts) the light will use per hour: 150. But our intrepid grower needs to figure out the kilowatts to estimate the bill.

To get the kilowatts and convert to a decimal: divide 150 by 1,000.

The formula: 150 watts per hour ÷ 1,000 = .15 kilowatts per hour

Cost to run the light per hour: multiply the kilowatts by the rate per hour from the bill.

.15 kilowatts per hour x $.17 rate per hour = $0.0255

There may be months when the lights would need to run for 18 hours or more a day, depending on the grower's chosen gardening methods during a cannabis plant's growth cycle.

Cost per day: multiply the cost per hour by the number of hours per day.

$0.0255 cost per hour x 18 hours = $0.459 cost per hour

Cost per month: multiply $0.459 by 30 days in one month's bill.

$0.459 cost per day x 30 days per billing cycle = $13.77 per month extra

Therefore one light can take a bill from $45 to $58.77.

Remember, outdoors is a viable option so long as the weed is grown in a secure enclosure that is "screened from public view," according to state law.

More: To grow marijuana legally in Vermont, know the law

The formula used in this story was adapted from a post by Gary Heilig at Michigan State University Extension.



