Run Off-Peak Hours

One of the easiest ways to decrease your electricity bill when growing is to run the lights off-peak hours (usually overnight). The first thing to do is check if your energy provider has pricing tiers for electricity consumption. Below are power costs in Ontario, Canada as set by Alectra Utilities.

A 240-Watt LED Board uses 1051 kWh per year (assuming 12/12 light cycle)

= 0.240kWh * 12 hours * 365 days
= 1051 kWh per year

Switching to off-peak hours would result in a cost-saving of $112 per year for a 240W light in Ontario. With a 1000W HPS light, this would result in a savings of $450 per year! Enough to sell your outdated HPS light and get with the times 😉

= ($0.208/kWh – $0.101 kWh) * 1051 kWh
= $0.107 kWh * 1051 kWh
= $112

Measure Consumption

As they say in the business world “if you can’t measure it, you can’t control it“. This holds true with electricity consumption. A consumption measuring device like the Kill-A-Watt (or cheaper generic version) can quickly pay for itself when looking for inefficiencies in your system. This device can also warn of potential problems before they happen. When my exhaust fan was on its way out it started pulling more power as it overheated. This can help you avoid the nasty repercussions of an electronic failure.

Switch to LED Lights

I have written articles on LED vs HPS and the History of LED lights so chances are (since you’re on this website) you are already using LED lights. In case you are still using HPS lights you should calculate how long it would take you to break even on the switch to LED. In my experience LED lights produce an average of 1.6 grams per watt. In the HPS days hitting 1 gram per watt typically required co2 supplementation and a professional grower. Most of my friends still stuck with HPS lights are hitting approx 0.7 grams per watt, so I will compare a 240W QB with a 600W HPS.

Break-Even on 240 Watt QB
= 600W HPS Annual Consumption – 240W LED Annual Consumption
=($0.101/kWh * 0.600 kWh * 12 Hours * 365 days) – ($0.101 kWh * 1051 kWh)
= $265 – $106
= $159

In Ontario where hydro rates are relatively inexpensive, it would take approx 2 years to break even on an LED board assuming you already had an HPS light. When you factor in the initial purchase price the break-even comes closer to 6 months for a new grow with no existing equipment.

Save Heat in the Winter, Exhaust in the Summer

Grow boxes produce heat. Assuming you live somewhere with a cold season this can be used to reduce your heating bill by offsetting how hard your furnace needs to work. In the summer this hot exhaust air should be directed outside so your AC does not have to expend energy cooling it down. I built a DIY ‘air-junction’ to achieve this.

A cover rotates down covering the 5 holes when exhausting outside the house. A block of wood slides back and forth allowing you to direct the airflow. When venting back into the house the box is essentially a massive air filter that oxygenates and cleans the air in your house (assuming you’re running a quality air intake filter).

Run Exhaust Fan on a Digital Temp Controller

Another excellent way to save power is to run your exhaust fan using a Digital Temperature Controller. This way your fan does not waste energy exhausting air during the night phase and when temperatures are in check. I run a 442 CFM 6″ fan which I measured to consume 115 Watts per hour. That is half the power draw of my 240W LED Board!

The fan does not need to run much during the night cycle when plants are not engaging in photosynthesis and there is no heat being generated by your LED boards. Since my night cycle is during on-peak hours, this saves me 12 hours * 115kWh * $0.208. Using the calculator above this results in an annual savings of $105! Enough to buy two or more digital temperature controllers.

If you grow in a cold basement as I do, this also prevents your plants from getting too cold and being stunted during cold winter months.