What a winter of herbs under LEDs costs at Hydro-Québec rates

In winter, without a light, indoor basil wastes away. With a light, people worry about the bill. Good news: the calculation is simple, and the result is almost always small. Here is the formula, the table for a full winter, the effect of taxes and of Rate Flex D, and a detail calculations often forget: the light's heat is not wasted.

Prices are those of Hydro-Québec's Rate D in effect since April 1, 2026, up 3% on average for residential rates, according to the Régie de l'énergie. To choose a device, see our comparison of smart indoor gardens.

The formula in one line

Watts × hours per day ÷ 1,000 = kWh per day. Then multiply by the price per kWh.

Example: a 24 W light on for 16 hours uses 24 × 16 ÷ 1,000 = 0.384 kWh a day.

The price per kWh, for its part, depends on your total consumption. Under Rate D, energy has two prices since April 1, 2026:

• 7.065¢ per kWh for the first 40 kWh a day, multiplied by the number of days in the billing period;
• 11.142¢ per kWh for the rest.

The system access charge, 46.154¢ a day, does not change whether or not you add a light. To know which price applies to your light, divide the consumption shown on your bill by the number of days: below 40 kWh a day, each extra kWh costs 7.065¢; above, it costs 11.142¢. In winter, in an electrically heated home, the second price often applies.

The table for a full winter

Assumptions: November 1 to March 31, or 151 days, at 16 hours of light a day, before taxes. For Gardyn, we use the monthly consumption range published by the brand.

The Click & Grow figures match the brand's own: 3.8 kWh a month for the Smart Garden 3 and 6.2 kWh for the Smart Garden 9, which corresponds to about 16 hours of light a day. For the Smart Garden 3, a whole winter's electricity therefore costs less than a single package of basil at the grocery store, sold for $2.99 at Super C the day we checked.

With taxes

On the bill, the GST (5%) and QST (9.975%) are added, or 14.975% more. The 48 W shop light at 11.142¢ thus goes from $12.92 to $14.85 for the winter; the Smart Garden 3, from $2.15 to $2.47; a large Gardyn tower, at worst, from $38.14 to $43.85.

The light's heat is not wasted

A light turns almost all the electricity it uses into heat, including the light itself, which ends up absorbed by walls, furniture and plants. In the twin test houses of the Canadian Centre for Housing Technology in Ottawa, a study by CANMET, at Natural Resources Canada, measured that 83 to 100% of the energy used for lighting ended up as internal heat gains. In winter, that heat reduced the heating system's work by almost as much.

What that means for your grow light:

• Home heated with electric baseboards: during the heating season, the light's heat replaces a good part of the baseboards' heat. The net cost of your light then approaches zero, as long as the heating is running.
• Home heated with a heat pump: the offset is smaller, because a heat pump produces more than one kWh of heat for each kWh of electricity it uses. The light's net cost drops, without disappearing. We explain these systems in our guide to heat pumps in Quebec.
• Gas, oil or wood heating: the light's heat replaces a little fuel rather than electricity.
• In summer: it is the reverse. The same study measured that about 80% of the heat gains from lighting added to the cooling load. A good reason to switch off the lights when the sun comes back.

Full example: the shop light over a bin

Take the 48 W LED shop light from our DIY hydroponic system, on for 16 hours a day from November 1 to March 31, in a bungalow heated with electric baseboards that goes over 40 kWh a day in winter.

• Consumption: 0.768 kWh a day × 151 days = 116 kWh.
• Billed cost: 116 kWh × 11.142¢ = $12.92, or $14.85 with taxes, about 10¢ a day.
• Net cost: since the whole period falls in the heating season, the light's heat replaces a good part of the baseboards' heat. The real extra cost is therefore well below that $14.85.

In an apartment heated with hot water by the building, which stays below 40 kWh a day, the calculation is done at 7.065¢ instead: $8.19 for the winter, or $9.42 with taxes, with no offset on your own heating bill.

What about Rate Flex D?

Under Rate Flex D, winter runs from December 1 to March 31. Outside peak events, energy costs less than under Rate D: 4.886¢ per kWh up to 40 kWh a day, then 9.103¢. During peak events, which can occur between 6 and 10 a.m. and between 4 and 8 p.m., for a maximum of 120 hours per winter, the kWh jumps to 46.463¢.

Should you turn off your light during peaks? Run the numbers: a 48 W light on during a 4-hour event uses 0.192 kWh, or 8.9¢. Even if it stayed on for all 120 possible peak hours in a winter, the extra cost compared with the off-peak price would be about $2. Not worth complicating your life with your timer. For large appliances, on the other hand, peaks do matter: we explain how to take advantage of them in saving energy in winter.

The real cost: electricity, device and pods

Electricity is almost always the smallest line. What adds up is the rest:

• The device: $154.95 for a Smart Garden 3, $299.95 for a Smart Garden 9 on Click & Grow's Canadian store, and $96.79 for our DIY hydroponic system, light included.
• Pods: $16.95 for 3 at Click & Grow, or $5.65 per plant.
• Membership: at Gardyn, US$29 to US$39 a month for the Home, or US$145 to US$195 for a five-month winter, far more than its electricity.

A membership or exclusive pods can therefore cost ten times more than the electricity. We explain how to avoid that trap in the proprietary pod trap.

5 ways to lower the bill

1. Choose a light sized to your plants. No point running 50 W for three pots: light that falls beside them is wasted.
2. Set the timer to 12 to 16 hours, as Iowa State University recommends, not 24.
3. Bring the light closer to the leaves, 15 to 30 cm according to Iowa State: more useful light for the same electricity.
4. Choose an efficient LED. Efficiency is measured in µmol/J; we explain how to read it in LED grow lights: reading the real specs.
5. Switch off in spring. When the sun returns to the windowsill, and the light's heat no longer helps with heating, cut the hours or put the light away.

For the rest of the house, our tips for saving electricity save far more than a light switched off. And if you are wondering what other small appliances cost, we did the same exercise for the electric composter.

Sources

• Grille tarifaire au 1er avril 2026 (rate grid, in French), Hydro-Québec, 2026.
• Rate Flex D, Hydro-Québec, accessed October 21, 2026.
• Tarifs d'électricité d'Hydro-Québec : la Régie de l'énergie fait le point (news release, in French), Régie de l'énergie, 2026.
• Benchmarking of Energy Savings Associated with Compact Fluorescent Lighting in Homes, Anil Parekh, CANMET, Natural Resources Canada, ACEEE, 2006.
• The Smart Garden 3 (product page, Canadian store), Click & Grow, accessed October 21, 2026.
• The Smart Garden 9 (product page, Canadian store), Click & Grow, accessed October 21, 2026.
• AeroGarden Harvest (product page), Scotts Miracle-Gro, accessed October 21, 2026.
• AeroGarden Bounty Elite (product page), Scotts Miracle-Gro, accessed October 21, 2026.
• FAQ, Gardyn, accessed October 21, 2026.
• Gardyn Home 4 and memberships, Gardyn, accessed October 21, 2026.
• How can I provide more light for my herbs indoors?, Aaron Steil, Iowa State University Extension, 2024.
• Irrésistible Organic Basil (product page), Super C, accessed October 21, 2026.