The real electricity cost of indoor growing

Lighting is 70-85% of your power bill. A countertop herb setup runs about $8/month. A serious grow tent costs $30-80/month. The math by system size.

Every indoor grow runs on electricity. The pump, the air stone, the fan, and above all the lights. Before scaling up from a windowsill herb jar to a 120 cm grow tent full of tomatoes, it's worth knowing what the power bill will actually look like. The numbers are lower than most people expect for small setups and higher than people budget for in large ones.

Where the electricity goes

Grow lights: 70-85% of total power draw. This is the dominant cost in any indoor system. A 100W LED running 16 hours per day consumes 1.6 kWh. A 300W panel running 14 hours uses 4.2 kWh per day. Lighting is non-negotiable, and unlike pumps and fans, there's no way to reduce runtime without reducing crop performance.

Water pump: 5-10% of total draw. Most hydroponic pumps run 10-60 watts. Small submersible pumps for countertop systems draw 10-20W. Larger pumps for multi-bucket or NFT systems draw 30-60W. Some systems run pumps intermittently (15 minutes on, 45 minutes off), which cuts pump electricity by 75%. DWC systems don't need a water pump at all, just an air pump.

Air pump: 2-5%. Aquarium air pumps for DWC or reservoir aeration draw 3-10 watts and run continuously. Negligible cost, roughly $0.50-1.50 per month.

Exhaust fan and circulation fan: 5-10%. An inline exhaust fan for a grow tent draws 30-100W. A small clip-on circulation fan draws 10-20W. Both may run 24/7 or on a timer.

Heater or chiller: variable. In cold environments, a small heater for the reservoir or grow space adds 50-200W. A water chiller for root zone cooling in summer adds 100-400W but cycles on and off. These are the wildcard items that can significantly increase electricity costs in extreme climates.

Cost by system size

These estimates assume an average US residential electricity rate of $0.15 per kWh and LED lighting. Your actual cost will vary based on local rates (check your utility bill) and equipment choices.

Countertop herb garden (4-8 plants)

Equipment: 20-40W LED panel, 5W air pump, no water pump (Kratky) or 10W pump. Daily consumption: 0.5-1.0 kWh. Monthly cost: $2-5.

This is the cost of a dim light bulb running most of the day. Most growers don't even notice it on their bill.

Small grow tent (60 x 60 cm, 8-12 plants)

Equipment: 100-150W LED, 10W air pump, 15W circulation fan, maybe a small exhaust fan. Daily consumption: 2.0-3.0 kWh. Monthly cost: $9-14.

Still modest. Comparable to running a mini fridge.

Medium grow tent (120 x 60 cm, 12-24 plants)

Equipment: 200-300W LED, 10W air pump, 20W exhaust fan, 15W circulation fan, 20W water pump. Daily consumption: 4.0-6.0 kWh. Monthly cost: $18-27.

This is where lighting cost becomes clearly visible on the electricity bill. The LED is drawing 200-300W for 14-16 hours per day.

Large grow room (120 x 120 cm or multi-shelf, 24-48 plants)

Equipment: 400-650W total LED (one or two fixtures), 30W air pump, 60W exhaust, 20W circulation, 40W pump, possible dehumidifier (200W). Daily consumption: 8-15 kWh. Monthly cost: $36-68.

At this scale, you're running a noticeable electrical load. A 600W LED alone costs about $1.15 per day at 12 hours. Add climate control equipment in hot or humid environments and costs can push toward $80-100 per month.

How to calculate your own cost

The formula is simple:

Watts x hours per day / 1000 = kWh per day

kWh per day x 30 = kWh per month

kWh per month x your electricity rate = monthly cost

Add up each piece of equipment: light, pump, fan, heater, anything with a plug. Multiply each by its daily runtime. Sum the kWh values.

Your electricity rate is on your utility bill, usually expressed as cents per kWh. The US national average is about $0.15/kWh, but it ranges from $0.10 in some southern states to $0.30+ in Hawaii, California, and the Northeast.

The running cost calculator automates this calculation for hydroponic and aquaponic systems, letting you input each piece of equipment with its wattage and runtime.

Is it worth it

For herbs, the economics are clear. A countertop Kratky setup costs $2-5 per month in electricity and produces fresh basil, mint, and cilantro that would cost $3-5 per week at a grocery store. The system pays for itself in fresh produce within the first month.

For leafy greens (lettuce, spinach, kale), the electricity cost is reasonable but the grocery store comparison is less favorable. A head of lettuce costs $1-2. You need to produce a lot of lettuce to offset a $20-30 monthly electric bill plus the initial setup cost.

For fruiting crops (tomatoes, peppers, strawberries), the electricity cost is highest because these plants need the most light. The payoff isn't financial, since grocery store tomatoes are cheap. It's qualitative: homegrown hydroponic tomatoes taste dramatically better than commercial ones picked green and shipped across the country.

The real calculus isn't "will I save money on groceries." For most home growers, the answer is "probably not at small scale." The value is having ultra-fresh produce year-round, knowing what's in your food, and the satisfaction of growing it yourself.

Reducing electricity cost without reducing yield

Use natural light when possible. A south-facing window provides meaningful supplemental light (reducing the hours your LED needs to run) for leafy greens and herbs. A windowsill Kratky setup with a 20W LED running 8 hours to supplement natural daylight costs half as much as the same setup running 16 hours in a closet.

Match light to crop needs. Lettuce needs a DLI of 12-17 mol/m2/day. Tomatoes need 22-30. Running a 300W LED for 16 hours to grow lettuce is like driving a pickup truck to buy groceries. A 100W light at 14 hours provides plenty for lettuce and costs a third as much to run.

Run lights during off-peak hours. Some electricity providers offer time-of-use pricing where overnight rates are 30-50% cheaper than daytime rates. Plants don't care what time the lights come on. Running lights from 10 PM to 12 PM (overnight into late morning) can reduce the per-kWh cost substantially in markets with time-of-use pricing.

Right-size the pump. A pump rated for a 1000-liter pond is overkill for a 50-liter reservoir. It draws more watts than needed and generates excess heat. Match pump flow rate to system requirements. A small NFT system needs 300-500 L/h, not 2000 L/h.

Insulate the reservoir. In systems that use a chiller, insulation reduces the chiller's runtime by slowing heat absorption. Less chiller runtime means less electricity. Wrapping a reservoir in rigid foam board can cut chiller electricity use by 20-30%.

Tracking costs over time

The first month of running an indoor grow is the most expensive (equipment purchases, initial nutrient supplies, possibly a higher-than-expected electricity bill). By month 3-4, the per-unit cost of produce drops as you optimize light hours, pump runtime, and nutrient usage.

Keep a simple log: monthly kWh from your electricity meter (or estimate from the formula above), seed and nutrient costs, and harvest weight. After a few months, you'll know your actual cost per kg of lettuce or per bunch of basil. For most home herb growers, the number ends up remarkably low, often under $1 per harvest that would cost $3-4 at a store.

The running cost calculator automates the electricity calculation for hydroponic and aquaponic systems, letting you input each piece of equipment with its wattage and runtime.