Calculate hydroponic grow room costs from equipment, grow light wattage, electricity price and nutrients: total and monthly cost, cost per plant, payback.
Hydroponics Cost Formula
Hydroponic cost is built from one monthly running cost plus a one-time equipment cost. Everything else the calculator reports is derived from those two numbers.
- MC is the monthly running cost
- LW is the grow light wattage measured at the wall
- LH is the number of hours per day the lights run
- PW is the pump or air stone wattage
- PH is the number of hours per day the pump runs
- 30.44 is the average number of days in a month
- R is the electricity rate per kWh
- N is the monthly spend on nutrients and pH adjusters
- W is the water added per week
- 30.44/7 (approximately 4.348571) is the modeled number of weeks per month; a modeled year is 12 such months
- WR is the water price per 1,000 US gallons or per 1,000 liters; match it to the water-volume unit before using the displayed formula. The calculator converts both to liters internally.
- MD is the monthly spend on seeds, seedlings, and growing medium
- O is the monthly spend on other supplies and maintenance
- TC is the total cost over the period; E included is the equipment cost only when inclusion is selected
- E is the one-time equipment cost
- T is the number of months in the period
- C is the grow cycle length in weeks
- CM is the cycle length expressed in months
- S is the number of cycles you expect the equipment to last
- P is the number of plants in the system
- Y is the harvest weight per plant per cycle
- CPP is the cost per plant per cycle
- CPL is the cost per pound or per kilogram of produce
- BEP is the break-even store price per pound or kilogram
- SP is the actual store price of the same produce
- PB is the payback period in months
The three modes use the same running cost but answer different questions. Total cost mode multiplies the monthly running cost by the number of months and adds the equipment, which tells you what the system takes out of your pocket over a year or a season. Cost per plant mode converts the monthly cost into a per cycle cost, adds a share of the equipment, and divides by plant count and harvest weight, which turns the system into a price per pound you can compare with a receipt. Payback mode values your harvest at store prices, subtracts the running cost, and divides the equipment cost by what is left, which tells you how many months of growing it takes to earn the hardware back.
Electricity is calculated from wattage rather than a flat monthly guess, because lighting almost always dominates an indoor hydroponic budget. Water is a small line item in most home systems, usually under one dollar a month, but it is included so commercial-scale entries stay accurate.
Typical Hydroponic System Costs and Power Draw
These are illustrative budgeting scenarios, not current quotations or guaranteed costs. Replace equipment, tariff, crop and yield assumptions with your own data. The examples use lights on 16 hours a day at $0.18 per kWh plus assumed nutrient spend.
| System | Equipment cost | Light draw | Running cost per month |
|---|---|---|---|
| Kratky jar or passive tote on a windowsill | $40 to $65 | 0 W | $2 to $6 |
| Countertop pod garden, 6 to 12 sites | $100 to $250 | 20 to 45 W | $8 to $18 |
| Deep water culture buckets in a small tent | $250 to $450 | 150 to 300 W | $35 to $70 |
| NFT channel rack, 24 to 48 sites | $400 to $900 | 300 to 600 W | $60 to $130 |
| Indoor vertical tower, 20 to 45 sites | $500 to $1,200 | 300 to 800 W | $70 to $160 |
| Greenhouse NFT bench, 500 plus sites | $5,000 to $25,000 | Sunlight plus supplemental | $250 to $900 |
Break-Even Store Prices by Crop
The number that decides whether a system is worth running is the break-even price: the cost of one pound of your own produce compared with the shelf price of the same item. Whether a crop clears break-even depends on your actual yield, tariffs, labor, downtime and the value of produce you would otherwise buy. The following figures and profitability labels are illustrative assumptions, not crop-specific guarantees. Yields are per plant per cycle unless a season or repeated cut is specified.
| Crop | Yield per plant | Cycle length | Store price per lb | Clears break-even indoors? |
|---|---|---|---|---|
| Loose leaf lettuce | 0.3 to 0.5 lb | 5 to 6 weeks | $2.50 to $4.00 | Only with 30 plus plants per light |
| Romaine or butterhead | 0.6 to 0.9 lb | 7 to 9 weeks | $2.00 to $3.50 | Marginal |
| Basil | 0.15 to 0.25 lb per cut | 4 weeks, repeat cuts | $16 to $32 | Yes, by a wide margin |
| Arugula and spinach | 0.2 to 0.35 lb | 4 to 5 weeks | $4.00 to $8.00 | Usually yes |
| Cherry tomato | 4 to 8 lb per season | 20 to 26 weeks | $3.50 to $6.00 | Yes if grown under sunlight |
| Bell pepper | 3 to 6 lb per season | 18 to 24 weeks | $2.50 to $4.00 | Rarely under lights alone |
| Strawberry | 0.8 to 1.5 lb per season | 30 plus weeks | $3.50 to $6.00 | No, treat as a hobby crop |
Currency selection changes labels only. All costs and store prices must use one currency. Defaults are 12 months and 8 equipment-allocation cycles; enter your own actual costs. The equipment allocation is a simple budgeting share. Add labor, climate control, rent, maintenance and other missing expenses to other monthly costs. Continuous-equivalent payback assumes identical uninterrupted harvests; actual cash recovery occurs at harvest times.
Example Problems
Example 1: yearly cost of a small tent system. The equipment cost $350. The light draws 200 watts for 16 hours a day, the pump draws 25 watts around the clock, and electricity costs $0.18 per kWh. Nutrients run $20 a month, water use is 10 gallons a week at $6 per 1,000 gallons, and seeds, medium, and other supplies add $5 each per month.
Monthly energy use is ((200 x 16) + (25 x 24)) / 1000 x 30.44 = 115.67 kWh, which costs $20.82. Water costs 10 x (30.44/7) / 1000 x 6 = $0.26. Adding nutrients, medium, and other supplies gives a monthly running cost of $51.08, or about $1.68 a day. Over 12 months that is $612.98 in running costs, and $962.98 including the equipment, which averages $80.25 a month across the first year.
Example 2: payback on a 36 site greens system. The equipment cost $600. The light draws 320 watts for 14 hours a day, the pump draws 25 watts continuously, and electricity costs $0.15 per kWh. Nutrients run $25 a month with water use of 10 US gallons a week at $6 per 1,000 US gallons, and $5 each for monthly medium and other costs. Enter these explicitly; optional blank costs now mean zero. You grow 36 plants on a 5-week cycle, harvest 0.5 lb per plant, and the same greens cost $6.00 per pound in the store.
The monthly running cost is $58.46. A 5-week cycle is 5 / (30.44/7) = 1.15 months, so each cycle costs $67.21 to run. The harvest is 36 x 0.5 = 18 lb worth $108.00, so the net saving is about $40.79 per cycle, or $35.47 per month. Recovering $600 of equipment takes 600 / 40.7869 = 14.7 cycles, which is about 16.9 months. The break-even store price is $67.2131 / 18 = $3.73 per pound on running costs alone, and $6.93 per pound if you also want the equipment paid off within the first year.
FAQ
Why does the calculator ask for wattage instead of a monthly electricity bill?
Lighting can be a major running cost; its share depends on the system and which other expenses you include. Entering wattage and hours makes that cost visible and lets you test changes before you make them. As a rule of thumb, every 100 watts running 16 hours a day uses about 48.7 kWh a month, which is roughly $8.80 at $0.18 per kWh. Use the draw measured at the wall, not the marketing equivalent wattage printed on the box, since a light advertised as a 1,000 watt equivalent may pull only 150 watts.
Does hydroponic growing actually save money compared with the store?
It depends on actual harvest, costs, downtime and the store purchases your produce replaces. Simple payback excludes interest, inflation and tax effects. Compare the cost per pound the calculator returns against the break-even price. Leafy greens at $3 per pound need a high plant count per light to beat the store, because the electricity is charged to the whole system regardless of how many sites you fill. The illustrative basil prices above show why high-value crops may be attractive, but they do not establish current local prices or guarantee savings. Filling every site in the system is the single most effective way to lower cost per pound, since it spreads a fixed lighting bill over more produce.
How many cycles should I spread the equipment cost over?
Match it to the shortest lived major component. Reservoirs, frames, and pumps often last five years or more, but LED fixtures lose meaningful output after roughly 30,000 to 50,000 hours and pumps in hard water fail sooner. For a 6-week lettuce cycle running year round, 8 cycles is about one year and gives you a conservative first year figure, while 25 to 35 cycles models roughly three to four years of continuous six-week harvests. Use the expected service life of your actual equipment. Run the calculation both ways: the short figure shows what the first year really costs you, and the long figure shows the steady state cost once the gear is paid off.
