Grow Room Cost Calculator

Setting up an indoor grow room typically costs $50 to $180+ per square foot of grow space, so a small hobby closet might be a few hundred to a couple thousand dollars, a dedicated standard room runs several thousand to $20,000+, and a large or commercial-grade space can reach tens of thousands. The biggest driver is the setup level (hobby vs. sealed room vs. professional), followed by the lighting and climate systems. Just as important, an indoor grow has significant ongoing electricity costs on top of the build.

Six integrated systems: intense grow lighting sized to the canopy; ventilation and air exchange (exhaust plus intake) to supply fresh air and remove heat and humidity; climate control (AC, and often a dehumidifier) to hold temperature and humidity in range; enough electrical capacity to run it all safely; a way to water and feed the plants; and a prepared room that's sealed, insulated, reflective, and moisture-protected. Higher-end grows add CO2, automated controllers, and monitoring. They all have to work together to keep the environment stable.

A lot — the lights are the dominant load, with AC and dehumidification close behind, all running many hours a day. Because the combined draw is high, a grow room usually needs dedicated circuits and often an electrical panel or service upgrade to run safely; putting grow lights and AC on inadequate wiring risks tripped breakers and fire. That upgrade is a real line item (about $1,500 in the calculator) and should be done by a licensed electrician. Budget for the ongoing power bill too, not just the build.

LED is the modern default: far more efficient (lower power bills), much less heat (so less AC load), long lifespan, and tunable full spectrum — at a higher upfront price. HPS/MH costs less to buy and has a long horticultural track record, but it's less efficient, runs hot (raising cooling costs), and the bulbs need periodic replacement. Over time, LED's energy and cooling savings usually offset its purchase premium, which is why most new setups go LED. The calculator lets you compare HPS/MH, standard LED, and premium full-spectrum LED.

Because even great lighting fails without a stable environment. Grow lights add heat and plants add humidity, so without adequate AC, exhaust, and often dehumidification, the room overheats, humidity spikes, and mold, mildew, and pests move in — the fastest way to lose a crop. Good airflow from oscillating fans prevents the still, humid pockets where mold thrives. Temperature and humidity control directly drive plant health, yield, and quality, which is why the climate systems are a major share of both the cost and the electrical load.

All are commonly converted. A closet or grow tent is smallest and cheapest but needs careful heat and exhaust management in a tight space. A spare room is straightforward to seal and equip. A basement is often ideal — naturally cool and stable (less cooling needed) — but tends to be humid, so plan for strong dehumidification. A garage gives space but swings hot and cold with the seasons, so it needs the most robust climate control and insulation. Every conversion needs sealing, reflective walls, ventilation, climate control, and adequate electrical.

Size it to the canopy you can properly light, cool, and power — not to the space you happen to have. Each plant needs room for light coverage and airflow; crowding invites mold and pests. Your lights cover a set footprint at the right intensity, so match the room to that, and remember a bigger room multiplies cooling, dehumidification, and electrical demand. Leave working space to tend plants and place equipment. Beginners are usually better starting smaller and scaling up, and any local plant-count limits may cap how large you should build.

Ongoing electricity is the defining recurring cost, driven mostly by the lights and the AC/dehumidifier that fight the lights' heat. The monthly bill scales with room size, lighting wattage, hours of operation, climate equipment, and your local electricity rate — it can be substantial for a serious grow. Efficient LED lighting cuts both the lighting draw and the heat (and therefore the cooling load), which is the single biggest lever for lowering operating cost. Factor the power bill into your budget alongside the build.

Anywhere from a day to a few weeks. A closet grow or a tent with a light, fan, and basic supplies is largely plug-and-play in a day or a weekend. A standard room conversion — sealing, reflective walls, lighting, ventilation, climate, and electrical — usually takes several days to a couple of weeks. A professional or commercial build with high-output lighting, automated climate, CO2, and a service upgrade can run a few weeks or more, especially when a licensed electrician, HVAC install, and permits are involved. Much of the time is infrastructure, not the lights.

The electrical and any construction work often require permits and inspections — an electrical panel or service upgrade almost always does, and a licensed electrician typically handles it. Separately, what you're legally allowed to grow, and in what quantity, varies widely by location and is entirely up to local and state law. Confirm both the building-code requirements for your electrical and climate work and the legal rules for your intended grow before you invest in a build. This calculator estimates setup cost only.