Jumping into indoor hydroponics? One of the most critical things to get right is your lighting. Without sunlight, your plants are counting on you to provide the perfect artificial light, so you’ve got to know how much they need, which lights to use, and how to manage power and safety.
How Much Light Do Your Plants Really Need?
Plants use light for photosynthesis—basically, it’s their energy smoothie. But not all plants need the same amount of light. To figure out what your plants need indoors, we measure light intensity using KLux (kilolux) or PAR (Photosynthetically Active Radiation). These help you know how much light is actually hitting your plants and how much they can use for growth.
The amount of light depends on the plant type and its growth stage. For example, leafy greens like lettuce are pretty chill with lower light levels, while heavy hitters like tomatoes or peppers need more.
Its a good idea to buy yourself a meter so you can measure what your plants are getting, but you don't need to break the bank, this one [US] [CA] will do just fine.
Light Requirements by Plant Type
Here’s a quick guide for light intensity (in KLux) for some common hydroponic plants, we'll demonstrate calculating which and how many lights to buy below:
Plant | Light Intensity (KLux) | Recommended Light Hours (Per Day) |
Lettuce | 10–15 KLux | 12–14 hours |
Tomatoes | 25–30 KLux | 12–16 hours |
Cannabis (Veg) | 25–40 KLux | 16–18 hours |
Cannabis (Flower) | 40–60+ KLux | 12 hours (photoperiod) |
Herbs | 15–20 KLux | 12–14 hours |
Peppers | 25–30 KLux | 12–16 hours |
Spinach | 15–20 KLux | 12–14 hours |
Strawberries | 20–25 KLux | 12–16 hours |
Cucumbers | 25–30 KLux | 12–16 hours |
Duration matters. Some plants (like cannabis) need specific light cycles to trigger flowering, while others, like tomatoes, can bask in the light for longer hours without complaining, but careful with lettuce and spinach - too much light causes them to pre-maturely bolt.
If you want the specifics for a plant, try asking our AI GPT for details.
Light Needs for Different Growth Stages
Your plants go through phases—just like we do—and their light needs change as they grow:
Seedling Stage: Go easy with the light. Around 10–15 KLux for 14–18 hours a day.
Vegetative Stage: Time to bump it up. Aim for 25–40 KLux.
Flowering Stage: Crank up the intensity to 40+ KLux, if your growing photoperiod-sensitive plants like Cannabis, drop the light to 12-hour cycles.
Matching the right amount of light at the right time helps prevent weak, leggy plants and sets them up for success as they mature. If your lights don't have dimmers you can adjust the intensity by raising and lowering them.
Types of Grow Lights: Which Should You Choose?
LEDs, HPS, CFL… so many choices! But here’s the deal: LEDs are usually your best bet for home hydroponics. Let’s break it down:
LED Grow Lights: These are your go-to. They’re energy-efficient, don’t turn your grow room into a sauna, and come in full-spectrum options to support all stages of plant growth. Plus, they last forever (almost).
HPS (High-Pressure Sodium): High power but lots of heat. These are more for commercial setups since you’ll need extra ventilation, reflectors, and other gear.
CFL (Compact Fluorescent Lights): Cheap and easy but not powerful enough for much more than seedlings or herbs.
If you’re just starting or keeping things small, LEDs are the way to go. They save you money, produce less heat, and are simple to use.
Understanding Light Spectrum: Full Spectrum vs. Veg Modes
Grow lights come in different flavors—full spectrum or lights with specific modes. Here’s the breakdown:
Full Spectrum: Mimics natural sunlight, covering all your plant’s needs from seedling to harvest.
Vegetative Mode (blue-heavy): Best for leafy growth.
Flowering Mode (red-heavy): Great for flowers and fruit.
If you’re keeping it simple, go with full spectrum. But if you want total control, lights with separate veg and flower modes let you dial things in.
So... How many watts / lights do I need to grow X plant?
Without actually owning lights to measure, it can be tricky to figure out how much lighting you’ll actually need to grow a specific plant. I’ve put together a guide to give you an idea of how many watts (using true power draw for LED lights) you’ll typically need to grow different plants indoors.
When you’re shopping for LED lights, be aware that many brands advertise the wattage as HPS equivalent. This can be misleading, as it’s often around 10x higher than the actual power draw. For example, a light labeled as "1000W" may only draw 100 watts of true power. Always check the actual power draw in the specifications so you’re not buying something underpowered for your needs.
Let’s break it down:
Plant Type | Light Intensity (KLux) | Recommended Wattage (True Power Draw) | Coverage Area |
Lettuce | 10–15 KLux | 25–35 watts per square foot | 2x2 ft = ~100 watts |
Tomatoes | 25–30 KLux | 40–50 watts per square foot | 2x2 ft = ~150-200 watts |
Cannabis (Veg) | 25–40 KLux | 30–40 watts per square foot | 2x2 ft = ~120-150 watts |
Cannabis (Flower) | 40–60+ KLux | 50+ watts per square foot | 2x2 ft = ~200+ watts |
Herbs (Basil, Cilantro) | 15–20 KLux | 25–30 watts per square foot | 2x2 ft = ~100-120 watts |
Peppers | 25–30 KLux | 40–50 watts per square foot | 2x2 ft = ~150-200 watts |
How to Calculate Your Lighting Needs
To figure out how much wattage you need, you’ll first want to know the coverage area your light will need to support. Most LEDs list their recommended coverage area in their product details (often as 2x2 ft or 4x4 ft).
Here’s a simple formula to help:
Calculate Your Grow Space Area:
Multiply the length by the width of your grow space. For example, a 3x3 ft tent = 9 sq. ft.
Multiply by the Recommended Wattage Per Square Foot:
For lettuce, you’d need around 30 watts per square foot. So for a 3x3 ft space:
9 sq. ft. x 30 watts = 270 watts of true power draw.
Double-Check Coverage Areas:
If the LED light you’re considering says it covers 2x2 ft, you’d need more than one for larger areas like a 3x3 ft or 4x4 ft space. Plan accordingly!
When you're looking at our pictures, all of our lights are on the weaker side (60 Watts) with the exception of Cannabis (either 2x60W or 2x100W), I wouldn't suggest doing less then us.
How Much Do Grow Lights Cost?
Buying grow lights isn’t just about the upfront cost—you’ve also got to think about long-term energy use and how well they’ll suit your plants and space.
Entry-Level LEDs run between $60–$150 and are perfect for smaller setups or low-light plants like lettuce and herbs. They’re energy-efficient (usually pulling around 100 watts of true power).
Mid-Range LEDs (200+ watts) cost more, usually around $250–$500, but they pack a punch. With higher light intensity, better spectrum quality, and coverage for larger areas, these are made for serious growers. If you’re growing tomatoes, peppers, or cannabis, these lights provide the intensity and control you need for consistent, thriving plants.
Mars Hydro [US] [CA] and Spider Farmer [US] [CA] are quality lights, but if you're on a really tight budget, search for misc brands that use Meanwell power supplies and Samsung diodes.
Heads up, with most lights you'll have to get your DIY on, while they do come with ratchet ropes to adjust height, you'll have to hang them from something, we'll do a post with some options coming up.
If you're looking for a light with a stand, we've heard decent things about this one [US] [CA], however keep in mind that it's use would be limited to herbs & greens as you'll need a little more juice for bigger stuff.
💡Pro Tip: Always check the true power draw of your LED lights—not just the advertised wattage (often listed as an HPS equivalent).
Power Usage and Electrical Requirements
Grow lights can be power-hungry, so make sure your home can handle the load. Most household circuits are 15 amps, which can handle about 1,800 watts—but to be safe, stick to around 1,440 watts per circuit. Do the math before plugging everything in!
Using Smart Plugs for Light Automation
Need to manage light cycles? If your lights don’t have built-in timers, grab a cheap smart plug like the Sonoff S31. These bad boys let you automate your light schedule, keeping your plants on track without you having to remember when to turn the lights on and off.
Protect Your Eyes: Light Safety Tips
Grow lights can be tough on your eyes. If you’re spending a lot of time around high-powered LEDs, protect your peepers!
Keep grow lights below eye level if they’re in a shared space.
Use lower-wattage lights if the setup is in a room you’re in often, keep them closer (lower) to your plants.
Conclusion: Light Up Your Grow Room the Right Way
Lighting is one of the most important steps to indoor growing success. Choose the right lights, give your plants the right intensity, and manage power wisely. Get your lighting dialed in, and you’ll be well on your way to thriving plants.
Need help managing nutrients or tracking your grow? The Kanana Gardens App is here to help you keep everything in check. It’s free for household use and available on the Apple Store and Google Play in US & Canada, along with Web for everywhere else.