Grow Lights: LED vs HPS vs MH for Indoor Gardens in 2026

Indoor grow light technology has moved fast in the past five years. LED was the underdog a decade ago, the upstart five years ago, and now dominates new installations. HPS and MH (high pressure sodium and metal halide, the two main HID technologies) still ship in volume but lose market share each year. This article walks through what each technology actually delivers in watts of usable light per watt of electricity, where it makes sense, and where it falls short. The numbers below assume current-generation hardware, not the cheap Amazon panels that misrepresent specs.

How grow light efficiency is measured

The relevant metric for plants is PPF (photosynthetic photon flux), measured in micromoles per second (umol/s), and efficacy in micromoles per joule (umol/J). PPF measures how many photons in the 400 to 700 nm photosynthetically active range the lamp emits per second. Efficacy normalizes that against electrical input wattage. Higher is better.

Lumens, watts, and Kelvin temperature are largely irrelevant for plant lighting. Lumens measure human visual brightness, which is weighted toward green light that plants barely use. A grower who shops on lumens or pure wattage will pay more for less plant-usable light.

The 2026 benchmark numbers are roughly:

• Top tier LED panels (Samsung LM301H EVO, Mean Well drivers): 2.8 to 3.1 umol/J
• Mid tier LED panels (decent brands, mixed diodes): 2.2 to 2.6 umol/J
• Budget LED panels (no-name Amazon): 1.0 to 1.8 umol/J (often misrepresented)
• HPS double-ended bulbs (current gen): 1.7 to 2.0 umol/J
• HPS single-ended bulbs: 1.4 to 1.7 umol/J
• MH bulbs: 1.5 to 1.8 umol/J
• T5 fluorescent: 1.0 to 1.4 umol/J

The LED efficacy gap over HPS is real and meaningful. A 600 W LED at 2.9 umol/J delivers 1740 umol/s. A 600 W HPS at 1.9 umol/J delivers 1140 umol/s. The same wattage gives 50 percent more usable light from LED.

Heat and the cooling tax

HPS and MH dump 60 to 70 percent of input wattage as heat. A 600 W HPS bulb produces about 400 W of heat. In a small grow tent, that heat needs to leave through ventilation or air conditioning, and it always raises the canopy temperature 10 to 20 F above ambient.

LED panels run cooler, dumping 40 to 50 percent of input wattage as heat. A 600 W LED produces about 250 W of heat. The canopy temperature rises 5 to 10 F above ambient with similar ventilation.

The cooling cost difference is material. A grower running 600 W of HID in a 4 by 4 ft tent in summer typically needs a portable AC unit ($300 to $500 plus $30 to $80 per month in electricity). An LED grower can often manage with just an inline fan and a passive air intake. Over the life of the equipment, the HID cooling cost can add up to more than the LED upgrade premium.

Spectrum and growth phase

HPS spectrum is heavily weighted toward yellow and red wavelengths (2000 to 2200 K equivalent). The spectrum suits flowering and fruiting plants. HPS-only setups produce good bloom yields but weak vegetative growth, with stretched stems and pale leaves.

MH spectrum is blue-shifted (4000 to 6500 K equivalent). It suits vegetative growth with compact stems and dark green leaves. MH-only setups produce strong veg but weak bloom.

Switchable HID setups run an MH bulb in veg, switch to HPS in bloom, and capture both spectrums. The hardware is a $200 to $400 ballast plus the two bulbs.

LED panels cover full spectrum with white diodes (which contain blue, green, and red components) supplemented by red diodes (660 nm) and occasionally far red (730 nm) and UV. A quality full spectrum LED grows from seed to harvest on a single panel without bulb swaps.

Lifespan and replacement cost

LED panels have a rated lifespan of 50,000 to 60,000 hours of useful life. At 18 hours per day, that is 7 to 9 years. The diodes degrade slowly over that time, losing roughly 30 percent of output by the end of useful life. Failure modes are usually driver electronics, not diodes.

HPS bulbs have a rated lifespan of 20,000 to 24,000 hours, but PAR output degrades by 25 percent within 5000 hours and 50 percent by 10,000 hours. In practice growers replace bulbs every 1 to 2 grow cycles (about 1 year) to maintain output. Each replacement costs $40 to $80 per bulb.

MH bulbs follow similar degradation: 1 to 2 grow cycles per bulb, $40 to $70 per replacement.

Over a 7 year period, the LED grower replaces nothing (or one panel if a driver fails). The HPS or MH grower replaces 6 to 8 bulbs at $300 to $500 total in replacement cost.

Initial cost

A 600 W LED panel from a reputable brand costs $400 to $700. The price has dropped 30 to 40 percent in the past three years.

A 600 W HPS kit (ballast, bulb, reflector) costs $200 to $300 new.

A 600 W MH bulb alone costs $40 to $70, sharing a ballast with HPS if running a switchable kit.

LED has higher upfront cost but lower running cost. Break-even on electricity savings (60 to 100 W lower wattage for equivalent PPF) and bulb replacement savings typically happens within 12 to 24 months for daily use.

Which technology for which grow

Choose LED if you want the lowest running cost, cooler grow space, longest equipment life, and you can stomach the upfront premium. LED suits 90 percent of new home installations.

Choose HID (HPS plus MH) if you have a tight upfront budget, a cool grow space where waste heat is acceptable or wanted (cold basement), and you do not mind replacing bulbs annually. HID still suits some larger commercial setups where the per-watt cost difference matters at scale.

Choose T5 fluorescent only for seedlings, clones, and microgreens. T5 lacks the intensity for vegetative or flowering growth on a serious scale but works well close to the canopy for low-light crops.

See the methodology page for our grow light testing protocol. Light is one input among several; pair this article with our indoor tent sizing guide and our hydroponic systems comparison.

Frequently asked questions