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Description
cmh grow light bulb Growers Choice Horticultural Lighting 315W SE CMH Complete Fixture 3KGrower's Choice 315W CMH Grow Light Happy Hydro Full spectrum light that actually matches sunlight, at 315 watts The Grower's Choice GC 315 is a complete ceramic metal halide fixture with a built in digital ballast, open reflector, and your choice of lamp spectrum. CMH produces a broader, more balanced spectrum than HPS with a CRI up to 97, which means your plants see light closer to what they'd get outdoors. The fixture runs 120V 240V, dims without
Full-spectrum light that actually matches sunlight, at 315 watts
The Grower's Choice GC-315 is a complete ceramic metal halide fixture with a built-in digital ballast, open reflector, and your choice of lamp spectrum. CMH produces a broader, more balanced spectrum than HPS with a CRI up to 97, which means your plants see light closer to what they'd get outdoors. The fixture runs 120V/240V, dims without external controllers, and includes full circuit protection so you're not replacing ballasts after a power surge.
3-year warranty
120V/240V compatible
Controller compatible
Side by side
315W CMH vs. a standard 600W HPS
600W HPS
- Narrow spectrum, heavy in yellow/orange, almost no UV or blue
- 600W draw plus additional cooling costs
- Separate ballast, reflector, socket, and lamp to assemble
- Magnetic ballasts hum, flicker, and lose efficiency over time
- Bulbs degrade quickly, typically need replacement every 6 to 9 months
- No built-in dimming or fault protection
GC-315 CMH
- Full spectrum with UV, blue, red, and far-red, CRI up to 97
- 315W draw, nearly half the power for competitive PAR output
- All-in-one fixture: ballast, reflector, and lamp in one unit
- Digital square-wave ballast, no hum, no flicker, consistent output
- 15,000-hour rated lamp life, roughly double a standard HPS bulb
- Built-in dimming dial and full circuit protection against surges
What makes it different
Built for real grow rooms, not spec sheets
Closest spectrum to sunlight available in HID CRI up to 97
The 4K lamp scores a 97 CRI, meaning its spectral output is nearly identical to natural daylight. The 3K lamp sits at CRI 90 with enhanced red for flowering. Plants respond to this broader spectrum with tighter internodal spacing and more uniform growth.
Low-frequency square wave ballast
The digital ballast drives the lamp with a low-frequency square wave, which is up to 30% more efficient than magnetic ballasts and maintains that efficiency for the life of the unit. No internal fans needed because the case design acts as a passive heat sink.
Full circuit protection with 3-second self-test
On every ignition, the ballast runs a 3-second diagnostic. It protects against open circuit, short circuit, over-voltage, under-voltage, and over-temperature faults. If something is wrong, the ballast enters protection mode instead of damaging itself or the lamp.
Dimmable with Smart Step and Super Lumen modes
Turn the dial to reduce output when plants are young or temperatures are high. Super Lumen pushes the lamp past rated wattage for maximum PAR when you need peak intensity during late flower.
Runs cooler than HPS at comparable PAR
At 315W, this fixture produces significantly less radiant heat than a 600W HPS. In small tents or rooms without dedicated HVAC, that can be the difference between manageable temperatures and constant heat stress.
Compatible with Grower's Choice Master Controller
Daisy-chain up to 100 fixtures per zone using the optional Master Lighting Controller. Supports timed on/off, sunrise/sunset ramping, and dual thermal probe auto-dim shutdown for commercial setups.
Specs
Technical specifications
Wattage
315W
Input voltage
120V / 240V (50/60 Hz)
PAR output (3K lamp)
570 µmol/s initial
Coverage area
3' x 3' flower, 3.5' x 3.5' veg
Lamp life
15,000 hours rated
Input current
2.9A @ 120V, 1.5A @ 240V
Power factor
> 0.98
Warranty
3 years (Grower's Choice)
Setting up your GC-315
1
Hang the fixture
Use the included hanging hardware to mount the fixture from your tent crossbars or ceiling hooks. Adjust height to 18 to 24 inches above the canopy for flowering, 24 to 30 inches for veg.
2
Install the lamp
Insert the 315W CMH lamp into the built-in socket. The lamp seats horizontally in the open reflector. Handle by the base only, not the glass envelope.
3
Set the power level
Turn the ballast dial to your preferred output. Start lower for seedlings or clones, then step up to full power as plants mature. Use Super Lumen mode during peak flower if temperatures allow.
4
Plug in and grow
Connect to any standard 120V outlet (ships with a 120V plug). For 240V operation, swap the cord end or hardwire. The ballast auto-detects frequency and adjusts output to prevent flicker.
In the box
Everything you need to start growing
Included with every fixture
- GC-315W all-in-one fixture with integrated digital ballast
- One 315W CMH lamp (your choice of spectrum)
- Open reflector with horizontal lamp mount
- 120V power cord (pre-attached)
- Hanging hardware
- 3-year manufacturer warranty
Lamp options
- 3K-R (3,100K): Full spectrum optimized for bloom, enhanced red, CRI 90, 570 µmol/s
- 4K (4,200K): Veg-optimized with heavy blue output, CRI 97, promotes tight internodal spacing
- 10K MH Finishing: Metal halide finishing lamp for the final 2 weeks, boosts resin and aroma
- No Bulb: Fixture only, bring your own 315W SE CMH lamp
Not sure which lamp to pick? The 3K-R is the most popular choice for growers who want one lamp for the full cycle. If you run separate veg and flower spaces, pair the 4K for veg with the 3K-R for flower. Call or email us: 716-217-0353 / [email protected]
Questions
Frequently asked questions
The GC-315 flowers a 3x3 area effectively and vegs a 3.5x3.5 area. In a 4x4 tent, you'll get solid growth in the center but the corners will be noticeably dimmer. For full 4x4 coverage in flower, most growers either run two 315W fixtures or step up to a 630W CMH or LED. If you're growing one or two large plants in the center of a 4x4, a single 315W can work fine.
LEDs in this price range typically pull similar wattage but produce a narrower, diode-driven spectrum. CMH's advantage is spectral quality: the broad, continuous spectrum is closer to sunlight than the peaked spectrum of most LEDs. Many growers report visibly healthier plants and tighter structure under CMH compared to budget LEDs. The trade-off is that CMH generates more heat and the lamp needs replacement every 15,000 hours. If heat is your main concern, LED may be the better fit. If spectrum quality matters more, CMH wins at this price.
Grower's Choice rates their CMH lamps at 15,000 hours. Running 18 hours per day in veg, that is roughly 2.3 years. Running 12 hours per day in flower, that is about 3.4 years. Spectrum and output do degrade over time, so many growers swap lamps every 12 to 18 months for peak performance. Replacement lamps are available separately on our site.
The ballast accepts both 120V and 240V input. It ships with a 120V plug. To run on 240V, you'll need to swap the plug or hardwire to a 240V circuit. Running on 240V draws less current (1.5A vs 2.9A), which is better if you're running multiple fixtures on the same breaker. The fixture auto-adjusts, no switch or setting needed.
Yes, any standard single-ended 315W CMH lamp with a PGZ18 base will fit. Grower's Choice lamps are optimized for this ballast's frequency and output, so using their lamps ensures the best spectral performance and longest lamp life. Third-party lamps will work but may not perform identically.
Not for a single fixture. A standard appliance timer handles on/off scheduling, and the built-in dial controls dimming. The optional Grower's Choice Master Lighting Controller becomes useful when you're running multiple fixtures and want centralized sunrise/sunset ramping, thermal monitoring, and auto-dim shutdown. We carry the controller separately if you need it later.
If you receive a defective or damaged unit, email us a photo at [email protected] and we'll make it right immediately: replacement or refund, your call. For change-of-mind returns, we accept returns within 30 days for items in new, resalable condition. If you're not sure whether this product is right for your setup, call us first at 716-217-0353. We'd rather answer your questions before you order.
Happy Hydro has been selling growing equipment since 2006. We've carried Grower's Choice for years because the systems work great and customers who buy them leave happy. Have questions before you order? Call 716-217-0353 or email [email protected]. We're easy to reach and happy to help!
Questions? We're easy to reach.
Happy Hydro has been serving growers since 2006. Call or email us before you order, after you order, or any time something comes up. When you're happy, we're happy.
Shipping Notes
- Free Standard Shipping on $100+ Orders to the USA.
- Except Preorder products are shipped in 48 hours.
- Delivery to the USA:
- Standard Shipping : 3-10 business days
- If time is of the essence, please consider selecting expedited delivery for faster service.
Exchange/Return Notes
- We offer a 30-day return/exchange service after receiving.
- Final sale items are not eligible for returns or exchanges.
- To process your return/exchange, please contact us at [email protected]
- Please click here for more details>>> Return & Exchange Policy
4.5 ★★★★★
Based on 11 reviews
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Product Reviews
★★★★★ 5
Spoiler-free Review - The Martian Dialed Up To 11
Format: Kindle
If you loved the Martian in either book or movie form, Project Hail Mary will likely delight you.
The main character (who I'll leave nameless to avoid spoilers) is nearly identical to The Martian's lead, Mark Watney. They have similar personalities, the same fundamental mission of surviving in a hostile environment, and both use real-world biology, chemistry, and physics to solve their problems from start to finish. The book provides an early test for whether or not you'll enjoy it: on page five, when our protagonist is being quizzed by an annoyingly paternalistic computer that is demanding to know the cube root of eight, our hero replies with the smart aleck answer: "two times e to the two-i-pi". If you find this interaction amusing, all good; if it's off-putting, turn back now.
In fairness, Project Hail Mary shares The Martian's flaws as well. The protagonist's character is a bit better developed - but only slightly. The conflict is entirely man-vs-environment. And though the protagonist is often in situations that might cause one to ponder the essential truths of the human condition, he never does. His personality and behavior as a sarcastic problem-solving scientist / engineer are pitch-perfect but the book rarely goes any deeper. He has an established motivation and a flaw to be overcome - but these are really just superficial grace-notes (see what I did there?). This is not Crime and Punishment. Instead, it's a page-turning action-hero book - where instead of firing shots, the action hero saves the day by doing science really well. Books that celebrate real science are rare, so if that's what you came for, you're going to love what Project Hail Mary delivers.
Although largely similar, there are four main ways in which Project Hail Mary differs on the Martian so I'll touch on those now:
1. The stakes are higher - much higher! In The Martian, Mark Watney is already a bit of a super hero - he's an astronaut after all - and all he really needs to do is stay alive. In Project Hail Mary, our hero is much more of an every-man and his job is nothing less than to save the human race.
2. The Martian is told in chronological order. In Project Hail Mary, our hero awakens with a serious case of amnesia and can't even remember his own name. He starts his adventures at essentially the most dull part of his recent life. As time passes he both tackles dramatic new challenges and remembers the wild adventures that brought him here. Andy Weir does a fantastic job of interweaving the past and the present and the result is a very effective narrative framework that lands on a "Wow!" moment at the end of nearly every chapter.
3. Project Hail Mary is a buddy story. In The Martian, Mark Watney is alone in his battle against the elements of Mars for nearly the entire book. By contrast, Project Hail Mary, once it really gets going, is absolutely a tale of buddy-bonding. This surprised and, ultimately, delighted me. It helps give the protagonist a bit more of a human side. And the team problem-solving scenes are, again, pitch-perfect.
4. Project Hail Mary puts the 'fiction' back in Science Fiction. In The Martian, leaving aside the opening wind storm and the closing chapter of wish-fulfillment heroics, we are essentially in a very tightly written NASA simulation. I found this incredibly enjoyable - but one could reasonably ask, where are the big ideas? Where are the bold 'what ifs'? The answer is, they're in Project Hail Mary! The science is still real and omni-present, but the fiction is big, bold, and awesome. If you're main draw for the Martian was the NASA lore and you wished Weir would write an even tighter sequel detailing the Apollo 13 events, you may be a bit disappointed - but everyone else is going to love this change of pace!
So that's it in a nutshell: Project Hail Mary is a fantastic next book to read after The Martian. It's a clear spiritual successor but brings new ideas and structure to the game. Enjoy!
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Reviewed in the United States on February 16, 2025
★★★★★ 4
Excellent Hard Sci-Fi… Until the Politics Pull You Out
Format: Kindle
I was really excited to dive into Project Hail Mary. As a longtime Isaac Asimov fan, I’ve been craving fresh, modern hard science fiction that actually respects the science. This book delivered — at least for a while.
The author injects real science into the story in a way that’s both fun and fantastic. You don’t need to be an engineer to follow it; a solid high-school education is plenty. The concepts stretch your imagination without ever feeling impossible, and for the first chunk of the book I was hooked. I genuinely thought I’d found a new favorite author.
Then the jarring interruptions started.
Out of nowhere you get yanked out of the immersive sci-fi world by modern political pandering that feels completely unnecessary. A random parenthetical about Columbus “discovering an already inhabited world” when comparing something to the New World. Casual pronoun lectures. Characters selected or described by race and identity in ways that scream “check the boxes.” These moments don’t serve the story — they feel injected. Once you notice the author’s leanings, it becomes hard to unsee.
Each time it happens, the fantasy evaporates. It takes several chapters to sink back into the story… only for the next micro-lecture to pull you right back out.
Overall, I loved the writing, the hard science, and the imagination. It’s some of the best sci-fi I’ve read in years. I just wish the author had trusted the story instead of sneaking in real-world politics. It’s like eating the best meal of your life… and then finding a hair or two in it.
Strongly recommended for the sci-fi, with the above caveat.
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Reviewed in the United States on May 17, 2026
★★★★★ 5
Engrossing and Thought-Provoking
Format: Hardcover
This is an absolutely engrossing read in the first half of the book, especially--so much so that I actually canceled a social plan so that I could keep reading.
The author shifts effortlessly across scenes and time--the play of past and present is very much part of the book's plot and insight--and I developed a fast curiosity and unsettling investment in understanding our anti-heroine/heroine Natalie. This surprised me, because had a friend not recommended the novel I never would have signed on to spend time in the head of a "tradwife." For me the novel was an imagined and imaginative provocation on American womanhood (and masculinity) in the 21st century, where no options or "performances" seem entirely satisfying or even real. I found it simultaneously disturbing and darkly humorous, especially in its depiction of young women's collegiate lives.
However, readers should have some tolerance for caricature throughout. While I howled at the depictions of the miserable lives of aspiring "modern" women in the dorms and figuratively pounded my fists at the hypocrisy of the tradwife, I was also conscious of hyperbole and exaggeration--no, their lives aren't that bad; nor, I would guess, are the "tradwives" as bad as Natalie, who is a profoundly unlikable character.
I did find that the novel bogged down in its middle and late-middle chapters--the mystery of what's happening to Natalie remains but the momentum seems to stall out into repetition. I also felt that the ending seemed too rushed and too tidy, given the nuance we see earlier in the novel. It ends with what feels like a reductive endorsement of modern (or post-modern) life for women when, earlier in the novel, we get to contemplate the flaws in ALL of the scripts and performances that women--and the hapless Caleb-- are asked to live by, or choose... Indeed, the characters that I would have loved to hear more from are the two who seemed more grounded and, ultimately, perhaps happier than the others: Natalie's sister and even her mother... The concluding exposition felt rushed, as did the analysis, in other words...Some of the religious scenes seemed tone-deaf to me... I'm not an evangelical, but Natalie's relationship to God strained credulity.
**Highly recommend** this to anyone looking for a provocative and engrossing read on women's lives and constraints in the age of social media that engages in a fascinating thought experiment along the way...
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Reviewed in the United States on May 26, 2026
★★★★★ 4
An unexpected reading experience!
Format: Hardcover
Very unexpected novel! I went into it without any knowledge or prior information of what it was going to be about. Main character is not a person you would want to be friends. So when calamities happen to her it was hard for me to muster up much sympathy or compassion. It was more of “you had this coming, you deserve every miserable minute”. And boy, there were many! Some harder to believe than others. As I was reading, I first thought- I don’t want to keep this book, it’s not worth saving. But it developed to be definitely the type of story that sticks in your mind, you find yourself revisiting parts and characters and wondering why that happened and why did that person react a certain way. And to me that’s a book worth reading and keeping on my limited bookshelf. So I changed my opinion as I read to the end of the novel. It is certainly a book worthy of a neighborhood book group discussion. I am recommending and sharing my copy to family members and reading friends.
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Reviewed in the United States on May 20, 2026
★★★★★ 5
Beneath the perfect surface
Format: Kindle
Yesteryear completely caught me off guard in the best possible way. What begins as a fascinating look into social media influence, curated perfection, and historical living slowly unfolds into something far deeper and far more emotional than I expected.
The storytelling was incredibly well done, especially the way the author balanced the polished modern influencer world against the harsh realities of 1800s frontier life. The transitions between timelines and perspectives were seamless, and by the end, every piece fit together in a way that completely redefined the story.
What made this especially compelling for me was how layered Natalie’s character felt. Her upbringing, family expectations, faith, public image, and the pressure to maintain perfection all shaped the choices she made throughout the story. Rather than feeling one-dimensional, she felt like someone slowly buckling under the weight of everything she believed she was supposed to be.
The emotional impact of this book surprised me. Beneath the historical elements and social media commentary is a story about identity, appearances, family, and the toll that constant performance can take on a person and those around them.
This is one of those books where the less you know going in, the better the experience will be. I expected an entertaining premise, but I ended up with a story that lingered long after I finished the final page.
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Reviewed in the United States on May 28, 2026