Grow Light Bulbs
Browse our extensive range of replacement grow light bulbs, covering HPS, MH, and CDM technology from trusted manufacturers including DLI, DimLux, LUMii, Osram, Philips, Sunmaster, and Sylvania. Whether you need a direct replacement for an existing fixture or want to upgrade your spectrum for better flowering results, our bulb range covers every common wattage and fitting used in UK grow rooms.
Finding the right replacement bulb
The most important factor when replacing a grow light bulb is matching both wattage and lamp type (HPS, MH, or CDM) to your existing ballast — running a bulb rated for a different wattage than your ballast can cause inefficient light output or premature bulb failure. Most of our bulbs use the standard E40 fitting common across UK HID fixtures, though always check your specific fixture's requirements before ordering.
Dual-spectrum vs single-spectrum bulbs
Many of our HPS bulbs — like the Sunmaster Dual Spectrum and LUMii SunBlaster ranges — are "dual spectrum," blending red and blue wavelengths to support both vegetative and flowering growth from a single bulb. Single-spectrum bulbs are typically optimised heavily toward one stage, usually flowering, and paired with a separate MH or CDM bulb for vegetative growth.
Single-ended vs double-ended (DE) bulbs
Double-ended bulbs, held at both ends within the fixture, generally deliver more even light distribution and slightly higher output efficiency than single-ended equivalents at the same wattage — but require a DE-specific fixture and ballast, so they're not interchangeable with standard single-ended setups.
When to replace your bulb
Even if a bulb still lights up, its usable spectrum and intensity degrade well before visible failure. Most manufacturers recommend replacing HPS and MH bulbs every 9-12 months of regular use (roughly one grow season for many home growers) to maintain optimal yield.
FAQ
How do I know what wattage bulb I need?
Check your ballast's rated output — it will specify a wattage (e.g. 600W) or a dimmable range (e.g. 250W-660W). Always match your bulb to a wattage your ballast supports.
Can I use an HPS bulb in an MH ballast, or vice versa?
No — HPS and MH bulbs require different ballast types due to different ignition voltages and operating characteristics. Using the wrong bulb/ballast combination can damage both.
Do more expensive bulbs actually perform better?
Generally yes — premium bulbs from established manufacturers typically offer higher lumen/PAR output, more stable spectrum over their lifespan, and longer usable life before requiring replacement, compared to budget alternatives.