Grow Light Lamps
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Grow lamps are consumables. Unlike an LED fixture, an HPS or MH lamp degrades from the day you switch it on – output falls steadily while the wattage draw stays the same. A lamp at eighteen months is costing you the same electricity for meaningfully less light.
When to replace
| Lamp type | Replace after |
|---|---|
| Single-ended HPS | Roughly 12 months, or 2-3 cycles |
| Double-ended (DE) HPS | Roughly 18 months - slower degradation |
| Metal halide | Roughly 12 months |
| CDM / CMH | Up to 2 years - the longest lived |
A lamp that still lights is not a lamp that still works. If it has done two full cycles, replacing it is usually cheaper than the yield you lose by not replacing it.
Which spectrum
- HPS – red-heavy, the flowering standard for decades. Still the cheapest route to serious output.
- Metal halide – blue-heavy, for vegetative growth. Keeps plants compact rather than stretching. See MH lamps.
- Dual spectrum – a compromise that runs the whole cycle on one lamp. Convenient rather than optimal.
- CDM / CMH – ceramic discharge, a fuller and more natural spectrum with better colour rendering and long life. See 315W CDM lamps.
Check the fitting before you order
Single-ended lamps use an E40 screw fitting; double-ended use a K12x30 and need a DE reflector and a 400V ballast. They are not interchangeable. CDM uses PGZ18 or E40 depending on wattage. If you are unsure, tell us your ballast and reflector and we will match it – see ballasts and reflectors.
Handling
Never touch the glass with bare fingers – skin oil creates a hot spot and shortens lamp life or cracks the envelope. Use a cloth or gloves, and let a lamp cool fully before removing it.
Related
See HPS grow lights, all grow room lights, and LED grow lights if you are considering moving away from lamps entirely.
Why buy lamps from The Hydro Bros?
We are a hydroponics shop in Croydon with fresh stock rather than lamps that have sat in a warehouse for two years. Tell us your ballast and we will match the lamp. Discreet UK and European delivery, and excellent customer reviews on Trustpilot.
