# Are metal halide and High Pressure Sodium bulbs interchangeable? **URL:** \ **Category:** Factual Questions\ **Created:** [February 3, 2015, 6:37pm UTC](https://boards.straightdope.com/t/are-metal-halide-and-high-pressure-sodium-bulbs-interchangeable/711741 "2015-02-03T18:37:39Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![aceplace57](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aceplace57/32/3500_2.png) [@aceplace57](https://boards.straightdope.com/u/aceplace57)\ **Post date:** [February 3, 2015, 6:37pm UTC](https://boards.straightdope.com/t/are-metal-halide-and-high-pressure-sodium-bulbs-interchangeable/711741/1 "2015-02-03T18:37:39Z")
I switched out my front and back porch lights with a 50W High Pressure Sodium fixture (this was in 2003). Link to the GE bulb that came with the fixture. > **[GE 11345 - LU50 - HPS - 50W - ANSI S68 | 1000Bulbs.com](https://www.1000bulbs.com/product/2428/LU0050-0003.html)** > > Shop GE 11345 - LU50 - HPS - 50 Watt - Lucalox - High Pressure Sodium - ANSI S68 - Medium Base - LU50/MED/ECO at 1000Bulbs.com today. A friend has a couple 100W metal halide ED17. here it is. > **[Philips 429968 - 100W Metal Halide Bulb | 1000Bulbs.com](https://www.1000bulbs.com/product/115281/PHILIPS-429968.html)** > > Shop for Philips 429968 100W ED17 Pulse Start 4000K Metal Halide bulbs. LOW prices and FAST shipping on Philips metal halide bulbs now at 1000Bulbs.com! the metal halide says its a pulse start the High Pressure Sodium doesn’t list a start method any chance these are interchangeable? how about the wattage difference? My buddy has no use for the metal halides and would give them to me. ---
**Author:** ![boytyperanma](https://avatars.discourse-cdn.com/v4/letter/b/4491bb/32.png) [@boytyperanma](https://boards.straightdope.com/u/boytyperanma)\ **Post date:** [February 3, 2015, 6:50pm UTC](https://boards.straightdope.com/t/are-metal-halide-and-high-pressure-sodium-bulbs-interchangeable/711741/2 "2015-02-03T18:50:14Z")
No they are not. The fixture has a transformer to power the lamps with the appropriate voltage. Metal halide and high pressure sodium operate at different voltages. ---
**Author:** ![aceplace57](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aceplace57/32/3500_2.png) [@aceplace57](https://boards.straightdope.com/u/aceplace57)\ **Post date:** [February 3, 2015, 6:59pm UTC](https://boards.straightdope.com/t/are-metal-halide-and-high-pressure-sodium-bulbs-interchangeable/711741/3 "2015-02-03T18:59:32Z")
ok. well it would be nice. I could get a metal halide fixture. But they are **expensive**. Quite a bit more than I paid for my High Pressure Sodium fixture. not even sure this would work. Its metal halide 100 W not ED17 Geez thats expensive. Even with my trade discount it would be over $160 > **[4000K, 8,100 lm, Wall Pack](https://www.grainger.com/product/LUMAPRO-Wall-Pack-4000K-23Y144?s_pp=false&picUrl=%2F%2Fstatic.grainger.com%2Frp%2Fs%2Fis%2Fimage%2FGrainger%2F23Y144_AS01%3F%24smthumb%24)** > > Looking for 4000K, Wall Pack? Find it at Grainger.com®. With over 1.6M products and 24/7 customer service we have supplies and solutions for every industry. ---
**Author:** ![Jackmannii](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jackmannii/32/311_2.png) [@Jackmannii](https://boards.straightdope.com/u/Jackmannii)\ **Post date:** [February 4, 2015, 1:59pm UTC](https://boards.straightdope.com/t/are-metal-halide-and-high-pressure-sodium-bulbs-interchangeable/711741/4 "2015-02-04T13:59:45Z")
This is not strictly applicable to the OP’s situation, but there are [conversion bulbs](https://www.1000bulbs.com/category/conversion-grow-bulbs/) for sale that are supposed to allow you to use an HPS bulb in a MH fixture and vice versa - and also switchable ballasts that permit usage of both types of bulbs in one fixture. ---
**Author:** ![kayaker](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kayaker/32/441_2.png) [@kayaker](https://boards.straightdope.com/u/kayaker)\ **Post date:** [February 4, 2015, 4:11pm UTC](https://boards.straightdope.com/t/are-metal-halide-and-high-pressure-sodium-bulbs-interchangeable/711741/5 "2015-02-04T16:11:41Z")
Metal halide for vegetative growth, high pressure sodium for flowering. 😉 ---
**Author:** ![heartsplayer](https://avatars.discourse-cdn.com/v4/letter/h/d9b06d/32.png) [@heartsplayer](https://boards.straightdope.com/u/heartsplayer)\ **Post date:** [September 17, 2016, 10:05pm UTC](https://boards.straightdope.com/t/are-metal-halide-and-high-pressure-sodium-bulbs-interchangeable/711741/6 "2016-09-17T22:05:48Z")
> [@aceplace57](#): > > I switched out my front and back porch lights with a 50W High Pressure Sodium fixture (this was in 2003). > Link to the GE bulb that came with the fixture. > [https://www.1000bulbs.com/product/2428/LU0050-0003.html](https://www.1000bulbs.com/product/2428/LU0050-0003.html) > > A friend has a couple 100W metal halide ED17. here it is. > [https://www.1000bulbs.com/product/115281/PHILIPS-429968.html](https://www.1000bulbs.com/product/115281/PHILIPS-429968.html) > > the metal halide says its a pulse start > > the High Pressure Sodium doesn’t list a start method > > any chance these are interchangeable? how about the wattage difference? > > My buddy has no use for the metal halides and would give them to me. I don’t know the ins and outs of these systems but it would likely be best to keep to HPS bulbs in HPS fittings. I have seen a video before of someone using a 250W Metal halide bulb in a Mercury Vapor streetlight, but don’t know about HPS to Metal Halide. And if the worst comes to the worst, you can just sell the metal halide bulbs online anyway. 😛 ---
**Author:** ![Mdcastle](https://avatars.discourse-cdn.com/v4/letter/m/958977/32.png) [@Mdcastle](https://boards.straightdope.com/u/Mdcastle)\ **Post date:** [September 18, 2016, 3:03pm UTC](https://boards.straightdope.com/t/are-metal-halide-and-high-pressure-sodium-bulbs-interchangeable/711741/7 "2016-09-18T15:03:46Z")
US metal halide and HPS lamps are not interchangeable. They have substantially different arc voltages (100 or so vs 55). European HPS lamps, which use a different arc voltage, often are. A metal halide lamps is basically a mercury lamp with some nasty stuff added that increases the efficiency and color rendering and decreases the life. Older ones (probe start) use a starting electrode like mercury vapor), newer ones (pulse start) use a starter like HPS. Generally a probe start metal halide is cross compatible with mercury vapor. The current requirements are slightly higher so a metal halide lamps may not work in a mercury ballast, but the reverse is always true. Commonly ballasts were rated for both lamps, now that mercury ballasts are illegal they removed the mercury vapor rating without changing the design. For growing completely legal herbs in your basement, grow lights often use more expensive electronic ballasts that can accommodate either lamp since switching lamp types is often desirable. This is not true of the cheaper magnetic ballasts for lights on buildings. ---
**Author:** ![Jackmannii](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jackmannii/32/311_2.png) [@Jackmannii](https://boards.straightdope.com/u/Jackmannii)\ **Post date:** [September 18, 2016, 4:16pm UTC](https://boards.straightdope.com/t/are-metal-halide-and-high-pressure-sodium-bulbs-interchangeable/711741/8 "2016-09-18T16:16:53Z")
Still can’t figure why anyone would use either HPS or metal halide fixtures for outdoor illumination, given the high energy consumption and availability of (for instance) LED fixtures that provide ample light much more cheaply. ---
**Author:** ![RainPops](https://avatars.discourse-cdn.com/v4/letter/r/9dc877/32.png) [@RainPops](https://boards.straightdope.com/u/RainPops)\ **Post date:** [September 18, 2016, 4:24pm UTC](https://boards.straightdope.com/t/are-metal-halide-and-high-pressure-sodium-bulbs-interchangeable/711741/9 "2016-09-18T16:24:51Z")
hi Theyre not! Better to replace them with of course the like bulbs that you had in your mind when you typed out your post . ---
**Author:** ![Mdcastle](https://avatars.discourse-cdn.com/v4/letter/m/958977/32.png) [@Mdcastle](https://boards.straightdope.com/u/Mdcastle)\ **Post date:** [September 18, 2016, 10:20pm UTC](https://boards.straightdope.com/t/are-metal-halide-and-high-pressure-sodium-bulbs-interchangeable/711741/10 "2016-09-18T22:20:27Z")
> [@Jackmannii](#): > > Still can’t figure why anyone would use either HPS or metal halide fixtures for outdoor illumination, given the high energy consumption and availability of (for instance) LED fixtures that provide ample light much more cheaply. As a potential reasons: Maybe you got a fixture free or cheap on Craigslist Maybe you want a warm white (ceramic metal halide) or golden yellow color (high pressure sodium). I know warm white LEDs exist but in configurations other than lower lumen A19 retrofits they’re a lot less common than cool white or daylight white LEDs. LEDs just don’t look right in certain fixtures, like a clear glass globe. If you want something higher than equivalent to about 100 watt incandescent that’s omnidirectional your only option are “corn cob” LEDs that don’ t look as nice as an HID bulb. I use a 100 watt ceramic metal halide lamp bounced off the ceiling in my office. I wanted a lot of light and I couldn’t find an affordable LED fixture that produced that much. I got the fixture for $5 at Restore; it was originally a 175 watt probe start lamp that I replaced the lamp with a pulse start ceramic and the ballast with an electronic one