600w 230v HPS Grow Lamp Shootout – We find the Best 600w HPS Bulb!

600w 230v HPS Grow Lamp Shootout - We find the Best 600w HPS Bulb!

The Future is Bright! (as long as you choose the right grow lamp)

There is a bewildering number of different brands and models of 600 watt grow lamp on the market. If you are putting together the equipment for your first grow, or just looking to replace your ageing grow lamp, how can you know you are making the best choice?

Prices for 600 watt grow lamps vary a great deal. At the lower end, one can be had for as little as £14.95, while higher-end lamps can cost a lot more up to around £43.95. But do the more expensive lamps justify their premium price?

We rounded up a sample of all the single-ended 600 watt lamps that we stock (and some we have previously stocked alongside samples we've been sent), and then performed a comparative test on them to find out which are the good ones and hopefully find which are the winners in the 600 watt HPS category. We tested the following 600 watt HPS grow lamps:

Most (if not all) 600 watt grow lamps look very similar. Usually, the main visual difference in the lamps is the writing on them which identifies the manufacturer and sometimes the part number. The glass jackets all look very similar, as do the elements and their internal wire support frames.

The Testing

The human eye is not a good enough tool for assessing grow lamps. HPS lamps produce an intense orange-red light. All of the different models are so bright that it is virtually impossible for the human eye to discern which ones are the brightest. The differences in the colour spectrum that they produce, again are too slight to be judged by human sight alone. For taking a look at the spectrums, we used a Sekonic Spectromaster C-7000 Spectrometer.

If you look closely at the spectrum graphs for the lamps you will probably notice that they have a lot of similarities. Their light output is very heavily biased toward the orange-red part of the spectrum. Relatively little light of other colours is emitted by any of them. Even the so-called "Dual Spectrum" lamps produce barely any blue.

In order to make fair comparisons, we chose a digital ballast (an Adjusta-Watt), and a fairly commonly used Euro (or barn-type) reflector; which was suspended at a fixed height from a rigid frame. The setup needed to be consistent - in other words, it needed to be an identical testing environment for all the lamps. All unnecessary movement of the equipment was pretty much eradicated, and a single point was chosen beneath the reflector to measure the PPFD.

In an ideal world, we would measure the total PPF output of each lamp. Unfortunately, to do this we would need something called an integrating sphere which is an incredibly expensive piece of equipment and is rarely found outside of a scientific light testing laboratory. However, in a fixed system, the PPFD at a fixed point is relative and proportional to the total PPF output of the lamp.

Each lamp was given 3 hours to warm up, settle down, stabilise, and burn in a little. Ideally, we would have allowed a longer burn-in time. The PPFD was then measured at a fixed spot with our Li-Cor PAR meter, and a snapshot of the spectrum was taken with our Sekonic C-7000 spectrometer. Lamp swap-outs were performed almost surgically with the utmost care being taken to not allow any equipment to move. PPFD was measured in µmols/m2/sec.

We also used a plug-in power meter to measure the amount of power being drawn from the mains outlet. We thought that different lamps might draw different amounts of power, however we found that in this setup (which includes a digital ballast), all the lamps drew exactly the same amount of power (609W). This might be due to the Adjusta-watt digital ballast control circuitry accurately delivering the right number of watts into each of the lamps. It may be the case that if we had used a standard magnetic core & coil type of ballast, the electricity draw would have been different for the different lamps. We realised that, actually, having the same power draw across all of the lamps from the wall was not a bad thing. It meant that any rogue lamp which drew more power and thus achieved high PAR reading was not a possibility using this ballast. It provided a much more level playing field for all the lamps.

So, the expectation was that the better (more expensive) lamps would output more PAR light and possibly a better spectrum. For the test, we've included the spectrum graphs for each of the lamps in this report. At a glance, the spectrum graphs look pretty much the same, but there are small and important differences.

It's also worthwhile remembering that HPS lamps concentrate their output in the orange-red part of the light spectrum; light in this region is the most efficient for promoting flower and fruit production from a plant.

Many growers will know that there are 2 types of chlorophyll in a plant - chlorophyll a and chlorophyll b. Each has a peak in the blue part of the spectrum and a peak in the orange-red part of the spectrum. Although chlorophyll is not the only compound in plants that collects and converts light to energy, it is the one that is most commonly known and understood.

There are some key wavelengths in the red that we can use to get an idea of how productive a spectrum is:

  • 640nm - Peak red absorption wavelength of chlorophyll B
  • 660nm - Peak red absorption wavelength of chlorophyll A - v.important!
  • 680nm - Peak action wavelength for photosystem II (P680)
  • 700nm - Peak action wavelength for photosystem I (P700)
  • 710-780nm - Far red light for plants

It is good for a grow light to emit light across the whole 640-700nm band. This why the width of the red band at the end is important.

Far red light can stimulate a bit of extra terpenoid production, but it can also cause stem elongation (stretching) which is usually inconvenient for the grower and counter-productive in terms of yield. Far red light can be utilised to good effect, but mainly if it can be used on its own for about 15 minutes straight after the main grow light has gone out. Obviously, this is not possible with an HPS light where it is either on or off.

The Photosystems I and II are less well known. They are light reaction centres which work at the wavelengths of 700nm and 680nm respectively, which is why they are sometimes referred to as P700 and P680. The photosystems are groups of pigments which carry out a complex series of reactions called the Calvin cycle. It's interesting that when P700 and light with a wavelength of around 670nm is used, the amount of photosynthesis they produce is greater than the sum of the amounts they would produce individually. This is called the Emerson effect.

As we said before, chlorophyll does not tell us the whole story. There are several compounds within plant tissue that can collect light. The energy collected by these other compounds from light is then passed on to the chlorophyll which then performs the energy-to-sugar conversion process. The relative amount of photosynthesis produced at all the PAR wavelengths is depicted by the McCree curve (which we have overlaid onto our spectrum graphs). However, it would stand to reason that as well as stimulating the other light collecting compounds within the plant, it would still be quite important to drive the chlorophyll directly with light at 640nm and especially at 660nm.

The McCree curve gives an idea of how photosynthesis is produced by different parts of the light spectrum. It is interesting to note that although a photon of blue light contains more energy than a photon of red light, the photon of red light will actually drive a similar amount of photosynthesis as one of blue light. However, because it takes more energy to produce the blue photon, you will get more photosynthesis by using your electricity to produce red photons. The McCree curve illustrates this by showing (in relative terms) how much photosynthesis is driven across the PAR spectrum (400nm-700nm). For this reason, we have overlaid the McCree curve onto our spectrum graphs. For plant health and efficiency, we were looking at the width of the main part of the orange-red spectrum (mostly around 600nm) and how much was relatively produced slightly higher up at those key wavelengths of 640nm and 660nm.

The Results:

11) The FireFly HPS Lamp

The FireFly is a budget-end HPS lamp. It can be found around the internet for the remarkably low price of about £12.95. As such, it is one of the cheapest of the bunch. In this test the FireFly was putting down 667 µmols/m2/sec. The spectrum:

Relative intensity (400-700nm) at the key points:

  • 640nm Peak Chlorophyll B - 3.7%
  • 660nm Peak Chlorophyll A - 2.7%
  • 680nm Photosystem II - 2%
  • 700nm Photosystem I - 1.2%
  • 730nm Far Red - 1.3%

Although the FireFly produces a similar orange-red light as all HPS lamps, the spectrum shows us that its main output band in that region is actually a little bit narrow and it produces comparatively less light from 630nm upwards. Overall, this lamp does not offer the same performance as the more expensive lamps in this test. In fact, it was so disappointing that One Stop Grow Shop decided to discontinue stocking it. Tested - September 2018

10) The LUMii Sunblaster HPS Lamp

One Stop Grow Shop don't stock the LUMii Sunblaster, but it is available on the internet for about £15.00. We clocked the Sunblaster's output at 724 µmols/m2/sec which, while better than the FireFly, it still does not approach the light output of the better grow lamps in this test. The spectrum:

Relative intensity (400-700nm) at the key points:

  • 640nm Peak Chlorophyll B - 8.9%
  • 660nm Peak Chlorophyll A - 6.1%
  • 680nm Photosystem II - 4.4%
  • 700nm Photosystem I - 3%
  • 730nm Far Red - 2.3%

The main orange-red band is slightly broader than the FireFly and has more output from 640nm upwards. However, like the Firefly, the results were disappointing, and One Stop Grow Shop decided to discontinue stocking it. Tested - September 2018

9) The LUMii Black HPS Lamp

The LUMii Black Dual Spec HPS Lamp would seem to be the replacement lamp for the LUMii Sunblaster lamp above. It can be found for about £14.95 at certain outlets. The LUMii Black kicks out 745 µmols/m2/sec which is definitely a worthwhile improvement over the LUMii Sunblaster. The spectrum:

Relative intensity (400-700nm) at the key points:

  • 640nm Peak Chlorophyll B - 11.3%
  • 660nm Peak Chlorophyll A - 7.8%
  • 680nm Photosystem II - 5.7%
  • 700nm Photosystem I - 3.8%
  • 730nm Far Red - 2.8%

The spectrum looks like it has been very slightly improved too. The main band is very slightly wider and the light output above 640nm is very slightly higher too. Tested September 2018

8) The Ultra Vivid HPS Lamp

The Ultra Vivid HPS lamp is available from One Stop Grow Shop for £14.95. This little fella kicks out 747 µmols/m2/sec which is in the same ballpark as the LUMii Black. The spectrum:

Relative intensity (400-700nm) at the key points:

  • 640nm Peak Chlorophyll B - 11.7%
  • 660nm Peak Chlorophyll A - 8%
  • 680nm Photosystem II - 5.9%
  • 700nm Photosystem I - 4%
  • 730nm Far Red - 3%

The spectrum coming out of the Ultra Vivid is the best so far with the orange-red band being the widest. The output above 640nm is slightly higher than the FireFly or the LUMii lamps. This will please your plants and will likely lead to better plant health and yields too. Tested September 2018

7) The Street Light Lamp

The Street Light 600w HPS is a relatively new kid on the block. It sits at the budget end of the market, retailing for just £14.95. We were very keen to see how this lamp fared compared to its rivals at around this price-point. We were stunned by the output of this lamp which turned out to be 770 µmols/m2/sec. At this level it absolutely trounces other budget HPS lamps and it is really beginning to compete with the big boys. The Spectrum:

Relative intensity (400-700nm) at the key points:

  • 640nm Peak Chlorophyll B - 11.3%
  • 660nm Peak Chlorophyll A - 7.7%
  • 680nm Photosystem II - 5.6%
  • 700nm Photosystem I - 3.9%
  • 730nm Far Red - 2.8%

The Street Light not only offers a very impressive PAR output but an excellent spectrum too. The orange-red band is nice and wide and the output above 640nm is great. This Street Light will definitely deliver the biggest and healthiest crops of all the lamps tested so far. This lamp gives you far more than you would expect at this price-point. This was very highly recommended but sadly, shortly after this test it became no longer available. Tested September 2018.

6) The Sol Digital Lamp

The Sol Digital lamp retails for £19.95 at One Stop Grow Shop. It provides a slightly greater output than the Street Lamp giving out 780 µmols/m2/sec at our test point. The spectrum:

Relative intensity (400-700nm) at the key points:

  • 640nm Peak Chlorophyll B - 8.3%
  • 660nm Peak Chlorophyll A - 5.7%
  • 680nm Photosystem II - 4.2%
  • 700nm Photosystem I - 2.8%
  • 730nm Far Red - 2.1%

The width of the main orange-red band is good and there is a nice amount of output above the 640nm region. We know that our customers have great results with this lamp which would back up the findings from the testing. At 780 µmols/m2/sec PPFD at our test point, it can drive the most photosynthesis of all the lamps so far. Tested - September 2018

5) The Omega HPS Lamp

The Omega HPS lamp at £19.95 is generally thought of as being a good budget lamp. It is frequently purchased as part of a budget grow light kit. However, One Stop Grow Shop stocks this lamp for purchase separately.  In our original test the Omega was putting down 755 µmols/m2/sec. However, they have recently updated the lamp and out of 3 tested, the average was 790 µmols/m2/sec. The spectrum:

Relative intensity (400-700nm) at the key points:

  • 640nm Peak Chlorophyll B - 5.33%
  • 660nm Peak Chlorophyll A - 3.6%
  • 680nm Photosystem II - 2.7%
  • 700nm Photosystem I - 1.9%
  • 730nm Far Red - 1.4%

The spectrum shows that the approximate intensity (relative to the peak intensity) above 640nm is approaching that achieved by the Ultra Vivid. However, the increase in PAR light output that you get with the Omega means higher yields could be possible. Sample of 3 tested - October 2019

4) The Sunmaster HPS Deluxe Lamp

The Sunmaster Deluxe has been around for many years and it has built its reputation on the claim that it outputs 95,000 lumens (which is considered very high for a 600w HPS lamp). It retails for £24.95. Lumens does not directly translate into PAR. In other words, a very high lumen output does not necessarily mean that it will drive the highest levels of photosynthesis. It simply means that it appears particularly bright to our human eyes. Fortunately for Sunmaster, the PAR light output is very good too - it was measured to be 791 µmols/m2/sec which just barely beats the Sol Digital. The spectrum:

Relative intensity (400-700nm) at the key points:

  • 640nm Peak Chlorophyll B - 6.8%
  • 660nm Peak Chlorophyll A - 4.7%
  • 680nm Photosystem II - 3.4%
  • 700nm Photosystem I - 2.3%
  • 730nm Far Red - 1.8%

The spectrum would have been better if the orange-red spectrum was a touch wider and there was slightly more light output above the 640nm region. Still, the Sunmaster Deluxe is still a highly popular lamp and with its great PAR output has the potential to produce very pleasing sized crops. Tested - September 2018

3) The Sylvania Grolux Lamp

In number 3 position, the Sylvania Grolux HPS lamp is another lamp that has proved its popularity over time. It claims to produce 90,000 lumens (5000 less than the Sunmaster). It would make sense, given the lower lumen output, that it is slightly cheaper at £22.95. However, as we know, lumens do not necessarily correspond to PAR output and indeed this is the case here. The Sylvania Grolux produced 802 µmols/m2/sec - the best so far, and a bit higher than the Sunmaster. The spectrum:

Relative intensity (400-700nm) at the key points:

  • 640nm Peak Chlorophyll B - 12.7%
  • 660nm Peak Chlorophyll A - 8.7%
  • 680nm Photosystem II - 6.4%
  • 700nm Photosystem I - 4.3%
  • 730nm Far Red - 3.2%

Not only is the PAR reading very high but the width of the orange-red spectrum is the best so far, as is the amount of output in the region above 640nm. This lamp should really deliver the goods in terms of yields and plant health. At this price, how could you go wrong?? - Great value-for-money! Tested - September 2018.

2) The Gavita Enhanced HPS Lamp

And so we finally come to our winner. The Gavita Enhanced HPS Lamp was introduced a few years back with a design meant to make the most of digital ballasts. At £29.95 it is one of the most expensive of the bunch, but the performance reflects this as it puts down 810 µmols/m2/sec. This puts it in first place. The spectrum is impressive too:

Relative intensity (400-700nm) at the key points:

  • 640nm Peak Chlorophyll B - 15.8%
  • 660nm Peak Chlorophyll A - 10.9%
  • 680nm Photosystem II - 8%
  • 700nm Photosystem I - 5.2%
  • 730nm Far Red - 3.9%

The spectrum has a great width to its orange-red band and output above 640nm is excellent too. It also puts a little icing on the cake with a pretty high output in the far-red. During flowering far-red can improve the flowering response in many plants. Part of the design is that it has a much improved element support frame inside. This makes it less likely to distort due to the high frequencies produced by digital ballasts. Great PAR light output, great spectrum, and robust design go together to make this lamp the top dawg. Tested September 2018.

1) Philips Master GreenPower Son-T PIA CG-T Lamp

Philips have an awesome reputation with their Philips GreenPower range of HPS lamps. At £43.95 it is quite a bit more expensive than the rest, but this is reflected in the performance - 818 µmols/m2/sec - easily the best of the bunch.

Relative intensity (400-700nm) at the key points:

  • 640nm Peak Chlorophyll B - 16.3%
  • 660nm Peak Chlorophyll A - 11.2%
  • 680nm Photosystem II - 8.3%
  • 700nm Photosystem I - 5.5%
  • 730nm Far Red - 3.7%

Just take a look at the width of the highly productive red end of the spectrum. It emits the largest amount of light in the 620-700nm part of the spectrum. Although this lamp costs a bit more, the user is very likely to make the extra cost back in terms of increased yield. Philips remain the king of HPS! Tested February 2019.


The scope of this test meant that only one sample of each lamp was tested. It is entirely possible that we had some particularly good examples of some lamps and some lower quality examples of others. It would have been better if several examples of each had been tested and an average taken. For this reason, the results should only be used as an indication rather than for anything absolutely definitive.

This roundup of HPS lamps shows that spending that little bit extra on your grow lamp really does make a difference to the quality. A small additional spend at the start of your grow can reap huge dividends in the size and quality of your crop.

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