400 Volt 600 Watt HPS Shootout – Which is the best 400 Volt Lamp?

In our last shootout, we tested 10 different 230 volt 600 watt HPS lamps and found out which one was best. In this article we are testing four 400 volt lamps to find out which is the pick of the bunch.

400 volt HPS technology has been around in the greenhouse industry for a long time. However, it is only in the last few years that this more efficient way of driving HPS lamps has become accessible to the domestic home grower. 400 volt lamps can only be used with 400 volt ballasts. Likewise, 230 volt lamps must be only be used with 230 volt ballasts. The two types of lamp and ballasts are not interchangeable. 400 volt grow lights (the lamps, ballasts and full fixtures) are generally more expensive than 230 volt types. They claim higher light output per watt and an improved spectrum.

For this test, exactly the same setup was used as for the 230 volt lamp test. The only difference being that a 400 volt Dimlux Pro remote ballast was used rather than the 230 Adjusta-watt ballast. Everything else - the reflector, the hanging height and the cables remained exactly the same. This means that while finding which 400 volt lamp is the best, we can also test the claims of higher light output per watt and what difference there is in the output spectrums compared with 230 volt types. All of the lamps with the Dimlux ballast drew 617 watts.

The lamps on test here are:

Prices correct at time of writing.

Lets just have a quick reminder of the winner of the 230 volt roundup - the Gavita Enhanced HPS lamp. It put down a very good PPFD of 810 µmols/m2/sec directly underneath the reflector setup. Here is the Gavita enhanced light spectrum:

Right, so here is the run-down of the 400 volt lamps in reverse order:

4) The Sunmaster 400V EL Lamp

At just £34.95 (at time of writing), the Sunmaster 400V EL is the cheapest of the bunch. Like most 400V lamps, the spectrum is superior to the 230V types. The spectrum is wider at the higher end of the scale and it produces a greater proportion of its light output at 640nm and 660nm than 230V HPS lamps. Those wavelengths hit the centre of the chlorophyll photosynthesis points directly. The packaging informs us that Sunmaster class this as a Dual Spectrum Grow+ Photonic lamp. From what we can tell, the word photonic refers to the claim that there is greater spectrum consistency when it is dimmed or boosted:

In the same test setup as we used for the 230v lamps in our last test, the Sunmaster puts down 817 µmols/m2/sec. This beats the 230v Gavita enhanced lamp which was the winner of the 230v roundup. The spectrum is much wider with greater light output at the 640nm and 660nm chlorophyll points. This means that this lamp is almost certainly going to give you more productivity per watt than any 230v HPS lamp as well as likely giving you healthier plants.

3) The Sylvania Grolux 400V EL Lamp

The Sylvania Grolux 400V EL is the 400v version of their evergreen 230v lamp. However, it's not just a 400v version of the latter. The spectrum is different and contains probably the greatest proportion of red at 640nm and 660nm of all the lamps in this test. The wide spectrum will certainly help grow very healthy plants:

The Sylvania Grolux 400V EL puts down 831 µmols/m2/sec which puts it very slightly ahead of the Sunmaster.

2) The Gavita Pro Plus 400V EL Lamp

As manufacturers of some of the first 400 volt grow lights to hit the domestic market, Gavita have built up an enviable reputation for high performance equipment and we fully expected this lamp to be towards the front of the pack. And indeed it is. It has a very nice spectrum with lots of its input energy used to produce the light at 640nm and 660nm. Also notice the hump in the far-red which is great for boosting the flowering/fruiting response in plants:

The Gavita Pro Plus 400V EL puts down 856 µmols/m2/sec which is a bit of a step up from the Sunmaster and Grolux lamps. In fact, as you will see, it is only a slither less bright than the winner in this test that we considered placing this lamp in joint 1st place. This is an excellent 400v lamp and in the hands of a capable grower it will certainly produce the goods.

1) The Philips Master GreenPower 400V EL Lamp

The Gavita EL lamp and the Philips are usually regarded among growers as being the best. With the Philips Master GreenPower Plus 600W EL HPS lamp being such a coveted lamp, there are imitators out there. It's always worth checking that the stamp on the lamp itself is as above. As with all of the 400v in this test, the spectrum is nice and wide with lots of output at 640m and 660nm which means it should grow happy, healthy and productive plants.

The Philips Master GreenPower 400V EL lamp puts down 865 µmols/m2/sec which is just 9 µmols/m2/sec more than the Gavita. No matter which of these two lamps you choose you will be getting about the most PAR light for every watt of electricity you buy to run them. So, here we have 2 winners and really there is very little to choose between them. Once again we see that you really do get what you pay for with lamp performance going up as you spend a little more.

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