Output and efficacy: 15 HPS lamps in the test

Lux Light InternationalLighting

Light Test

Plant lighting with HPS lamps is a standard in professional horticulture: Not only the low initial costs per square meter of area make HPS lighting a cost-effective lighting solution for plant cultivation. The industry can also rely on more than 20 years of experience with HPS technology.

Currently, a variety of different HPS lamps are available in the market from diverse brands and manufacturers in different price segments. In addition to the established brands such as Sylvania, OSRAM and others, there are more and more brands and products in the low-price segment, especially in the last few years.

We asked ourselves the following questions:

  • How do the different lamps perform regarding performance and efficacy?
  • Are there differences in the performance of brand products and private label lamps?
  • Do the test results correspond to the specifications of the manufacturers on the data sheets and product packaging?
  • How competitive is one of our top sellers among HPS lamps, the Sylvania Grolux SHP-TS 600W 230V compared to other products in the market?

For explanation: HPS (lamp) stands for “High Pressure Sodium (lamp)”

The Test Scope:

We tested and compared 600W 230V HPS lamps with E40 socket from 15 brands of different manufacturers with different manufacturing locations and price ranges. The retail price of the cheapest lamp was 25€, that of the most expensive lamp was 59€.

The lamps were ordered from different retailers, the selection of the lamps did not follow a specific rule, rather it should represent a sample selection of today’s common HPS lamps.

This also guarantees that no manufacturer provides a specially prepared version of its lamp for testing.

The Test Process:

To ensure a consistent basis for comparison, the “burn-in” of new HPS lamps is important for a consistent output and to avoid large variations in output. It is performed by some manufacturers themselves, while other manufacturers leave this to the customer.

For the test, the lamps were burned in for 100 hours on an IES (Illuminating Engineering Society) compliant ballast. This device ensures that the lamps are not burned in too quickly or too slowly. It also ensures that the burn-in phase is not dependent on a particular ballast manufacturer.

The Test in the Ulbricht Sphere:

For the test, the lamps were connected to the respective ballast and operated centrally in an Ulbricht sphere to ensure optimal comparability of the measurement results. The PPF value was measured in µmol/s, i.e. the photon flux or the amount of light usable by plants.

An Ulbricht sphere (integrating sphere) allows accurate measurement of the total PPF output of a light source in µmol/s due to its optimal reflectance properties and is used as standard in scientific light measurements.

In contrast to the absolute PPF output, the relative PPFD value depends on many additional factors such as the reflector, reflecting walls, the floor, the ceiling or the distance from the lamp to the measuring head, so only the PPF value was measured. The evaluation of the data was automated, all measurement data were collected and stored in a database.

The ballasts applied – magnetic vs. electronic

A ballast is needed to ignite HPS lamps and to supply them with power during operation. Ballasts come in two types: magnetic ballasts (MB) and electronic ballasts (EB). Magnetic ballasts are usually inexpensive and very durable, but have somewhat higher inherent power consumption and are only rated for a specific wattage at a time.

Electronic ballasts have a power factor of up to 0.98 and are also dimmable, so they are also suitable for different wattages.

In the test, two ballasts were chosen as representatives of their type.


Magnetic Ballast:Electronic Ballast:
EuroGearPro 600W BallastElectronic Ballast Symbol Picture
Eurogear Pro 600WDimmable EB 400-600W (Symbol image)

The Results:

PPF measurement on the magnetic ballast

On the Eurogear Pro 600W magnetic ballast, almost all of the 15 tested lamps showed higher PPF values than on the electronic ballast. The Sylvania SHP-TS Grolux 600W achieved the highest PPF value with 1,132 µmol/s and was still 52 µmol/s stronger than on the electronic ballast.

Efficacy at the magnetic ballast

When measuring efficacy, almost all the lamps tested achieved the same or slightly higher efficacies on the magnetic ballast than on the electronic ballast. Here, the Sylvania Grolux SHP-TS 600W achieved with 1.81 µmol/s/W the best value of all 15 tested lamps.

PPF measurement on the electronic ballast

At the electronic ballast, the various lamps performed with PPF values of 925 to 1080 µmol/s. Only four of the 15 lamps tested achieved a PPF value higher than 1000 µmol/s. The Sylvania SHP-TS Grolux 600W had the highest output with 1080 µmol/s.

Efficacy at the electronic ballast

Regarding the efficacy, the different lamps showed partly very varying values from 1.55 to 1.78 µmol/s/W. The Sylvania SHP-TS Grolux 600W achieved the second best efficiency here with 1.77 µmol/s/W.

Lamp No. 5 achieved the top value of 1.78 µmol/s/W here. It was specially optimized by the manufacturer for operation on electronic ballasts and was the most expensive of the lamps tested.

The Results:

Maximum output – the PPF value

The relatively large fluctuations in output between the various 600W lamps of the tested brands were remarkable. Both in the test on the magnetic VSG with 24% (Δ 224 µmol/s, min. 908, max. 1,132), and on the electronic ballast with 16% (Δ 155 µmol/s, min. 928, max. 1080).

According to their data sheets, none of the 15 tested lamps had an output of less than 1,050 µmol/s – in fact, only five manufacturers achieved the specified output when tested on the magnetic ballast, and only two on the electronic ballast. Lamp No. 9 with measured 928 µmol/s was even 12% below the PPF output in the data sheet.

The Sylvania Grolux SHP-TS 600W had the highest output on both ballasts. At the magnetic ballast, it achieved a very good efficiency of 1.81 µmol/s/W, which can even keep up with some LED luminaires. On the electronic ballast, it also performed very well with 1.77 µmol/s/W.


When measuring the lamp current (the power consumption of the lamp), it became clear that the electronic ballast operates more power-efficiently. In the midfield of the candidates, the total output is thereby marginally reduced, but the efficacy is increased.

The magnetic ballast supplies the maximum energy that the lamp’s burner can utilize. This is not necessarily power-saving but some lamps benefit significantly here.

Three (EB) and four (MB) lamps had efficiencies below 1.6 µmol/s/W, while four lamps each achieved efficiencies above 1.7 µmol/s/W. The Sylvania Grolux SHT-PS 600W 230V achieved very good values on both ballasts with 1.77 and 1.81 µmol/s/W respectively.

Recommendation – Best practice:

In terms of both output and efficacy, the Sylvania Grolux SHP-TS 600W 230V performed best in a direct comparison with all other lamps. In combination with the Eurogear Pro 600W magnetic ballast, it represents a lighting solution with very good performance, high efficacy and long life.


Unfortunately, we cannot give the names of the tested lamps. Like any technology, the HPS technology is subject to certain fluctuations in production, therefore the measured values do not represent a generally valid measurement, but correspond to the tested lamps at the time of testing.