The Gavita Pro 750e Grow Light – Awesome Efficiency and Flexibility!

How to Increase Yields and Efficiency!

Not so long ago, Gavita introduced a new wattage HPS grow light onto the market - the Gavita Pro 750e. For many, many years, there was only a small handful of sizes (wattages)  of HPS grow light to choose from. There was the small 250W, the medium 400W, the larger 600W, and the grand daddy of them all - the 1000W for the really serious grower. So why did Gavita decide to produce a 750W HPS light? What is it designed for, and for what sort of grower is it intended? Let's delve into the matter and find out....

For a long time, the 600 watt HPS has been the most popular size of grow light (particularly in the UK). There are good reasons why the 600 watt HPS became the most commonly used size. To start with, the 600W HPS grow light held the reputation of being the most efficient of all the sizes. If you take a particular manufacturer's range of HPS lamps you will almost always find that the 600 watt version kicks out slightly more PAR light per watt of electricity than any of the other wattages in that same line-up.  Along with the fact that a 600W HPS grow light is powerful enough for a very worthwhile size grow, yet produces considerably less heat than a 1000 watt HPS, it is not difficult to understand the popularity of this size of grow light.

Matching a Grow Light to the Grow Area

For any given wattage of grow light there is a sweet-spot in terms of the size of area that it will cover and still be able to produce worthwhile growth. If the area you are trying to cover is too large then those parts of the plants around the edges of the grow-space will produce weak (and probably unworthwhile) levels of growth. If the area is too small then the light levels will be so high that plants cannot make the most of it all, reducing garden efficiency in terms of yield per watt. That also comes along with attendant heat problems from using too high a power of lamp in too small a space. While the reflector in a system makes a difference to the shape of the footprint, ultimately it is the wattage (and efficiency) of the lamp that really dictates the size of the usable grow area.

Over the years, it became accepted wisdom that an area of 1.2 metres square pairs up very nicely with a 600 watt HPS grow light. Hence, for many growers, the partnership of a 600 watt grow light for efficiency and a 1.2 metre square tent has become probably the most popular "go-to" setup.

A Leap in Efficiency Arrives!

While the domestic market was limited to the standard 230 volt HPS systems for a long time, 400 volt HPS systems were being used as supplementary lighting in the commercial horticultural industry. The 400 volt system for driving HPS lamps is more efficient than the standard 230 volt system, but the technology simply wasn't made available to hobby growers until Gavita developed their Pro Series HPS fixtures a few years ago. At last, hobby growers had access to the 400 volt systems which produce between 10% and 25% more light than the standard 230 volt systems, raising garden efficiency without any extra heat to deal with.

Gavita initially launched the range with a 600 watt fixture and followed that up with a double-ended 1000 watt version. After the launch, for those growers wanting the best 600 watt grow light that they could get their hands on to use in their 1.2m square tent, the Gavita Pro 600 became the natural choice.

Light Footprint for the Gavita Pro 600W Grow Light in a 1.2m Square Area

The Go-To Top-Flight Setup

When we began stocking the Gavita Pro 600W grow light, it was our top recommendation (for growers using a 1.2 metre square grow tent). Of course, the next step up from a 600 watt Gavita Pro grow light was the mighty DE 1000 watt version - which produces a big step up in light production, but with an accompanying step up in heat production. The acknowledged sweet-spot for a 1000 watt grow light is a 1.5m square area. 1000 watters are just too much, or so we thought, to be used in a 1.2m square space....

Everyone Likes to Get A Bit Extra!

Although a Gavita Pro 600 watt HPS in a 1.2 metre square tent is one of the most efficient combinations you can get (in terms of yield per watt), it is still possible to produce bigger crops from that size space by using a higher wattage grow light. As a result, Gavita were finding that some growers with a 1.2m square tent were combining it with a Gavita Pro 1000 watt light instead of the more commonly used 600 watt version.

While there is big potential for getting larger yields by using a 1000W HPS in place of a 600W light, the problem with using such a high power light in a 1.2m square size space is not only one of heat but also of efficiency. In the hands of a good grower, using a larger grow light will typically cause total yield to go up. However, unless environmental factors such as temperature, humidity (and therefore Vapour Pressure Deficit, or VPD) are dialled-in almost perfectly, plants simply cannot make full use of all that extra light. The end result is that although total final yield will go up, the actual final weight of product per watt of electricity that is achieved will almost certainly go down. In other words, garden efficiency is very likely to drop.

Increased Light Means Increased Heat

Of course, to help combat the problem of the extra heat, a grower's extraction system can be upgraded. Also, the Gavita Pro 1000 watt grow light can be dimmed or boosted to run at any one of 6 settings - 600w, 660w, 750w, 825w, 1000w, 1150w. The ability to run the grow lamp at one of the lower wattages means that during the warmer months the issue of heat can also be managed by dimming the light (and thus reduce the amount of heat produced by it). All of this meant that growers would be gaining the opportunity to crank up the wattage (and therefore the light output) whenever temperatures allowed, thus increasing final yield, at the expense of some efficiency.

After talking to growers running a Pro 1000 in 1.2m x 1.2m tent, Gavita found that (given favourable environmental conditions) most gardeners were able to successfully grow by running it at the 825w setting at most times of the year.

Getting the Most from Every Watt

The issue of garden efficiency is a big one. High Intensity Discharge (HID lamps) are designed to reach their optimum temperature when they are running at their nominal wattage. i.e a 600 watt HPS grow light will be at its most efficient when run at 600w rather than when it is either dimmed or boosted. By running a HPS lamp at a different wattage to its nominal rating, its operating temperature will be different to the optimum design temperature. As a consequence, the output spectrum changes slightly and also the PAR per watt efficiency is reduced. An HPS lamp produces its highest μmols/watt output only when it is driven at its designed wattage. i.e. at 1000 watts. A 1000 watt lamp run at 600 watts will not produce 60% of the PAR that it does at 1000 watts. It will produce less. To compound the problem, the light spectrum alters too, with slightly less of the light being produced at the peak photosynthetic wavelengths.

The hotter or cooler a lamp is from its designed working temperature, the more efficiency that is lost. This is the reason why Gavita have always said that their grow lights should not be cooled by a fan blowing directly at the lamp.

Gavita Introduce the First 750 Watt HPS - Bringing the Efficiency Back to Upgraded Lighting

Gavita worked on the problem of reduced efficiency for their customers. The end result is that Gavita developed and introduced their Gavita Pro 6/750e. This grow light bridges the gap between the Pro 600 and the Pro 1000.

Like the Pro 1000, the Pro 750e utilises a double-ended lamp and can be set to run at different wattages - 400w, 500w, 600w, 750w or 825w. However, inside the Pro 750e, Gavita have developed some clever technology which minimises the detrimental effect of running a lamp dimmed or boosted. This means that a Gavita Pro 750e boosted to 825 watts produces more PAR, a better spectrum, and less heat than a Pro 1000 dimmed down to 825 watts.

The superb efficiency of the 750e means that potential yields are fairly close to those which can be achieved with a 1000w Gavita Pro grow light being run at 1000 watts. In fact, as it turns out, the 750e is the most efficient grow light in the Gavita Pro range.

Since the inception of the Pro 750 by Gavita, we have had a large number of customers try one out in a 1.2m x 1.2m grow tent and have been absolutely delighted with the results.

Of course the Gavita Pro 750 doesn't have to be used in a 1.2m x 1.2m tent. In fact, greater yields will be had from a larger tent such as a 1.5m x 1.5m or the excellent 1.8m x 1.1m BudBox GT1 Grow Tent (if you have the space). However, if you have a 1.2m x 1.2m tent and you are looking for an upgrade from your 600w grow light then the Gavita 750e is the perfect answer for maintaining as much garden efficiency as possible. Just make sure that your extraction system is going to be up to the job of removing that bit of extra heat that it produces.

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