The numbers are heavily influenced by cost of electricity and time of use. Payback ranges from 1-5 years with an average user seeing payback in about 3.

Average 600W HPS lamps are 1.0-1.3 µmoles/watt. A complete fixture consumes 660 watts with ballast losses. They generally lose about 20% of their light due to reflectors (omni-directional lamp in a directional application).

This means that our 2.0 µmoles/watt fixture at 230 watt consumption can replace a 660 watt HPS fixture, provide the same amount of light, and have a nice payback.

Here's what I didn't get from your website: there are typically two wavelengths you're interested in for growing plants, depending on the phenological stage: a red and a blue (I can't remember the exact numbers, but the band is quite narrow). How can it be that your lamps have higher efficiency despite providing a complete spectrum? I don't know anything about light physics, hence my question; intuitively, I'd say you could have higher 'yield' by focusing all energy you put in to one wavelength (or at least, a narrow band).

It turns out that plants use more than just red/blue for photosynthesis. They do indeed absorb narrow bands of red/blue more strongly than other colors like green (this is why plants are green) but only absorb about 10% more efficiently.

The green light not absorbed is reflected. This gives the opportunity for green photons to reflect their way down to the bottom leaves for a more distributed growth.

We have built a number of lights with "focused" spectrum but haven't seen a benefit. In many plants, like "red" lettuces the leaves only turn red with a full spectrum (I have no idea why, a botanist might know the answer...)

We do see a benefit to skew the spectrum for many flowering/fruiting plants in later growth cycles and have a plan to come out with a "fruiting spectrum" in the future. This will part of our August Indiegogo campaign.

Interesting. I do admit that much of what I know comes from books written for growing marijuana, since until a few years ago those were almost the only (large scale) applications of indoor growing, and that most of that knowledge isn't very scientific (for example until a few years ago the mainstream technique to force bloom on mj plants was to vary the light cycle only). Research is frantic in the field, a fascinating development.

One last question if you don't mind: do you see a market for this in small scale operations, or do market pressures force your customers to grow always bigger like in the rest of agriculture? It seems that the only (sustainable) way to make a profit on growing food (plants and animals) is by scaling up.

(OK I lied, I have another question actually: with the pressure on lighting system vendors in Europe to screen their customers for illegal operations, and increasing pressure to hold vendors accountable for such use, are you experiencing that American vendors actually have a market advantage on this? Do you export to Europe? (meta: who would have thought just 10 years ago that in 2015 the US would become the world's leader on high tech marijuana production!) also sorry for focusing on mj, your industry suffers from its association with it, I know - it's just that that market was the only non-academic source of knowledge on it for so long)

It will be interesting to see how the market scales. There are certainly advantages to large commercial greenhouses etc... but there is a quickly growing trend for small local producers that grow a few hundred or couple thousands plants at a time. They might service a grocery or a few restaurants. There is also a trend for people to grow at home, grove labs was already mentioned in this thread as an example. My guess, ultra-efficient, nearly fully automated indoor production facilities will be a major player. Labor and energy are the two biggest costs to production and there are emerging technologies to address both of these.

Regarding Europe, it hasn't been a primary focus for us but we have exported a few orders to the UK, Germany and Netherlands. I hadn't heard of pressure on vendors to screen their customers. I'll have to look into this.

Our orders so far have split about 50:50 between veggies and marijuana. The marijuana side of the business does certainly seem to overshadow the veggie side as far as general public interest goes!

Thanks for your answers, and best of luck with your business.