And how can it use "less power than a 40-watt light bulb" while it is manufacturer rated 4 amps at 12 volt = 48 watt? See here: http://koolatrononline.stores.yahoo....-fun-kool.html
BTW: You will need an additional AC/DC adapter to operate that box with mains supply.
Such thermoelectric peltier coolers make a lot of noise with their fan. And they provide only little cooling power compared to their power consumption.
Thermoelectric cooling is inefficient, the cooling power is about 2/3 of the electrical power consumption, so if such a device consumes 48 W, it will provide roughly about 48*2/3= 32 W cooling power.
If you intend to create a heat exchanging device from this box and your growing chamber, you could pump water to and fro, need an aquarium pump with about 5 W and this already is a new heating device in your circulation. Substract 32 W - 5 W and there will be a total of 27 W of cooling power that arrives in your growing chamber.
How good is the insulation of your growing chamber? How low can the temperature go with just 27 W of cooling power?
On the other side: Compressor coolers can easily provide 2/3 more(!) cooling power than they consume as electrical power. So a 48 W compressor cooler provides roundabout 48*1,666 = 80 W of cooling power. Reduce by 5 W for the pump are 75 W remaining.
So from 48 W of electrical power input you can have either 27 W of cooling power with a peltier cooler or 75 W of cooling power with a compressor cooler. Pretty much different, isn't it? Efficiency is much higher with compressor coolers!
Unfortunately, compressor coolers are more expensive and (in most cases) louder than thermoelectric coolers. And the cooling power range starts with compressor coolers where it ends for thermoelectric coolers.
But long speech, short point: I doubt that a thermoelectric cooling box provides enough cooling power to lower the temperature in a growing box by a significant amount.