The cheapest option in my opinion is building your own, if you are talking walk in cooler size. The first one I constructed for around a thousand dollars, give or take, for the structure itself. Add to that the cooling and humidifying mechanisms. We used an lg air conditioner interfaced with a coolbot unit (look it up), which worked sensationally. This all will bypass the need for a charged condenser system which may require a professional to install. The former situation is almost turnkey. For humidity there are a lot of options, but one we have used is a hardwired humidistat which can regulate a vaporizor, fogger, etc. This is also cheap. Setups like this allow for a lot of tweaking, the replacement of parts that do not work or do not last and so on. If you buy a prefab system and you do not like it, there is little you can do to alter it. Our first cooler, an 8 x 12 for all the above (my labor for construction and wiring) was around 1500.00. (This would be a few hundred more normally, as I had some used parts).
For all those out there with small amounts, and own a freezer, there are units (think 50-100 bucks) that will turn it into a fridge, allowing dual purposing. I find this handy as the freezer is empty before a chicken slaughter, etc, and can be used for small amounts of early apples, etc, fitting 5 or 6 bushels.
And for anyone planning for a big operation, please, please think subterranean. By starting with a true cellar you not only begin with a lower temp, you have a huge buffering capacity. That is, it will moderate very slowly and avoid wasting energy when temps and humidity outside fluctuate wildly as they often do.
Finally, with anything in a normally unheated space, you will likely need, ironically, heating arrangements. Here, as early as September we can have temperatures that would freeze the stored fruit. Here, too, the cellar sytem would be handy. There are plenty of heating situations apparent to us all, but if the space is properly insulated, a cheap 1500 watt space heater with timer or thermostat is easy to deal with and typically hit you for only 25 cents an hour at full capacity.
Walden Heights Nursery & OrchardZone 3 in Vermont
Edited 2 time(s). Last edit at 12/16/2016 11:19AM by Todd Parlo.