Product review (4 stars): Unique, Reliable, and Flexible
Buying a Sundanzer involves some choices. First is the size. If you have the space, get the largest unit. The reason is that the compressor is the same for all of them, and the only thing that changes is how often the compressor cycles. So the largest one will draw the same number of watts; it will simply do so a bit more often (using more watt-hours overall). After deciding on the size, you'll have another difficult choice to make: fridge or freezer. In fact there's absolutely no difference between the two except for the thermostat used. You could, as I did, get both thermostats. Then if you later decide you'd rather have a fridge instead of a freezer (or vice-versa), you can swap them in a fairly easy operation.

My unit is currently set up as a fridge. I keep it packed at the coolest setting in a hot garage. The temperature inside stays just above freezing. To accomplish this, the unit consumes approximately 300 watt-hours per day (drawing around 45 watts while the compressor's active). That means a 250 amp-hour 12-volt deep cycle battery will keep this arrangement going for 10 days (assuming you don't mind draining and possibly damaging the battery; normally you don't want to go below 50% of the battery's capacity).

The scenario I've described is fairly demanding; during an extended power outage you'd probably want to adjust the thermostat to something more reasonable than just above freezing. The actual energy usage depends on many factors, including the ambient temperature around the Sundanzer, the ambient temperature around the batteries, the thermostat setting, what you're trying to cool, etc. But hopefully my example will give you some figures to play with.

With the AC/DC option, the Sundanzer can run off AC or DC (typically a deep cycle battery or battery bank, which you supply and is external to the unit). The Sundanzer will use DC as a backup, automatically switching to your batteries if the AC goes out (or was never used in the first place). It won't charge the batteries so you'll still need a battery charger (or charge controller if you're using solar). Note that even if you plan to run this with a solar panel, you'll still need a battery in the equation; the Danfloss compressor needs in-rush amps that panels can't supply. And of course solar isn't possible at night. Photovoltaics, then, are really about charging the battery--not directly running the unit per se.

Physically, the unit is solid although not exactly industrial. It has the thickest walls (most insulation) of any fridge I've ever seen, which no doubt contributes to its impressive efficiency. Inside, the baskets work well and really help with organizing. Under the hood, those who like tinkering with electromechanical things will find that the Sundanzer is very amenable to that, and it wouldn't be difficult to integrate one into a home automation system. The electronics are simple and overengineered--eschewing delicate boards that can be fried by a simple static shock.

Overall, this is a very bare-bones unit, and the entire Sundanzer line could use a refresh. For example, the single control--a plastic knob for the aforementioned analog thermostat--feels cheap and primitive. A digital thermostat capable of spanning a large range would allow the unit to function as a fridge or freezer. An LED display could tell you what the internal temperature is without having to open the unit. I'd also prefer a hasp or lockable latch to the current plastic lip.

As mentioned in other reviews, another downside is the unusual 24-volt 7-watt incandescent bulb. The bulb base appears to be a type E14 (14mm base) SES (small Edison screw), which is the type Europeans might use as nightlights near their beds. True, it only consumes 7 watts, but that's not so impressive given the meager light output. I've seen LED flashlights that are orders of magnitude brighter at a fraction of the wattage. A premium and expensive power-saving product such as the Sundanzer really ought to use LED technology.

While the Sundanzer is not fancy, it is reliable, and there are few other products like it on the market (Engel and SunFrost being the obvious competition). It's also a very flexible product; you can start off using it just like any other fridge/freezer, running it off standard household AC; no batteries or photovoltaics are needed in this configuration. Later, when you're ready, you can explore the DC option, perhaps as part of a series of ongoing steps to reduce your dependence on the grid. Its ability to handle both 12 and 24 VDC is another testament to its flexibility, and one that you'll particularly appreciate if, like so many, you start off with a 12-volt system and later realize that you've outgrown the wattage restrictions due to the unmanageable amperages involved in delivering those watts.