There are two types of freezers used in off-grid living.
The two types of freezers used are gas powered or DC powered. Both are produced with a high insulation value to create the best efficiency. The major considerations between a Propane Gas Freezer and a DC Electric Freezer are initial cost and availability of the power source. The power source being DC, propane gas, or natural gas.
If solar energy, wind energy, or hydro energy is available or a possibly at your location, then the DC electric freezer initial cost will be low and this will be the best choice. If none of these DC energy sources are available and purchasing the equipment to capture the DC Electricity is necessary, then the initial cost of the DC unit can easily double. The freezer must have power available at all times to keep the food storage at good freezing temperatures. This usually means that these freezers will require a battery bank for power storage during night in the case of solar powered, or when the wind is not blowing in the case of wind generated power. In some cases of hydro power, batteries may not be needed. Solar power is not free. Solar power requires batteries and batteries do wear out and must be replaced. This must be considered when doing cost analysis.
This is where the possibility of a gas freezer may be best. Gas Freezers can operate from stored LPG (Propane) gas or piped in Natural Gas. In some cases, a natural gas well is available on the property site and a natural gas freezer would be ideal. An un-metered well means free power to the natural gas freezer. Propane gas is supplied either by truck to a permanent tank on the property or smaller portable tanks that can be transported and filled at a filling site. Permanent tanks are available in a variety of sizes ranging from 100 gallons to over 1000 gallons. The freezer can operate from any size tank. The question is, for how long. It is typical for a propane freezer to use approximately 2 to 3 gallons of LPG per 7 days.
What are some of the other differences? Performance, portability, and availability.
Performance between a DC powered or compressor driven unit versus a Gas Freezer or absorption system unit are only different in what is called “recovery times”. This is the time it takes for the temperatures to come down or recover to the thermostat set temperature. Both types will get as cold as one another, but the compressor driven unit has the advantage in recovery speed. It is estimated to be four times faster than that of an absorption freezer.
If you open the door or lid of either freezer to retrieve some food goods then the recovery times will only be minutes for either unit. In this case the differences between the two types is of not much concern. When putting non frozen goods into the freezer, this is when the difference of recovery speed shows up. The greatest difference of recovery speed shows when the units are started up from an ambient air temperature state. A typical chill down time for a DC Solar Freezer will be approximately 2 hours whereas the propane gas freezer may take up to 8 hours.
Both units can be portable. The Propane Gas Freezer is very portable due to the nature of the propane being in tanks. The DC freezer is also portable if the unit is operated by a portable power source such as batteries of a vehicle or a small solar system. The weight of the unit is another consideration. Gas freezers are heavier by at least 80 lbs. due to the absorption system weight.
Currently there is a very limited number of manufactures for both types. The DC Solar Freezers are available from a handful of manufacturers and only in chest style. The gas absorption freezers are only available from one manufacturer and only in upright configuration.
This brings up the last comparison. Chest style versus upright style. There are two arguments. You can decide which makes more sense. Chest style units do not allow as much cold air to escape since the lid is opening at the top and cold air falls. Upright freezers are usually open for less time since the goods are staring you in the face and are more accessible than the buried goods in the chest style. Furthermore, if the freezer is full of food then there is less air to fall out when the door is opened.