We don’t realize how much we depend on our refrigerators… until there is a power outage.
The upsurge in widespread wind damage, flooding and forest fires with resulting extended power outages has not gone unnoticed. Homeowners have increasing interest in attaining energy independence from an electrical grid susceptible to extended power outages. Because whole house solar is cost prohibitive in the the states that do not have solar incentives, “stand alone” solar powered refrigeration with battery backup is a good option.
You may have thought about installing some solar panels, a battery, cabling and just running your current refrigerator on a small stand-alone solar setup. Unfortunately, it’s not practical because conventional residential refrigerators are manufactured to run only on AC (alternating current – the type of electricity power companies provide). Refrigerators made to run on AC are impractical for stand-alone solar because they draw a tremendous amount of power during the moment the compressor cycles on, IE about four times (4x) more power than a DC (direct current) refrigerator. To operate they need significantly more solar panels to collect the suns energy and significantly more battery backup than a DC refrigerator. Click on this link if you’d like to read about alternating current, vs direct current.
Solar panels generate electricity as DC (direct current) which is then stored in and distributed from batteries as DC. Energy efficiency is why DC refrigerators are much better suited for solar applications. It’s one of the main reasons DC fridges are universally used in the RV and boating community. DC fridges made specifically for use in a RV or boat most often have less insulation in the sidewalls because they’re built to fit in very tight spaces. You are going to want the best insulated refrigeration possible for a solar application, so getting a wall-unit RV fridge for your kitchen isn’t the solution.
Why DC refrigerators cost more
DC refrigerators for residential use are more expensive than comparably sized AC fridges partly because their side walls are constructed to have thicker insulation than a conventional AC refrigerator. Another reason for the higher cost has to with their much smaller market share.
The two largest local solar companies here in North Central Florida only do whole house solar installations which are at least 5 kilowatt (5,000 watt), and will not install a small system for just a DC fridge. Do-it-yourself installations of small solar setups have also been limited because the many possible options and variables (even in a small system) can seem confusing to non-professionals. Your electrician may or may not be familiar with installing with a DC solar setup, but if they have ever installed a solar operated gate – its the same principle.
It’s unrealistic to get a one-size-fits-all solar component package and expect to have exactly what you need for a solar powered refrigerator installation. It is smart to rely on the expertise of a reputable solar supply company to help determine the right solar components based on the specifications of the DC fridge selected and then order directly from them.
As of right now residential DC fridges cost about twice as much as comparably sized AC fridges. A DC refrigerator and/or freezer ranges from about $800 to $1,900 depending on size. A stand-alone solar power system to supply DC electricity (consisting of a solar panel, battery backup, a charge controller, and special DC cabling) costs in the range of $500 to $1,000. Installation by an electrician should run approximately $500. In total, installing a solar-powered DC refrigerator would cost in a range from $1,500 to over $3,000 depending on size of the refrigeration unit.
The cost of installing a solar powered DC refrigerator vs. whole house solar
In states without solar incentives the majority of homes do not have a whole house solar system (with or without battery backup). Whole house solar with battery backup costs upwards of $25,000.
Conventional AC refrigerators use about 8% of the total electric of a typical home (without a pool or spa). At current rates for electric, they are not very expensive to run, only about $100 per year. Calculate the annual cost to run your refrigerator. Having a solar powered DC fridge would save only about $100 or so off your electric bills annually. However, when we calculate that 8% of $25,000 is $2,000, then the price of solar-powered refrigeration seems more within reason.
As demand for residential solar powered DC refrigerators increases their prices should come down. So if buying one is not in your budget, keep checking back because with increasing climate uncertainty and power supply interruptions the demand for solar powered DC refrigerators is going up. On the other hand, if having functional refrigeration during a potential extended power outage seems worth the investment at this juncture, there still is one more consideration:
Fridge size matters
DC refrigerators available for the residential US market come in a smaller range of sizes – from 4 cu. ft. to a little over 15 cu ft. Conventional AC refrigerators range in size from 10 cu ft (apartment size) to about 30 cu ft (large family size). As a point of reference, a typical three bedroom home would likely have a 17-18 cu ft AC refrigerator. Refrigerator retailers in the US market recommend 4 to 6 cubic feet (cu. ft.) of refrigerator space per adult in your household. My daughter has a family of four. Their current fridge is 19 cu. ft. There is quite a bit of open space and they could do fine with a 40-50% smaller fridge. Bottom line: Whether operating an AC or DC fridge, the bigger the refrigerator the more energy it consumes to keep cold.
When considering getting a solar DC refrigerator it’s VERY IMPORTANT to determine if you will use it only during an extended power outage, or year round. If you intend to install a solar fridge for full time use, then an adequate sized DC fridge with freezer to replace your existing fridge would be the logical choice. However, if you only intend to use it as back-up for when the grid is down then consider getting a DC freezer. They are available as cabinets or coolers, both which have a hinged lid and are accessed through the top. During an extended power outage you can make the ice needed to replenish well insulated (non-electric) coolers. The cooler type chests have settings so it can for refrigeration and/or freezing, are portable, and can be operated from a vehicle adapter.
DC fridges will run on stand-alone solar using one correctly sized solar panel, one deep cycle 12v battery with an adequate amp-hour rating, and a charge controller. We recommend having a solar professional plan out the size solar panel needed (in watts) and the capacity (in amp-hours) of the deep cycle battery based on regional climate (IE: mostly sunny or mostly cloudy); and also help you plan for enough capacity for a few days without full sun due to extended cloudiness or forest fire smoke.
DYIers: Here is an informative article: Installing your own small off grid solar system. Two things we would add: One is to be sure to get batteries with a high enough amp-hour rating to provide power through a series cloudy days. In Florida we plan for having 4 cloudy days in a row where the solar array will be collecting only about 10 to 25% of the energy it would normally collect on a sunny day. Lastly, you may want to look into purchasing a charge controller with MPPT + equalization as those features will increase battery efficiency and battery lifespan thus reduce the component sizes needed and reduce battery replacement frequency.
Having an energy independent refrigerator is excellent preparation to have done in advance of the next power outage.
Pick up this comprehensive resource (240 pages): Lights On: The Non-technical Guide to Battery Power When the Grid Goes Down
Following the simple plans in Lights On will ensure that you are safe and secure during widespread long-term power outages. The US electric grid is at greater risk today than ever before. From aging infrastructure, severe weather, and EPA mandated closure of coal-fired power plants to solar storms, digital sabotage, terrorism, and electromagnetic pulse attacks, future outages are almost certain. And they will likely last far longer and cover much larger areas than anything experienced in the past. When the grid is down and you run out of fuel for your generator, and all the stores are closed, then what? Lights On has the solution. Energy expert Jeffrey Yago lays out the lost history of early residential battery power and delves into just how durable and universal battery-powered devices are. Battery-powered devices can provide lighting, communications, refrigeration, safety, and entertainment when all else fails. Yago covers the multiple ways to keep your batteries recharged and ready to go. Lights On provides easy-to-understand detailed information on having a plan of action for setting up a battery-powered home in advance of widespread and sustained power outages. This is the only book you need to be prepared to keep your refrigerator running, your lights on, and much more.
How much “juice” for your kitchen? March 5th, 2018 – “(AC) Refrigerators use about 8% of a typical household’s electric consumption.”
Solar-powered refrigerators December 2006, By Jeffrey Yago, P.E., CEM – Jeff has over 30 years experience installing solar systems.
First Off-Grid Solar Freezer (for Dummies) June 2014, by Peak Prosperity blogger “sand_puppy”
Solar DC Refrigerator Vs. AC Refrigerator November 15, 2015 – “If you want something powered independently from the grid, then absolutely choose DC.”