A kilowatt hour seems like a trifling thing. You can consume a kilowatt hour in about 50 minutes with a microwave oven, or five hours with a large television. Over the course of 80 minutes on a treadmill your body can burn a kilowatt hour’s worth of food energyabout four chocolate donuts, or one double cheeseburger. Depending on where you live, it costs more than a quarter or less than a dime. Each year the United States consumes the equivalent of 30,000,000,000,000 kWh of energy, and if your home is tied into the electrical grid, chances are you use up 20 or 30 kWh every day without really having a clear idea of how you do it.
If one day you move off the power grid, however, things will be quite different. You will quickly learn that it takes a $660 solar panel a day in the sun to produce a single kilowatt hour of electricity, meaning that it requires an array of these expensive panels to supply your energy needs. Suddenly, a kilowatt hour becomes a formidable unit of energy.
On the positive side, that same $660 solar panelsomething in the 220-watt range at late 2009 priceswill produce in excess of 14,000 kWh during its lifetime. If we allow that the panel will endure the elements for 40 years (a conservative estimate by most accounts), your upfront cost for the electricity it provides will be less than five cents per kWh, and if all you ever needed for your off-grid system were five or ten solar panels you’d be reckoned a savvy investor.
But solar arrays need to be mounted onto something, whether it be a roof, a deck, or terra firma, which means you’ll need some manner of mounting system. The wattage the array produces will have to travel along a pair of heavy copper wires to the charge controller, batteries, and ultimately the inverter. Along the way it will encounter circuit breakers, disconnects and perhaps a combiner box. All of this stuff adds to the cost of the system and much of it, particularly the batteries, will have to be replaced long before the solar panels expire.
How much will all this cost? To answer this question I asked Scott Gentleman from Backwoods Solar (www.backwoodssolar.com, see their ad on page 21), a catalog-based business that has specialized in complete off-grid systems for homeowners since 1978. According to Scott (who, like everyone else at Backwoods Solar, depends on the products he sells for his own electricity), the general range for starter systems tailored for single-family off-grid homes is $11,000 to $18,000, although he has designed systems costing over $60,000.
“We design most of our systems to provide 4.5 to 5 kWh on days when the sun shines,” Scott told me. That’s a far cry from the 20 to 30 kWh most grid-connected folks are accustomed to, and to many would-be off-gridders it might seem an untenable lifestyle change. And yet I’ve met dozens of families who thrive within these limits. Mostly, it’s a matter of making smart choices when building a home and buying appliances, and nurturing the habit of using energy wisely. The first system my wife and I put together was well within this range, and it served us for many yearsuntil we traded our propane fridge for an electric one, bought a small electric chest freezer, expanded our home-based business and…well, you get the picture. But even after our entrepreneurial pretensions and shameless indulgences into state-of-the-art food-preservation technologies, our energy consumption rarely exceeds seven kilowatt hours per day.
But back to Scott and the systems he sells. To see what I’d be getting for my money, I asked Scott to work up a quote for a starter system suitable for, in his words, an “active family.” The heart of the 24-volt system he designed includes six of the above-mentioned 220-watt solar panels with a pole mounting system (minus the pole); an OutBack custom power center built around a 3,500-watt sine-wave inverter and a 60-amp MPPT charge controller; eight Trojan L-16 batteries, and various other goodies. The price for this system was $13,825. Not bad, considering it’s all top-of-the-line equipment and components.
Not included in the price were shipping and pretty much anything that can be acquired locally, such as steel pipe, wire, conduit, concrete, grounding rods, etc. And, of course, the labor and expertise to put it all together. Bottom line: to be safe, figure $18,000 if you do the work yourself; maybe $20,000 if you hire it done. If you want a good backup generator (and trust me, you really, really do), add another $3,000 to 4,000 (though you can certainly spend a lot more if you have an inkling to).
How much energy will this system produce? In our home state of Colorado, a place where the air is thin and the sun persistent, this system would, on average, crank out around 6.5 kWh/day. In the arid Southwest it would easily top 7 kWh/day, while in most of the Midwest the magic number would be closer to 5 kWh/day, with production diminishing as you move north and east. Without getting too deeply mired in statistics, then, this system should easily average 5 kWh/day in most locales.
Next, we have to make some assumptions regarding the lifetime costs of the system and its components. Allowing that you’re a fastidious person and you take excellent care of your things, in the course of 40 years you can still expect to go through five sets of batteries, two inverters and charge controllers, and probably two generators. And since I know you’ll be tempted to, we should also assume that you will, like we did, upgrade your system within the first few years. (See chart above.)
What do you get for $53,640? Approximately 73,000 kWh of quiet, pollution-free electricity at a cost of $0.73 per kilowatt hourhardly the bargain price of $0.05/kWh we started with, back before things got so complicated. But before you rip this magazine into tiny pieces and vociferously declare that only a complete idiot would choose to live off grid, there are other factors to consider. For starters, there are avoided costs, such as the cost of the grid power you would have paid for but didn’t, and the expense you would have incurred to have utility power run to your remote site, had you not decided to live off grid.
The first of these considerations lowers your bottom line by around $35,000, or 20 kWh/day @ 12¢ kWh (the national average) for the electricity you won’t be buying from the local utility for the next 40 years. As for the second consideration, figure at least $12,000 if your site is over a quarter mile from the nearest power pole.
Additionally, there are federal tax credits to lower your upfront costs. Provisions in the American Recovery and Reinvestment Act of 2009 allow you to deduct 30 percent of your total system cost (and the system upgrade) from the bottom line of your tax return, saving you $6,600.
Making the necessary subtractions:
The revised analysis (which I readily admit is hardly exhaustive) is what it will cost you to live off the grid for 40 years, over and above what it would cost to live connected to grid. As you can see, it’s essentially a wash, and it means that you can enjoy off-grid independence and a lifetime without power failures for the same amount of money it would take to hook into a persnickety power grid.
Of course, calculating anything over the span of 40 years is a fool’s errand (which explains why the government is so fond of doing it). It could very well turn out that rising energy costs sweeten your off-grid investment beyond your wildest dreams. Then again, you might decide to move off grid the first year of a 40-year cloudy spell.
But however it works out, you’ll never again take a kilowatt hour for granted.
Rex Ewing is the author of several renewable energy books, including Power With Nature, Got Sun? Go Solar, and the newly released Crafting Log Homes Solar Style. He lives with his wife, LaVonne, in a handcrafted log home powered solely by the sun and wind in the foothills of Colorado. His books can be purchased at the Countryside Bookstore.