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Solar Energy Isn't Free Energy

One of the things I used to admire about folks who are off-grid is that they have no electric bill. Many of them say it themselves, they love the financial freedom of not having to pay for electricity. Still, we all know there are costs involved, and some people might be inclined to ask how long it will take for the system to pay for itself. A low-end off-grid system might cost roughly $35,000 not including shipping, installation, and interest if buying on credit. Neither does that include backup, i.e. a generator. The average American electric bill is said to be $104 per month. Do the math, and you'll likely agree that it takes more than a monetary advantage to go solar.

For some people it's a sense of environmental responsibility. For Dan and me, the motive is food preservation. Since we rely more on what we grow than on a grocery store, this is important. The cost of a year's worth of groceries more than offsets the system paying for itself. We've spent roughly $2450 on it, so compared to having to buy all of our groceries, our little system will "pay for itself" in about three or four months. Savings on the electric bill will be lagniappe.

Now that we are in the midst of the project, however, I see something I didn't consider during my feasibility study—eventual replacement costs.

Having recently purchased our batteries, this is forefront in my mind. Our solar panels should last 25 to 30 years, but flooded lead acid batteries average about five years; longer if we take good care of them—shorter if we make mistakes. The fact of the matter, is that we have to be ready when they need to be replaced. Our income is low enough that we must budget for everything, so I need to take this into account now.

What am I looking at for replacement cost? Our six batteries totaled $880, with $100 of that for the core charge since we didn't have old batteries to trade in. If the batteries last 5 years, and I want to have $780 available for replacements, then I need to save $13 per month. Because prices always go up instead of down, it would probably be wise to bump that up to $15. If we want to upgrade the battery bank—in terms of battery type, amp-hours, or both—then we need to set aside more.

We could have bought a different type of battery, one with a longer lifespan, but these come with a heftier price tag. As it was, we did the best we could, and I have no complaints about that. I would be curious if the cost per year for different battery types is comparable to $13 a month, but for now, that's a moot point.

Of course, I'm curious about how much lower our electricity bill will be once we get the freezer (and hopefully fridge) on solar. Will it be enough to offset the savings for replacement batteries? Time will tell! Either way, our ability to preserve our harvest without being dependent on the grid gives me great peace of mind. And that, is priceless.