More Musings of an Energy Nerd
While my wife and I were away on a recent vacation, my brother was house-sitting at our off-grid home in Vermont. Halfway into our vacation, my brother emailed me to let me know that our inverter had died. (An inverter is an electronic device that produces AC electricity when hooked up to a battery.)
After a local solar contractor visited the house and confirmed that our inverter was shot, my brother managed to limp through the next few days by running our gasoline-powered Honda generator for most of the time. It was nip and tuck, but he kept the house going (and our refrigerator cold) until our return.
Once we got back from our vacation, I spent a little over $3,000 for a new inverter and various electrical parts. I took advantage of our inverter’s demise to upgrade the system from 12 volts DC to 24 volts DC. Since our battery has 12 cells, the voltage change didn’t require us to buy a new battery; all I had to do was rewire the cells (and the PV arrays, of course).
The process was multi-staged and laborious. Suffice it to say that I spent many days rewiring the house. Among the new pieces of equipment I had to install was a 24 volt DC to 12 volt DC transformer to handle our home’s DC loads.
I was lucky. While many people who live in an off-grid house can’t do their own wiring, I can. I probably saved several thousand dollars in installation costs by doing my own wiring. That said, our lifestyle was altered during the week of repairs; we turned the generator off when we went to sleep at night, so it was handy to have a flashlight to find the bathroom.
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29 Comments
I think "the deal with resiliency" came about because Rick Perry came out with his proposal to subsidize coal and nuclear plants, conflating "resiliency" with fuel-on-site.
I agree with getting to know your neighbors, borrowing and lending a hand or a cup of sugar and developing relationships.
Being on grid while having a PV array and a small battery backup, sufficient to run a fridge and a few lights and charge phones if you need to operate as an island, also adds resilience.
"And if you want your lifestyle to be more resilient, you don’t need to buy $20,000 of new equipment for your home. You need to get friendly with your neighbors. What we need to get through our coming crises is improved social ties."
I think you're developing a false dichotomy here...
Ethan,
If my writing implied a dichotomy, that wasn't my intent.
My intent was to inform those tempted to invest $20,000 in "resiliency gadgets" that they are likely to be disappointed by these investments, and to note that the likely results of good social ties with one's neighbors are many times more satisfying and productive.
With our climate changing, we face an uncertain future. I think that some "resiliency" experts are giving bad advice. For a further discussion of these issues, see "When the Gas Pipeline Shuts Down."
Martin, Thanks for your reply. From a linguistic point of view, I believe the statement I quoted is a clear example of a dichotomy ("A separation or division into two; a distinction that results in such a division. " - Wiktionary).
That being said, I understand your point, and believe that some blending of the two is worthwhile - maybe communal resiliency. Perhaps I misread your quote because you allowed me to fill in my $20,000 resiliency wish-list. I wholeheartedly agree with you that interpersonal and community relationships are vital.
I also believe that there are certain constructed (and purchased) methods of resiliency (insulation, good tools, wood stoves, rainwater harvesting) that are good investments and are not mutually exclusive from building a strong community.
I think what gets my hackles raised by quotes such as yours - is that people are right now out spending $20,000 on new cars, European vacations, etc. People are dropping $20,000 on online masters degrees! So I don't see the point in dissuading people from making investments in a comfortable low/no energy future.
For example, one takeaway I got from the Armenia story is that an efficient, portable, clean heater, as well as insulation would be a good investment for the future.
For example, I have one of these: https://ecozoom.com/products/zoom-versa
Re: getting to know your neighbors. I live in a small town in Maine. Yesterday was very windy and cold. Power was out for a couple of hours. Anyway, we went to a local orchard for cider and apples. On the way home, the car in front of us stopped suddenly in the middle of the road. A big dead tree had broken and it fell across the entire road. Within a few minutes, four or five vehicles stopped. Without anyone saying a word, we all got out and dragged the heavy tree onto the shoulder, picked up the branches still in the road and were on our way. The woman in front of us lived a very short distance away. She went home to get a broom to finish the cleanup.
Stephen,
On my road in Vermont, wind storms usually drop a few trees onto the road. Those of us on the road who own chainsaws know this, and we put a chainsaw in the vehicle when we drive down the road after a stormy night. The first chainsaw to arrive at a downed tree clears the road. A few neighbors don't have chainsaws -- they usually wait patiently for one of us to show up and cut up the tree. (Or show up at our door to drink a cup of coffee until we go down to the tree together.)
Stephen and Martin - Those are great stories, and I think many of us share the value you place on community - cooperation, friendship, etc. But I still don't see how these values preclude technical responses to carbon
Ironically, when you listed your $20,000 price tag, one thing I thought of was a new chainsaw and tools to cut up wood. Someone has to have the tools to share... and someone has to lead the way when it comes to building comfort and efficiency upgrades.
Ethan,
I believe in having good tools that you use regularly. Some investments in "resilience," though, are features that aren't used daily -- they are planning for an apocalypse. And the thing about the next apocalypse is that it probably won't look anything like the last apocalypse.
If you need a steel stove that drips used motor oil on unnecessary books you're willing to burn, by all means get an Armenian-style stove. But I don't think you should buy that type of stove if you don't need one right now.
An off-grid system? A big cistern to store rainwater? Maybe -- if you need them now. Otherwise, I'd hold off on the hardware purchases.
There is another aspect to this. It's one thing for enthusiasts to discuss adding and maintaining the equipment and technology to go off-grid, but we know from experience that the pool of people willing to do even basic maintenance and repairs to our existing low-tech housing stock is very small.
So this change would necessitate a whole new industry being established to keep these individual self-powered houses going. Then it begs the question: If these houses rely on outside help, and are increasingly controlled by networked controls, how resilient are they?
Martin,
You must live far enough out of the way that no inspectors had to show up and bless your rewiring. Where I live, you would have gone to get a permit and had a code compliance inspection.
Thank you for this. I've always appreciated your candidness about life off the grid.
It's worth pointing out here that "the grid" is essentially community (working with your neighbors). Even with modern technological advancements it is still almost certainly the most cost effective way of providing water, sewer, and electricity above a certain population density. Where the grid is failing us it's probably because we're failing to invest in necessary maintenance and improvement. I would completely contradict Mr. Lstiburek in that I think the grid works so well in most of our country that people take it for granted, to the point that maintenance and improvement costs look like unnecessary expenses.
For the record, how old was the inverter that died?
I agree with you, Martin. I will add that Dr. Joe seems to be comparing the present to a fantasy of 'the good old days', which is probably inaccurate for most people. As Martin says, the calculation varies with location, but in many places in the US and Canada, more people have more reliable water and electricity than did their parents and grandparents. From the US perspective, his faulting of 'the government' is misplaced, since electricity is dominated by private enterprise mixed with convoluted government partnerships and regulations. On the other hand, I would love to see government and infrastructure both improve, which will require voters to vote more intelligently.
Guys, I'm sorry but the curmudgeonly outlook in this thread will finally drive me to cancel my subscription. Why continually question others' motivation for design improvements, rather than address these designs on their own merit?
How can you dismiss anyone outside of Flint for wondering about their water supply? Just across the river from me an entire community is questioning the safety of their water supply (https://www.cityofnewburgh-ny.gov/water-department/pages/2016-pfos-contamination-water-crisis-update).
I came here to this website to discuss Green Building, which I know has many definitions to many people... I believe these all could be welcomed.
I did not come here to get a reprise of Mr. Rogers Neighborhood.
Perhaps a more nuanced discussion of scale jumping - resiliency at a community level - might be interesting. Instead we get scolded for contemplating anything ... other than what? For the life of me I don't know. Maybe a grid-connected pretty good home is all that is acceptable here? Even this will be filled with a few high tech gadgets...
If the pinnacle of Green Building that can be dreamed up here is lending your neighbor a chainsaw... maybe I'm in the wrong place. Acquaintances of mine are currently building a energy hog mansion up on a hill. I'm sure they'll have a bunch of gadgets... and I'm sure most of these gadgets won't work when the power is out. Is this better? Is this worse? Does it matter? I'm sure they'll lend me a tool if I need it... But do I think they should downsize, insulate better, and... egads... install a cistern!?! Yes! Is theirs in any way imaginable going to be a "Green" home - whether they lend me tools or not - NO!
The fallacy of the complaints about "high-tech" sustainability/resiliency/green solutions is that they are so often blind to the "high-tech" gadgetry which is propping up the dominant/conventional version of the modern built environment.
If I was confident that there was a lot of information here on GBA regarding low-tech solutions or alternatives to the Foam+Plywood+ERV+Minisplit way of putting a pretty good home together, I would find the criticism posed here to have merit. But I see little of it. So the narrow window of acceptable practice instead seems unnecessarily confining. Thanks for all your assistance regarding air sealing, proper insulation, etc. I think just a little dose of Treehugger.com is needed over here.
Ethan,
Construction is a conservative industry. Sometimes out of self-interest, sometimes as a reaction to past experience where adopting new approaches has lead to widespread envelope failure, and sometimes because the consequences of the failures can be the financial ruin of the builder.
I guess we are all looking for something different from this site. I'm encouraged by any consensus that emerges as to how we should be building. I see a narrowing of options as eliminating unviable approaches. I don't think an industry where everyone starts from scratch and individually designs each part of envelope is useful or viable way of proceeding. If two or three alternatives emerge as dominant for each climate zone that would seem to me to be a good thing.
I didn't take Martin's description of being off-grid as an injunction to abandon resiliency, but rather a realistic look at the consequences of being self-reliant. My own house relies on low-tech to try and build-in the resiliency necessary for its rural setting and the twenty+ power-outages we have each year. I'm happy knowing there is nothing I can't easily fix myself, but at the same time find it tiring to always be on call to step in and keep the place functioning. When the grid comes back up I'm grateful and happy I can continue to benefit from such collective endeavours.
Ethan,
I certainly hope you don't cancel your subscription to GBA. This site has all kinds of articles, most of which are practical. We also occasionally publish opinion pieces (where a wide variety of opinions are expressed).
I don't think that anyone has scolded you. The site provides examples of, and advice on, community-scale solutions as well as individual solutions to technical problems. And I think that all kinds of gadget advice is available here.
Don't be scared away by one opinion piece! I think you'll find that the GBA tent is wide enough to include you.
Response to Antonio Oliver (Comment #10):
Q. "You must live far enough out of the way that no inspectors had to show up and bless your rewiring."
A. Yes, that's right.
Response to Andy Kosick (Comment #11):
Andy,
You wrote, "It's worth pointing out here that 'the grid' is essentially community (working with your neighbors)."
I agree completely. If one house has a PV system that is producing more electricity than that house needs at any particular time, it certainly makes sense to share that extra power with a neighbor who needs it -- and to have an accounting system that fairly allocates costs and credits. (That last part can be tricky, but it's doable.) The grid is far more efficient than batteries.
Q. "How old was the inverter that died?"
A. I bought the inverter (an Outback model FX2012) on July 15, 2010. It died in early August 2018, when it was 8 years old.
Thanks for the info on your inverter, Martin. If you ever have time (ha!), a break down of the equipment you've purchased over the years with costing would be appreciated. I always, personally, find "real world user's" experiences in regards to "fringe" technology quite illuminating. Sometimes it's not so fringe--sometimes it is.
Jaccen,
I can't break down the cost of all of the electrical equipment I've bought over the years, but I can let you know that these days, most off-grid electrical systems cost in the range of $30,000 to $40,000. It's certainly possible to do it for less, especially if you are planning a simple lifestyle and can do your own installation.
Most analyses I have seen show that off-grid electricity costs between 50 cents and $1 per kWh, with much of the cost associated with generator costs (and associated fuel) and battery replacement costs.
My most recent inverter cost $1,875, not counting associated meters, electrical boxes, and disconnects.
Over the years, I've owned at least three Honda generators; these generators have cost me between $1,800 and $2,100 each. Fuel costs per month are high during the months of November, December, and January.
Martin,
Can you recommend a website, authority, or document for information on how much energy one could expect a PV system to produce (perhaps on a per panel or per unit area of solar collection or some usable unit) in its lifetime? I'd like to get an idea what the $ per unit of energy looks like instead of the $ per Watt. Most analyses I've seen do comparisons in units of power instead of energy.
Antonio,
The PVwatts calculator (maintained by NREL) does an excellent job of estimating the annual output of any PV array. You can expect a PV array to last at least 30 years.
PV modules are relatively cheap. The expensive parts of an off-grid system are the batteries, the generator, and the fuel associated with running the generator.
For more information, see:
"An Introduction to Photovoltaic Systems"
"How to Design an Off-Grid House"
"Batteries for Off-Grid Homes"
Martin,
Thanks for this write-up. A little perspective is always welcome, since some of us GBA readers may have a proclivity to embrace gadgetry without necessarily thinking through whether our goals (both individual and community) could be accomplished more simply. More to the point, most of the progress toward a sustainable future will be made by people deciding not to buy stuff, rather than by buying "green" stuff - especially here in the wealthy U.S.
That said, I suspect your estimates for off-grid costs are a little high in these times of rapidly falling prices. To add to the discussion, let me provide a little hypothetical.
A system with a 9 kW nameplate capacity (30 panels at 300W each) can be expected to produce about 15 kWh/day in the depths of winter, and close to 40 kWh/day at the height of summer: enough to supply all the needs of a pretty efficient household with supplemental heat (I prefer wood, but that's a whole 'nuther kettle of fish). Total annual output is for this 9 kW system is around 10,800 kWh in my neck of the woods (northern Indiana).
That system runs about $20,000 these days, including about $9k for what I’ll call the “power center”: a 8-9 kW inverter with enough juice to power an entire family home, charge controllers sufficient for all those panels, a user interface and associated bits and pieces. Add another $20,000 for a modern lithium battery bank with 20 kWh capacity, which should be enough to avoid excessive (or perhaps any) generator use most of the year.
Assume lifecycles of 30 years for the panels, 10 years for the battery, and 8 years for the power center. All pretty conservative, I think (note that lithium batteries are rated for ~5,000 cycles even at 80% depth-of-discharge, and some are warranteed for 10 years).
So, adding it all up over a 30-year span: $20k (initial system) + $20k (initial battery) + $20k (replacement battery @ 10 years) + $20k (replacement battery @ 20 years) + $9k (replacement power system @ 8 years) + $9k (replacement power system @ 16 years) + $9k (replacement power system @ 24 years) = $107k over 30 years or about $3,570 per year. This adds up to 33 cents/kWh. This is without any government subsidy; today, of course, you can knock at least 30% off that total if you pay federal taxes. On the other hand, I haven't included labor costs or installer margins, which of course can increase the spend significantly.
The actual 30-year cost might be lower because:
- Lithium batteries will almost certainly get much cheaper over the 30-year period, and indeed they are already doing so;
- The cost of solar panels will probably continue to fall as well;
- The entire power system probably doesn’t need replacement every 8 years, and the last one purchased in my 30-year hypothetical still has half its value left at the end of the 30-year period above;
- Other parts should come down at least modestly in cost as solar systems gain more widespread adoption and economies of scale are realized.
All that said, I agree with your premise: resiliency is found in community first and foremost. No one is an island, nor should they be: we are a social species and are generally happiest when we are engaged with our neighbors. Moreover, to realize the 33 cents/kWh number I cited above, one has to use all the energy produced. That’s a lot easier to do (especially in summer) when you can share overproduction with your neighbors via some kind of shared electrical infrastructure (e.g., a grid). Otherwise, energy "spilled" by the off-grid system could easily drive the cost up, say, 30%. That's still not 50 cents, though, and nowhere near a buck.
My bottom line: I would not go as far as to counsel my neighbors to avoid installing an off-grid solar system for purposes of resilience. Part of being a good neighbor is maintaining some spare capacity, if you can afford it, that you can use in times of crisis to help both yourself and your community. Whether that comes in the form of a big garden which produces more food than the family needs, or a big solar system that produces all of the family’s power and then some, these are valuable assets to be shared in times of need.
Getting back to the off-grid solar system, there’s a way to manifest this principle in the here-and-now: stay connected and let the system be “off-grid-capable.” Share the overage with your neighbors via the grid, even if (as in my state) you get paid peanuts by the power company to do so.
Brian,
You have pointed out two weaknesses in your economic analysis: It doesn't include installation costs, and it assumes that 100% of the electricity produced by an off-grid PV array is used. (That's impossible. In summer, much of the electricity goes to waste.)
Here are two more weaknesses: you have budgeted zero dollars for repairs and maintenance; and you have failed to account for the costs of a purchasing a generator to make electricity in November, December, and January, and 30 years worth of fuel. (Have you tried to limp through an Indiana winter without a generator? If you've really done it -- without candles or kerosene lamps -- congratulations. If you haven't, you're probably guilty of a inventing a paper-based fantasy scenario.)
Here in northern Vermont, an off-grid PV system won't get you through the winter months without a fossil-fuel generator. Not going to happen.
Well, it doesn't get much tougher than northern VT to make the economics pencil out. In Northern Indiana, it's a bit easier. Bear with me while I shepherd us a little further down the rabbit hole and let's see if we can get to an all-in number that's closer to reality than fantasy.
For labor let’s assume $20,000 in installer costs and margins for the initial system and $1000 for each of the five replacement jobs. (Full disclosure: I’m an installer.) These numbers are a little generous but reasonable. Total: $25k
Other repair costs are harder to estimate, and I can't see what other repairs can be expected outside of storm damage, etc which would presumably be covered by insurance. Let’s toss in another $2,000 and call it “miscellaneous” to account for deductibles and other small issues.
Let’s further assume an average of 30% energy spillage for the sunny half of the year, though this will be highly owner-dependent. In warmer climates, the cooling load can use up quite a bit of the summer production.
As to generators, I agree that an off-grid homeowner would be in the dark at least occasionally without one, and many homeowners have one anyway for other tasks. I believe it’s more cost-effective to minimize genset use by oversizing the array as needed. You can buy a lot of solar capacity for $6,000 worth of generators and 30 years of significant fuel use. The 9 kW system in my comment above can produce 6 or 7 kWh on a cloudy and short Indiana winter day, which is enough for lighting and a few extras.
A $1000, 2 kW Honda generator should be sufficient to power the house if it is used to charge batteries (letting the inverter handle peak loads) rather than powering loads directly. Remember we are designing for 15 kWh/day in winter; that's easily met with a 2 kW generator supplementing whatever solar you can scrounge.
If the above-mentioned average deep-winter production of 15 kWh/day is enough to meet the average need (which is our design assumption, and a fair one for efficient homes), the generator is only needed for the occasional long stretch of bad weather. Fuel costs and generator use should be negligible; if they aren’t, the system should have more panels. Let’s plan for $4,000 over 30 years to account for light use of two small Hondas.
Plug it all in, and you get to an average annual usage of 9180 kWh for $138k over 30 years, which brings you right up to 50 cents per kWh, all-in. I can’t see how this system, over the next 30 years, could exceed this number on any reasonable set of assumptions. I suppose very low summertime energy use (as in, at or below the levels of winter use) could drive up the number. I’m happy to be corrected if my assumptions are wrong, or I’m missing something. And of course, we could build in more assumptions - the time value of money, prospective increases in grid costs and traditional generation, etc. The mind boggles, and the next 30 years are sure to challenge all sorts of assumptions. But I think I'm in the right ballpark.
But if we're trying to be complete, we should include that 30% subsidy for the original purchase (true) and make some modest assumptions for cost reductions over time (likely): lifetime costs drop to 43 cents. Call that “hopeful.” Assume the federal subsidies remain intact and steeper cost reductions and 31 cents is on the menu. Now we are getting a little closer to “fantasy!"
Brian,
OK, you are up to 50 cents per kWh, which is within the range of costs I discussed. I think your assumptions about generator use are unrealistic, and I also think that your assumption that 100% of summertime PV production will be used rather than wasted is absurd (especially if you oversize the PV array for winter). [Later edit: My mistake. I see that you have accounted for the fact that some summertime electrical production is wasted.]
One more observation: If you assume that your estimate of 50 cents per kWh for the $40,000 system you describe is correct -- I don't, because I think it is low -- it is only reasonable to conclude that the cost of electricity for a smaller (more typical) off-grid electrical system will be higher -- that is, more than 50 cents per kWh -- due to efficiencies of scale.
On a very basic point, however, we agree: off-grid electricity is significantly more expensive than grid electricity.
And I'm still waiting to hear from an off-grid person who lives in Indiana, so that we can hear about wintertime generator use from a veteran.
Martin,
Look again - I shaved 15% off the annual production number to account for summer energy waste (that's the reference to 30% spillage for the sunny half of the year). This was one of the assumptions got me to 50 cents. Maybe that's a low estimate of waste, but I don't think so - at least not for a house that uses at least some air conditioning (and around here, that's the vast majority).
That leaves generator use as the only bone of contention - stay tuned, winter is coming! Our house remains on the grid, so I can share summertime overages with my neighbors. But, it will be easy to figure out how much generator use would have been needed to substitute for our grid use in the coming months.
Cheers!
Martin and All
I have been following this conversation with interest. Like Martin I have lived in an off grid home for nearly 40 years and have experienced directly the remarkable evolution of renewable energy systems in those years. We also have invested in numerous replacements and upgrades of panels ,batteries and inverters over the years and don't have an accurate record of all the associated cost involved in our systems over the years but is certainly fair to say we have paid a premium for a often limited amount of electricity especially in the early years. Our first system was 2 Solerex panels and a single 12v deep cycle battery in 1979 .In those days we used Aladdin lamps, an outhouse, hauled water from a neighbor and heated with wood, cooked with propane in the summer and on a wood fired range in the winter. Like almost anyone who has had to depend on gas fired generators for essential (or what we perceive as essential) services I spent way too many cold Central Wisconsin winter mornings and evenings negotiating with internal combustion engines.
Our system has evolved in scale and quality over the years and is now a roof mounted PV array with peak output of about 3K and a small 700 watt windgenerator on a modest 70' tower. We have a heavy industrial scale lead acid battery which cost about 6K 12 years ago.
We operate 2 AC chest freezers and a refrigerator, all lighting and electronics, deep well water pump, vacuum cleaner, clothes washer ,electric bikes for some commuting. We still primarily heat with wood and solar thermal.
It's fair to say that generally our guests are not particularly aware that we are not grid tied. It is almost a sure thing that once or twice a year on or about December 25 with a week or two of darkness and a house full of guests I will haul out the 2K Honda and run it as a battery charger consuming around 2-3 gallons of fuel. Usually that is our only annual use although we have very occasionally had a surprise long dark period which will catch us with the need for another gallon or two.
Much of the year we are fully charged by midday and the charge controllers are kicking in. We usually do almost all our cooking and baking with electricity until we begin using our wood fired range in the late fall. We consume around 250 gallons of propane for domestic hot water and back up space heating.
This is not intended as a argument with Martin's basic and important point which is that a grid tied PV system with or without a battery backup is most desirable both from the point of view of the consumer and from the perspective of environmental impact. We are consumers who because have spent much of our lives living with limited electricity have habits of careful consumption. One of the surprises with our current system is how often there are opportunity's for additional consumption because we cannot feed into the grid when the batteries are satisfied. Nowadays because of the regressive and punitive nature of the net metering agreements offered by most of our Wisconsin utilities, I recommend the general strategy of designing homes to consume as much electricity on site as possible. This means houses that are using electricity for heating, cooling and cooking.
I would certainly not build the same house today that I started 40 years ago and I would be able to install a far less expensive and more robust electrical system then the one we happily live with.
Mark,
You wrote, "It is certainly fair to say we have paid a premium for a often limited amount of electricity especially in the early years." It sounds like we have walked down similar paths.
I acknowledge it is possible to reduce generator run time -- especially if an off-grid homeowner can afford $6,000 to $10,000 of batteries, $10,000 of PV modules, and a wind turbine. I'm not at that level of investment yet, although I've heard similar reports from off-grid homeowners who've made such investments.
Thanks for sharing your story.
Yes, many thanks to all for the first hand experiences. It's appreciated.
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