How to become energy self-sufficient with enough photovoltaic panels and batteries
to last through extended cloudy weather.
Like almost all of us, I am totally dependent on the national electric grid, which is interconnected and controlled by 55,000 substations across the U.S. I was shocked to learn that this grid system is deeply vulnerable to terrorist attacks. It seems that disabling just 10 of them, by cyber or physical attacks, would cause the entire national grid to crash, like dominoes. And we are told that this is already being attempted, and that the danger is increasing as technology is advancing, and also, that there is no way to prevent it.
Everything would stop. No more grid electricity of course, and within just a few days also no more gasoline, heating fuel, food, meds - no more deliveries of anything anywhere - no more propane for the backup generator to pump the groundwater into the town water towers. We can all imagine it, and we know it would last for a very long time.
The only way we could survive such a total breakdown of everything in our society is to be prepared for it. I plan to prepare by becoming both energy self-sufficient and food secure. And, of course, my security will totally depend on how many in my own community will also be prepared.
If too few prepare, then most of us will suffer, because there won't be enough to go around.
So, I want to stop using grid electricity and fossil fuels - but I don't want to give up my car, comfort or conveniences. Instead, I want to power everything with solar energy by getting enough PV panels and batteries to keep enough of it running even through prolonged cloudy weather.
In this post, I will show how I plan to become 100% solar energy self-sufficient. Then, in a follow-up post, I will also show what I plan to do to become food secure, by adding gardens, greenhouse, critter-proof chicken coop, and longterm storage for beans, grains and seeds, and for root vegetables, squashes and herbs. I am calculating estimates of how much it will cost and how much it will save, thus indicating the estimated annual return-on-investment, ROI.
This is one of the PV arbors I will set up to hold the photovoltaic panels: 16 PV panels, each one @400 watts, for a total of 6400 wp - that's a 6.4 kW array.
Each panel will produce 400 watts/hour, and, with 5 hours of sunshine it will produce 2000 watts: 2 kW per day. With 100% sunny days, it would produce 730,000 watts, or 730 kWh annually.
However, my location, the island of Martha's Vineyard off the coast of Massachusetts, has roughly 50% cloud cover, plus my site has 18% shade factor (trees). Thus, each of my panels will produce 1.6 kWh/day - thus, 16 panels will produce 25.6 kWh/day for roughly 182 days/year = 4659 kWh annually from just one PV arbor.
I plan to install a total of 48 PV panels, which will produce 77 kWh on a sunny day x 182 sunny days = 14,000 kWh annually. This is more than enough to power everything, including 2 all-electric Nissan LEAF cars.
By doing this, the marvellous fringe benefit is that it will also greatly reduce my CO2 foot print, from roughly 30 tons annually down to near zero - and this is of course exactly what we must do in order to have a chance to reduce the worst of the climate catastrophes that they say are coming if we just continue burning fossil fuels for almost everything in our lives.
Of course, this would also greatly increase our security - because our fate would no longer be dependent on people, infrastructure and resources from far away, constantly threatened by wars, greed, corruption, embargoes, sanctions, sabotage.
Instead, our fate would depend on how well we do with the local resources we have available, and how well most of our community has prepared, and can get up and do what needs to be done. If only a few of us prepare for this, then most of us will die. If most of us prepare, most of us will be able to live very well indeed.
I will also show something that may surprise some of you - it appears that doing this 100% switch to solar is also an excellent investment, yielding a highly respectable annual ROI, guaranteed to increase as the cost of grid electricty and heating fuel keep rising.
So how much will my solar conversion cost?
In normal mode, my house may need avrg. 31 kWh a day x 365 days a year = 11,315 kWh/year - say, 11,400 kWh/year at 300 kWh/year per panel, which will require 38 PV panels.
Plus:
2 Nissan Leaf cars (2013 and 2014), driving average 45 miles/day total x 200 days/year =
= 9000 miles/year @ 3 miles/kWh = 3000 kWh/year
3000 kWh a year @ 300 kWh/year per panel requires 10 PV panels.
Thus, my house + 2 Leaf cars will consume 14,400 kWh a year, which will require 48 PV panels. A 400-watt PV panel is 20 sq.ft. Thus, it produces 15 kWh per sq.ft. per year.
It includes 24 monocrystalline PV panels @ 400-watt + 30 kWh battery pack + inverter + all wires + connectors.
Thus, I need 2 of these kits = 48 PV panels + 60 kWh battery storage capacity.
2 kits @ $19,000 = $38,000
Plus, I will need an additional 20 kWh battery capacity: $6000, for a total of 80 kWh battery storage capacity.
48 panels will produce 14,400 kWh a year, ranging from 0 kWh/day to 77 kWh/day.
Thus, total battery storage capacity is 80 kWh total in the new batteries + a total of 40 kWh in the 2 Leaf car batteries (10 years old and still at 90+% capacity!). Total battery storage capacity: 120 kWh, enough to provide 17 kWh per day over a period of 7 cloudy days. This is enough to run my house in mini-mode of 10 kWh/day in a week of no sunshine = 70 kWh
- and still have 50 kWh left, enough to drive 150 miles during that 100% cloudy week.
The 2 kits + 4 batteries will cost $44,000 + perhaps another $26,000 for installation, for a total of $70,000.
The bottom line:
Today, in my location, electricity costs $0.51/kWh. 14,400 kWh of grid = $7344 per year.
Thus, when I no longer need to buy it from the electric company, I will save $7344 the first year.
Also, with enough minisplit heat pumps and solar heating, I will no longer need propane for heating, and thus I will save an additional $5000/year.
And, I will save at least $4000/year by not having to pay for gasoline, oil, maintenance and repairs for 2 ICE (Internal Combustion Engine) cars.
Thus, my total gross annual savings may amount to $16,344.
Subtract the cost of annual maintenance - $1000? Net savings: $15,344/year.
Thus,
if I invest $70,000, and save $15,344/year, my return on investment, ROI will be 22%!
In a few years, the market value of 14,400 kWh may then have gone up from $0.51/kWh up to $0.65/kWh = $9360/year. And propane would likely be up to $6000/year. And the annual cost of gasoline and upkeep for an ICE car may be up to $6000/year.
Thus, I may be saving 9360 + 6000 + 6000 = a total gross annual saving of $21,360/year.
- Thus, within a few years, my annual ROI may have risen to 30.5%!
And if I instead borrow the $70,000 @ 6% over 15 years, it would cost $7080 a year.
Gross savings: $15,344/year Cost of loan: $7080/year Net savings: $8264/year.
Thus, borrowing $70,000 today will save $8264/year, yielding an annual ROI of more than 14.6%!
In a few years, the loan would still cost $7080/year, but the market value of 14,400 kWh may then have gone up from $0.51/kWh up to $0.65/kWh = $9360/year. And propane would likely be up to $6000/year. And the annual cost of gasoline and upkeep for an ICE car may be up to $6000/year.
Thus, I'll be saving 9360 + 6000 + 6000 = a total gross annual saving of $21,360/year.
Subtract the cost of the loan: $7080/year, and that leaves net savings of $14,280.
- Thus, within a few years, the annual ROI may have risen to 20.3%!
The PV panels are guaranteed for 25 years, but the batteries may need to be replaced after 10-12 years.
Current cost of 80 kWh new batteries: $26,000 + installation, say, total $30,000.
This will not break me, because, after 10 years, my accumulated savings may have amounted to more than $150,000.
Please note that all these numbers are before any Federal or State tax deductions, rebates or subsidies.
And, as always, if you disagree with my calculations, I invite you to make a comment.
Calculations are tricky, because both costs and effectivity are constantly changing - for PV panels, batteries, inverters, wires, and cost of labor. Numbers can be controversial and therefore risky to publish.
My brother, a lawyer and inventor, advised me not to include all these calculation, because they can so easily be shot down because they are so variable. And also because they cause brain fog, and therefore cause people to stop reading.
But my feeling is that, without numbers and calculations, we have no idea what the reality is, and thus we have all these negative opinions flying around - solar is too expensive - solar is too ineffective. No it is not, and I have the numbers to prove it.
I am convinced that people need to understand the numbers in order to be able to compare the pros and cons of various options - and therefore I will keep including them.