We are stuck with technology when what we really want is just stuff that works.
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Read MoreNew Projects at the Solar Shed
I wrote the material below quite a while back and it somehow fell through the cracks. I have since gone through a couple of variants of a Zero Export Grid Tie system, including a new one this past weekend…and the power company’s meter hasn’t budged since! Read this to get up to speed and there will be more on the latest changes.
The season is changing and so are the solar connections at the Solar Shed.
Grid Tie can be the cheapest way to get into solar and can even turn a profit for you in some places. In other places, the system is rigged.
A much cheaper way to do Grid Tie is a Zero Export Grid Tie (ZEGT) system, using solar power mixed with grid power to run your loads, but not to back feed into the grid. I call this “house tie solar.”
Why is this even a “thing”? Why not just grid tie, using the grid as a virtual battery? Straight grid tie with net metering is a great deal where you can get it. Daryl, in Texas, has a great deal on grid tie and his huge system actually makes him an income stream. A lot of places you can’t get it, though. A lot of places where you could get it have changed the deal. Bruce, in Pennsylvania, ran into this. He’s the one who reminded me of ZEGT.
Let’s say you live in Alabama. I think a recent article said they have $50/month tie fee and it is going up! Here in Scenic West Bogia Heights, Florida, that’s sort of the same sort of deal, but ours is higher if you can even work it out. You pay for a bunch of extra metering equipment and an electrician to install it. Your solar system has to be signed off by a certified tech. Then, on a monthly basis you have your basic $40 connection fee and a $60 solar fee. That a hundred bucks of power bill before anybody gets any power.
Turn on the juice and all the power that you make and don’t use at the time goes to the power company for less than 4 cents. At night, you get to buy your own power back for 13 cents. I am no math genius, but I think under these conditions it will cost you more to have solar power than to go without. Maybe we should run some numbers on this.
Let’s say you use 1500kwh per month. You build a grid tie power system that can supply 1500kwh per month. At 13 cents that’s $195 from the power company. Now let’s figure that the a/c and fridge and the miscellaneous loads (like the clock you can’t set on the DVD player) will use 500kwh in real time, reducing the intake from the power company to 1000kwh, which at 13 cents is $130. 1000kwh of your excess daytime power went to the grid at 4 cents per kwh. You get a credit of $40 off the $130 net grid import, so you have to pay $90 for your power. You also have to pay another $100 for the meter and solar fees. That makes your bill $190 with your grid tie connection. Without it, your bill would have been $195 plus the $40 meter fee, or $235. Ok, so you did save $45. Did I mention that West Bogia Power and Light also requires that you buy a multimillion dollar insurance policy to indemnify them should your dinky little power system damage their grid! The average squirrel can cause more damage to their system than a proper grid tie system can! Hold on, now, I have a solution or two for you.
First of all, and this costs little or nothing, change your ways. If you use more of that solar power before it leaves the house, then they don’t pay you 4 cents and charge you 13 on the power that goes out and comes back. If somebody is home during the day, do the laundry and baking then, instead of in the evening. Set the thermostat for more run time during the day instead of at night. If no one is home during the day, is someone close enough to come home and start the dryer? If nobody can make it home during the day, start a crockpot meal before you leave for work and set a water heater timer to heat during the day. Look into smart appliances that can be controlled with a phone app while you are away!
Having shifted your loads a bit, you are now burning 1000kwh of solar and 500kwh from the grid. You are also selling 500kwh to the grid. That comes to 500 x 13cents to buy, 500 x 4 cents to sell for credit or $65-20= $45. Now add in the various fees and the bill comes in at $145.
Let’s review. Your bill without solar would be $230. Your bill with the first grid tie example would be $195. Changing the routine a bit the bill with solar is $145. OK, I think we are getting somewhere. What else can we do?
The availability of ZEGT can help get new prospects into solar and can help get folks who have had the rules changed on them get back into a profitable state.
Let’s go back to our example, only now no power is backfed to the grid. We CAN make 1500kwh, but we still only use 1000kwh during daylight hours. We discard the excess capacity because we are not exporting to the grid.
As with the previous example, we are importing only 500kwh from the grid. Again, that’s $65 for power, no credit for exported power, $40 for the meter fee and NO SOLAR CONNECTION FEE. That makes the bill $105!
Let’s try that in the example before changing our ways with power consumption. I believe we were using 500kwh of solar, dropping what we buy from 1500 to 1000kwh. That’s $130 for the power you buy, plus the $40 meter fee, for a total of $170 as opposed to the $195 you were billed when the power company was “buying” your excess power!
As usual, your mileage may vary. Your power company may charge more or less, pay more or less and have different requirements and fee structures. Zero Export may or may not be for you. A lot of you have banged on the calculator and are now wondering what it is going to take to build your new ZEGT system or convert your existing GT system.
If you have an existing GT system, RTFM. That’s right, read the fine manual for your GT inverter. Many, especially those made in the last few years, have this capability built in if you add a device to monitor the power line and report back to the inverter. These go by various names, often coming in the form of a power meter or electricity meter, originally intended to just let you monitor your system. Two current transformers slip over the grid lines coming into your breaker box. They connect to the “meter”. The meter has an RS485 (or other communications standard) that connects with the GT inverter. A few changes are selected from the inverter’s menu and now the inverter knows when the solar power need to get in and out of the mix to match the consumption, when possible, but not overdo things and send power out. Hence, you can tell your power company to pull the extra meter and discontinue grid tie.
If you do not find anything on export limiting in your manual, check out a company called ELGRIS. They have an export limiter that they claim works on a lot of GTI models and may have one for yours.
Now for new solar users, hold on. There are reputedly some inexpensive modules that will do the trick and installation is pretty easy. I say reputedly because I have not personally tried it, but I have heard good things. I have ordered two units and will quickly get them installed on my minigrid for testing the ZE claims. If that goes well, then I’ll go live with them and report results, like whether or not the power company busts me for backfeeding. Tom got a visit from the power company within 2 hours of inadvertently backfeeding his system, so going up against West Bogia Power and Light with these new gizmos is a really good test.
I’ll let you know.
–Neal
Why Me?
Kris Kristofferson had a big hit with a song on that theme. Instead of moaning about why things had gone so wrong, though, he was wondering why good things had happened when he felt he didn’t deserve them.
Well, things can go wrong in your solar power system, just like anything else, and you’ll have to get off your wallet to fix them. You can ask, “Why me?”, but if you are just feeling sorry for yourself it’ll likely happen again. If you ask “Why me?” constructively, that is to say, analyze what you might have done differently, you might end up with a better and stronger system that won’t have such a failure in the future.
Here at the Solar Shed, I have all kinds of experiments running. Many are temporary, but sometimes stick around longer than expected. If I get sloppy on these temporary rigs, then it can get expensive. Also, different circumstances seem to offer different “learning experiences”.
Example 1–Do you know what the schematic symbol is for an antenna? Visualize an upside down wire coat hanger and you have a pretty good idea. If you have 3 solar modules in series, you can twist all the wires together and have the pair for the downline together or you can have them take the shortest path, with ends up with a more or less triangular circuit…just like the antenna symbol. Now, a loop antenna is directional, so if lightning hits the tree over yonder, the induced current from the blast may be out of phase and not bother your system a bit. OR it may be 90 degrees around and channel the hit right into your system, which can get expensive. Trust me, I know this to be true. Keep your wiring tight and not looped.
Example 2–If you do not have a surge arrestor on your system, you should not complain about a surge getting in and causing havoc. In the spring time, we have some really nasty lightning storms around here. I mean, go hide under-the-bed-with-the-cat-bad storms. In a case of Example One and Example Two combined, you may discover interesting things. For one, a charge controller might NOT be injured by lightning, but because it operates slowly it can pass it along to your inverter. The inverter monitors its output and adjusts according to the input with which it has to work, but this adjustment is not lightning fast, so you can get some really interesting effects. One brand of inverter I had online would blow its display board. It was the weakest link and it took the hit, saving everything else. It would run just fine without the board, but I had spares. After a couple of times of this, I was out of spares and decided to run without display. I had other meters. I did, however, lash up an output surge arrestor. Good thing. The next storm did not kill the inverter, but it wiped out the feedback loop, so it got the urge to keep making lots of voltage…lots more than is considered socially acceptable. Fortunately, I had put in that output surge arrestor and only it went up in smoke. Otherwise, everything in the house on that circuit would have been destroyed. The saddest part of the story is that my new 48v system, not yet online, lost its big 12kw inverter. Have you priced a 12kw inverter? They cost a lot more than surge arrestors! I think the system packages that Sun Electronics sells pretty much have arrestors in the kit, but ask. If building a system a la carte, install surge arrestors!
Example 3–Nothing bad happened, here, because I was prepared. Lots of gear has fans in it. All of my charge controllers have them and the Sun King 5548 inverter that I built in the shell of my deceased 12kw inverter recently had one of its fans start getting noisy. There is a manual fan in the top of the case that I use a lot in hot weather and another fan operated by a thermostat on the transformer. That one never runs as I am running 5500 watts on a 12,000 watt transformer. Right down on the driver board, there is a small fan that runs based on the heatsink temperature. This one is pretty important and it would rumble and howl when it started up. In this inverter’s design, heat won’t cause it to blow up, but it will shut down until it is comfy again. Having the lights and a/c blinking on and off on a warm day is really annoying. Folks, when your fans start talking you need to listen. I have a drawer full of fans for just such occasions. I bought two extra when I built the inverter and I have several more dissected from old PC power supplies by an 11 year old who likes to take things apart. Never throw away working fans! If you buy replacement fans, TRY to get ball bearing fans. They cost more than fans with sleeve bushings, but they last WAY longer. The specs, like voltage, current and airflow (CFM) are usually printed on the hub of the old fan. Listen to your fans. They mean it!
Example 4— Pay attention to the meters. I recently pulled a set of 2 year old batteries from the system. Why me? I have batteries 5 years old that are just fine! Interestingly, it wasn’t just one battery with a bad cell. I was hoping to use some of that set in other 12 and 24v systems around the farm, but No-o-o-o-o, they were all bad. Curious. Well, it seems I had two charge controllers that had a bad firmware revision and may have had some damage from all those lightning episodes. Since they run less than half the power for the whole system and otherwise seem well-behaved, I ignored the high-ish afternoon voltages, thinking they were supposed to go that high as part of their multistage charging act. Nope, they were cooking the batteries. Pay attention to the meters. They are there to tell you stuff!
Example 5–Unless you have sealed batteries or some of those fancy Lithium packs, then there’s a good chance you will need to add water to your batteries from time to time. How often depends on how hard and how deep they are cycled. If you pretty much use up the battery at night and have enough solar to charge it hard, you will probably go through a good bit of water. Once a month is probably good for most folks, but that previously mentioned set that died young was going through gallons every two weeks. Keep the water above the plates and use only distilled water. It is only a buck at the grocery store or WalMart.
Example 6–Keep your terminals tight and clean. Terminals just get loose and need to be tightened. Otherwise, they can run hot and waste power or even burn off the lugs of your battery or inverter. Just today, I opened the cover of a charge controller to get to the temperature sensor wire and while I was in there I decided to check the terminals. Two were not loose enough to cause harm, yet, but needed to be snugged up, just the same. On your batteries, you can add the threat of acid corrosion. Don’t let that green stuff build up. Clean it up and coat with grease for protection.
Example 7–Pay attention to the heat. I haven’t had any problem from this, but it got uncomfortable in the Solar Shed’s control room/man cave last summer. There was no ceiling, then, and the backside of a solar panel is hot. The IR thermometer showed 140-150 degrees and the room was routinely over 110, even with the door left open. This had its own issues, like random animals showing up on the couch. The a/c I had didn’t even stand a chance. There is now a ceiling and insulation, so much of that issue is handled. I will be adding a vent fan and, budget permitting, a mini-split heat pump. Mostly the heat pump will be for me. A check of the spec sheets on all the gear indicated we were well under the too-hot mark. If you don’t have temp specs, you can check the equipment itself. Lick a finger and touch it to a transistor. If it doesn’t sizzle, you are good. If it sizzles, you are close to the limit. If you don’t get back all of the finger, then it is too hot and you need to cool things down.
–Neal
One Bad Apple…or Battery
You know the old saying about one bad apple causing the whole basket full of them to go bad. The same thing applies to batteries. I am there, now, and so is Mark. Like me, Mark seems intrigued by the Simpliphi lithium batteries, but is also interested in getting a little more life out of what he has. Here’s his note.
Ok, since my 8 Rolls L 16 batteries are 8+ years old, all but one (one cell is 20) are reading good PH, would it be better to get 1 battery new or replace with a Simpliphi? How much do they cost and how many would I need for a 24vDC, 3KW 220 volt a/c system used as a backup on house? It’s the old array and battery bank, we have since added a separate grid intertie array but like both.
We will first consider stretching the life of what you have. I am all for that, but I would NOT buy a new one to mix in with the 8 year olds. Have you given them a good, bubbling equalizing charge? Sometimes that will bring them back.
It may be that you can find a good used one at an industrial battery dealer. Stores like WalMart and Target use L16s in the floor scrubbers and trade them out. Maybe you could pick up a used one, and one that is a better match, for a hundred bucks or so.
Another option would be reconditioning. Here in Pensacola we have an outfit called Battery Guyz that will sell a reconditioned golf car battery for $60 with a one year warranty. Reconditioning includes desulfating, washing them out and refilling with fresh acid. Maybe an outfit like that could refresh your L16.
Now, as far as replacing one of your L16s with a Simpliphi…NO! The L16 is 6v. The Simpliphi is 24 or 48v, depending on the model. You can replace your entire collection of L16s with Simpliphi. Could you keep the one good bank of L16s and run parallel with Simpliphi? I don’t know the battery well enough to answer that question. I have the same question myself as I have two 48v EVs running in parallel to my house banks. It is a possibility I would look into by contacting the company. From what I read about the Battery Mangement System (BMS) I think it is a possibility, but you would probably have to separate the L16s offline when you equalized.
Let’s assume the worst, that we’ll have to swap out them all and start with his L16s’ specs. 8 of them on a 24v system is two strings. Depending on which version he bought, they are good for 390 or 445 amp hours. Let’s just round off to 400 since I hate math. 400ah x 24v x 2sets=19,200. Call it 20kw. Now, you can only safely draw down 10kw, so to replace the entire set of L16s with the Simpliphi 3.8kw units, you’ll need 10/3.8 or 3 of them. Because of all the rounding, they may give a little more drawdown than the 16 Rolls. One Simpliphi, I think, weighs less than an L16, and 3 of them will take up a whole lot less space.
Here’s the kicker. The Simpliphi is rated for 10,000 cycles. That’s more than any other lithium I have seen. 10,000 cycles is 27 years. If you are my age, then that is a “forever” battery. And no maintenance.
You’d have to get with Roberto or Tony for some hard prices, but I would guesstimate that 8 shiny new Rolls L16’s, a premium brand, would set you back around $3000, especially if you throw in postage on those heavy beasts. I think the retail on the Simpliphi is around $3000 each. So you end up paying maybe 3 times as much for 3 batteries as the pile of L16s. Yikes! BUT, now you have more capacity, less maintenance, and may never have to change a battery again. Oh, and bet that if an L16 is $350 today, it will be more 8 years from now!
It’s a bunch of money, I know, but if I am running the numbers right, that sure sounds like a bargain to me. Call Sun Electronics to get up-to-date numbers and an actual quote.
–Neal
Note that earlier I ran the numbers for 16 batteries instead of 8. That gave a completely whacked comparison, but the conclusion remains the same.
Solar Rescue update
Stan called and he was happy.
His old 12v system, pictured above, is really getting tired. It consists of nearly 50 mismatched modules and two windmills in parallel on a single overworked charge controller! His new 24v system is running, but only half-installed and there have been issues.
After our little troubleshooting session the other day, Stan-the-Hermit left the cabin on the creek for a few nights on the beach. He’d returned to the creek to find his batteries were full for a change. Of course, to zing me, he started out like there was some kind of problem.
Best news of all, for the first time ever, he ran his well pump and got all of his tanks charged up so he could bathe. Normally he has to fire up the generator to run the well pump, but it started and the charge held until all four of his tanks were full and the pump shut off. Given that his inverter is of the modified square wave variety, that’s quite a feat, as motors tend to prefer sine wave inverters.
To review what happened, Stan THOUGHT he had 5 of his 10 300+ watt modules connected in parallel to his 60 amp charge controller. Owing to a bad MC4 connector, 3 of them were actually NOT connected. Just as well, because all 5 of them would have exceeded the capacity of the charge controller. We replaced the connector and reworked the arrangement to two series pairs of panels, which reduced the amperage (and loss) on the downlines and gave the controller a little more voltage to work with in the morning and afternoon.
He swears he will finish wiring the rest of the modules and return my big roll of wire. I hope he remembers that if his 60 amp charge controller isn’t big enough for 5 modules, then his new 40 amp controller won’t handle the remaining 6 modules. I’ll be expecting a call next time the sun comes out.
–Neal
Will Has a Question, Part 3 1/2
Here is an interesting battery for Will.
Yes, it HAS been a while since the last post. This time of year just seems to keep me busy.
Last update on Will’s system we essentially concluded he is going to need a huge battery. Batteries should not be a system afterthought. They are probably the most important and expensive part of the system. Do it right and you can minimize having to do it again, unless you can find a “forever” battery.
I know Sun Electronics has several kinds of batteries, because I have been there and seen them. And bought them. The thing is John has all kinds of stuff that never gets shown on the web site until they have a closeout sale. I bet John doesn’t even know what lurks in the back corners. Sometimes it doesn’t hurt to just call them and tell them your situation and maybe they’ll surprise you.
Well, in a conversation with a fellow who got a quote from Tony for a pretty substantial battery, I learned about one that is real interesting. Understand, MY interest because right now I have one bank that is well on its way to ruin and others that are pushing up to 6 years old. I need batteries myself. Golf car batteries are generally considered beginner batteries and the better stuff can cost a lot more. Better can last a lot longer, too, making the expensive stuff cheaper. We’re talking about quality, here.
Well, here’s this lithium battery, the Simpliphi 3.8. It comes in 24 or 48v configuration, 3.8kwh. It is the good kind of lithium, that is they don’t burst into flames. It is much lighter and much smaller than conventional batteries, so if you need a really big (capacity) battery, you don’t have to build a new wing on the house to hold the battery. Apparently the built in battery manager (BMS) let’s you use it like any other battery and, in effect, go to 100% discharge of rated power. The BMS holds the necessary reserve to keep from harming the battery.
So, with a lead acid battery you strive to use less that 50% of capacity to maintain better battery life and the Simpliphi lets you use 100%. That means you have an even smaller pile of batteries in the power room. Throw in a lot more useful cycles (around 10,000) and this battery starts to look economical if you take the long view.
Unit size is 13.5″x14″x8″ and it weighs about 78 lbs. 3 of these weigh about the same as 3 1/2 Trojan T105s and have the usable power equivalent of around 16 of the Trojans! Wow.
It seems there are wall brackets available to fit these batteries, too. Compact, long life, neat installation, no hydrogen or acid fumes and long term economy. What’s not to like?
–Neal
In the News
Just a few notes on solar in the news. Click in the parentheses for the links, since I can’t seem to make them show up in some browsers.
A really biased (headline) blames California power outages on climate change. The actual cause of PG&E outages is PG&E pulling the plug when it gets breezy! Proper powerline maintenance, line stabilizers and right-of-way maintenance to reduce fuel would go a long way to prevent fires from powerline sources. Better forest management wouldn’t hurt, either. Of course, they famously turned off the power to millions and there were fires, anyway. Today it was reported that they turned the power back on and a line fell from one of their newer towers (47 years old), starting another fire. The positive thing coming out is people and businesses are scrambling to find solar and battery solutions to keep their power on and their businesses open. They could learn a lot from John’s customers in Haiti.
Next up is recycling. Solar power has changed so fast that facilities are changing out the panels they installed a few years ago, going for the higher output of today’s panels in the footprint of the old ones. That leaves truckloads of perfectly good panels looking for a new home. That’s just one way John brings cheap panels to Sun Electronics customers. That’s why you can buy a 70 watt panel, single piece, for $12, or as low as $7 in quantity. Or a 300-ish watt panel for a hundred. Another source is insurance claims. It seems that if a half dozen panels get popped in a hailstorm, they’ll go ahead and replace the other hundred thousand, just so they’ll all match. More bargains. You and I putting those surplus panels to work is the best form of recycling. Then there are those that are well and truly smashed. As John has pointed out in his blog, there’s no good way of recycling them, yet. The growing pile is prompting lots of new research on ( recycling and reclaiming. ) Of course, there are new surplus modules, too. Companies go bankrupt or get into some sort of bind and there’s another container load of them.
Finally, something fun. Are you wanting to try your hand at solar power? Is your kid looking for a science fair project. Check out the American Solar Energy Society’s ( Tiny Watts) program. Program members build their tiny watt phone chargers, battery chargers, portable lights and all sorts of things. I guess the solar toys John used to have would qualify. I put a solar powered spider on the table in Mom’s sun porch and it would drive her cat nuts! Inspired by Solar George, down in the Keys, I found a couple of 6″ panels from a yard light and will turn them into USB chargers. I figure you can use them directly to charge a phone, but I will go one better and let it charge one of those USB battery boxes. The battery box, using 18650 cells reclaimed from my pile of old laptops, can then charge two phones any time of the day or night. What kind of Tiny Watt project can you make? Check the link, above, for ideas.
–Neal
Don’t Do This!
This morning, going through the email editions of American Solar Energy Society’s Solar@Work and PV Magazine, I came across an article on things found wrong during inspections of photovoltaic power systems, both at home and commercial installations. You might want to take a look at the article and then take a look at your own system! https://pv-magazine-usa.com/2019/09/19/solar-power-installation-techniques-dont-do-this-w-pictures/
–Neal
A Hot Time at WalMart
Don’t Try This at Home
Did you hear about the solar panel fires on the roofs at various WalMarts? Don’t let it happen to you!
Little bits and pieces of this story have been coming out in the solar trade press for a few weeks, now. What I have gathered from this is that the rooftop solar power systems at 7 WalMarts have caught fire. The roofs were steel and the stores were not extensively damaged, but the WalMart folks are miffed enough to sue Tesla over the affair. Elon Musk’s Tesla did not install the systems, but they bought out Solar City, so it is a mess they inherited. Since Solar City was started by some cousins of Musk, you can wonder if the next family reunion might be a little tense.
So what does this have to do with you and YOUR solar power system? Maybe nothing and I bring it up so that we can make sure. It is looking like the problem started with connectors. Most of the panels I have came with MC3 or MC4 connectors and I have worked with Tyco connectors. MC3 and MC4 won’t fit together. Just a glance and you know that. MC4 and Tyco connectors look just alike, but won’t fit together. That’s good because the lookalike parts have just the opposite polarity. You will have to use adapters to mate these up.
The WalMart problem seems to involve mixing MC4 and Amphenol H4 connectors. They look alike and they fit. Amphenol makes no claim that an H4 is an MC4-compatible connector and vice-versa. The problem is, the Solar City installers used them interchangeably and the fit is a little sloppy. Word is, Solar City knew of the problem and had begun a program of swapping out for truly matching connectors. They just didn’t get to some in time and now the lawyers are swarming.
Something that can exacerbate the problem is not plugging them in tight, even when everybody is using the same connector. Sometimes MC4s are really quite snug, getting that rubber seal seated. When locked they can be a real pain to get unlocked, if you are experimenting and it would be really easy to forget and leave a connection half done. Aside from a loose fit, that could be an invitation to water and corrosion.
In a low voltage system you might never have an issue with loose or mismatched connectors, but in grid tie, you can get into many hundreds of volts and a fair number of amps, resulting in conditions that will start and sustain an arc long enough to melt and then ignite connectors, which in turn can melt and ignite something else. Like a roof.
If your solar was installed by Solar City, have they come by to check
and update your system? Maybe YOU should. Of course, it is a good
idea to periodically check your system because STUFF HAPPENS, regardless
of who installed it. Are all the connectors snug and not charred or
melted? Does the insulation look good? Any brown patches or cracks on
the modules? Battery cables tight? You know what it is SUPPOSED to
look like, so just look for anything that doesn’t look right.
Safety first!–Neal
John’s Home Office Solar Backup Power System
Condo Solar
As promised, I am passing along John’s description of the emergency backup system he put in his condo, years ago. Battery backup, with solar and a generator. The power does not usually stay off very long in big cities, but it doesn’t have to go off at all!
When I started Sun Electronics 35 years ago, I used my home office, it had been my Kyocera America East Coast and Latin America office. I set up this new office for Sun Electronics after working for them for 8 years.
I installed about 5 ARCO modules on my balcony railing , they were flat so I could use them as a bar for parties and just hanging out watching a nice view of the pool deck, Biscayne Bay and the Ocean. They were the perfect width and length 4 ft, by 1 foot. They were just for the office, then I added, a separate circuit breaker sub panel and added a Trace DR2424 inverter charger with an automatic transfer switch so I could have a hybrid system using a portable silent Honda portable gas generator. I could plug that back into grid to use for black outs or, by disconnecting the utility, and keep running the condo, ( the most important electric circuits: 2 refrigerator freezers (25 years old) sockets in kitchen, bedrooms and living room, minus the big loads 220 VAC appliances like stove, electric water heater and air conditioner. It was a great little hybrid system. We only integrated the Generator because Hurricane Wilma came along and put Miami back into the dark ages for 3 days. The system was so efficient and quiet that no one could see the solar panels and when the hurricane showed up we took them down and just used the backup power system with the Honda generator inverter, and 4 6V, 220 amp hr batteries wired in series (equaling 24 volts).
We went three days on that system and didn’t even use half the gasoline in the little lightweight portable, practically silent, generator because most of the time we didn’t need it after the batteries were charged and they took over we just had to disconnect the extension cord running to the generator out on the balcony that fed the house and the 70 amp battery charger in the inverter/charger.
It reminded me of the pelicans that flew by my window everyday up on the 14th floor Venetian Condominium. They’d flap their wings a couple of times (the generator) and then glide half a mile or more (the inverter output off the batteries, no noise, not even the Honda that I don’t think anyone ever noticed. Its illegal to bring gasloline into a high rise for running a generator on your balcony so we brought it up full in a cardboard box just before Hurricane hit, It was amazing to see all of Miami dark for three nights. If it had lasted more than one tank of gas I would have just reinstalled the panels on the balcony railing and lighten the load by at least half, goodby refrigerators, 6, 35 watt modules weren’t capable for that, but everything else was ok including microwave and fans a small 10 cu. Ft. refrigerator (75 watts) could have been added but just never did that.