Designing Our System

This is the latest in our series on energy as a tool for prepping. The rest of the series is here:

• Resiliency: Backup power March 25, 2024
• Energy April 2, 2024
• Electricity April 3, 2024
• The hazards of batteries April 5, 2024
• Load Shedding April 8, 2024

YMMV

Let me repeat the following disclaimer, mostly because people keep commenting and asking me why I didn’t discuss power factor, some other brand of solar or batteries, or propane. I did research on batteries, and I don’t want to spend all of that money on propane that I will just wind up having to convert to electricity for air conditioning, anyhow. The numbers just don’t work (see the above posts as to why they don’t)

You engineer types, this is a simplified discussion that was designed to give you all of the information that I considered and discovered in my research for a backup power source without bogging you down in details that are largely irrelevant. I am trying to keep things easy to understand, so spare me the discussion about how holes move. I am also excluding things like power factor, vectors, and other things that needlessly complicate the discussion.

Also remember that each person’s situation is different. Compare my climate situation to a fictional person in Starke County, Indiana (all weather data from best places) as an example:

• While I have mild winters, hot summers, along with lots of sun and humidity, another person living in Starke county, Indiana might have cold winters, less sun and humidity, and warm summers.
• Indiana gets 34 inches of snow per year, I get none.
• Indiana has an average summer high of 83 degrees. Central Florida, 94 degrees. I see 90 days per year where the temperature rises above 90 degF, Starke County Indiana sees 9.
• Indiana has an average winter low of 16 degrees, Central Florida, 46 degrees.
• Our guy in Indiana has 129 days where the temperature goes below freezing and 6 days spent below 0 degF, I have 6 freezing days and the temp never goes below 0 degF.
• Indiana has an average summer humidity of 62 percent, winter of 20 percent. Central Florida has an average summer humidity of 73 percent and winter of 50 percent.
• Northern Indiana averages 4 peak hours of sun per day. I average 5.2.
• Where I have 232 sunny days per year, our fictional guy in Indiana has only 170. Combine that with clouds, sun angle, and other factors, and our guy in Indiana gets 30-35% less power from sunlight than I do. You can calculate your own by looking here.

For those reasons, solar makes more sense here than it does in northern Indiana. Your mileage may vary.

I don’t need to heat much in winter, but I need to do significant cooling in summer. Maybe your area is different- each of us has to do our own calculations and studies, which is why I posted so many posts about my decision. I have spent quite a bit of time looking into this, and you should, too. It’s a large investment, and not to be taken lightly.

What are We Getting & Who is Installing It?

We have decided to go with a hybrid solar system (meaning solar with batteries) and we know roughly how large of a system we need, now its time to get more details.

At this point, we will look at which system we are installing, and who will do the installing. One of the things that I noticed is that solar companies are better at selling solar than they are at anything else. They will play this sort of shell game with you- they mix in financing, tax credits, and other facts, overwhelming you with information to disguise the true cost of solar. It’s worse than buying a used car. That’s kind of what spawned this series of posts. I wanted to organize the information in my own mind, while at the same time helping others to cut through the bullshit.

In researching for this buy, I talked to a dozen different people in my area who already had solar, including three people in my neighborhood. My wife and I have a somewhat left leaning friend who bought the empty land next door to his home about a decade ago and put in a ground mounted solar array because he is worried about being green. We consulted him because, hey, a decade with solar. Yeah, he’s a lefty, but not hard core. He’s also a veteran and a nice guy. His advice was helpful.

We also looked at online customer service reviews, a ton of reference materials, and we consulted with the sales people of half a dozen solar companies. Manufacturer’s websites were also referenced. This article is a summary of what I have found out after two months of research.

The Batteries

We know that we want system rated between 9 and 10kw, but how many and what kind of batteries do we need? The 900 pound gorilla in the mix is Tesla. The Powerwall 3 just came out, and it has some impressive numbers. It stores 13.5 kwh of power, and can deliver 11kw continuously, which would drain the entire battery within slightly more than an hour. The company is claiming a brief surge capacity of up to 30kw, which is pretty outstanding. Still, that amount of power isn’t going to be enough to run the house in a grid failure without cutting to essential loads only. This means that we will likely need two of them. Batteries aren’t cheap, but we will get to that in a bit. Two batteries will mean we can deliver up to 22 kw continuously, and will have a total storage capacity of 27 kwh.

The Tesla battery has some nice features. The battery itself comes with an inverter, the gateway, and the backup relay that will isolate the system from the grid in the event of a power failure, so we won’t need to purchase any of that separately. Each Tesla Powerwall 3 can support up to 3 expansion battery packs. The expansion has the same capacity as the main one, meaning that a Powerwall 3 and and expansion pack gives you 27 KWh of storage, while two expansion packs would give you over 40 KWh of storage.

The system also has a nice app that allows you to monitor and control the system remotely. This software also watches the weather in your area and will make sure that, when inclement weather is approaching, your battery is charged to 100% to prepare for a power outage.

I have looked at other batteries, but none of them had the power specifications that were as good as the Tesla, and the ones that did come close were in the same price range or were even more expensive, so I have decided to go with the Tesla Powerwall 3.

Florida Law and Solar

Florida has laws classifying the size of a solar installation.

• Type 1 systems are solar systems that produce 10kw or less.
• Type 2 systems produce more than 10kw up to 100kw. If you have a type 2 system, you are required to carry a $1 million liability policy. We already carry this much insurance, so it doesn’t affect us, but just be aware that the requirement is there.
• Type 3 systems are those that produce more than 100kw. I don’t know what the restrictions are, and didn’t bother to look them up because 100kw would take more space than I have on my roof.

*Note: The sizing tiers established by Florida are measured in alternating current (AC) wattage, whereas solar companies measure the size of solar systems in direct current (DC) wattage. For comparison purposes: 10kW (AC) system = 11.7kW (DC) system. The difference is caused by technical reasons that we won’t get into here.

Summing Up Our Specifications

• These quotes are for a system with 24 PV panels for a total of 9.6 to 10 kw unless otherwise noted.
• 2 Tesla Powerwall 3’s for batteries are included, unless otherwise noted.
• We also priced a Powerwall expansion, but it isn’t part of the quote.

This will give us an average capacity of 35 kwh per day in the winter and 52 kwh per day in the summer, with 27 kwh of storage and the possibility of more, if we later decide to add expansion batteries. (One neighbor has four Powerwalls, and tells me that this is far too much. He said he let the salesman sucker him into spending $40,000 on batteries.)

This should enable us to power the house without input from the grid, especially if we turn off loads that aren’t essential. Things like the clothes dryer, a potential pool pump (if we get a pool) and other luxuries can be shut off if the grid is down and the PV system isn’t generating enough power. We are planning on putting the pool pump, if there should be one, on the non-backup power bus.

Fortunately, we have a pitched roof with a rather large, unshaded southern exposure and a great pitch angle, which will ensure that the panels will get the maximum amount of sunlight. There is plenty of room there for the 200 square feet of PV panels we will be installing.

Power companies in Florida won’t allow you to install a system that produces in excess of 10% more than your average annual electric consumption. The good news is that they can’t tell me what my annual consumption is, because no one knows that yet.

The batteries will be mounted to the inside wall of the garage, next to the breaker box (load center). The remainder of the electrical equipment will be installed on the outside wall of the house, next to the utility meter. The PV panels will of course be on the roof.

Tax Credits

As I have mentioned before, the IRS has a non-refundable tax credit of 30% of the cost of a solar system. This gives you sort of a rebate on next year’s taxes that subsidizes nearly a third of the cost of the system. Many companies use this to make it appear that the system is cheaper. Make sure that you get the bottom line cost before this tax credit is applied, so you know what it will cost you without confusing the issue.

In Florida, solar systems are exempt from sales taxes, and any value that the solar system adds to your home is not subject to property taxes.

None of the above tax credits are available to fuel powered generators, and was a big reason for me not going in that direction. The tax advantage gives installing solar more than a 37% pricing advantage over a standby generator.

Selecting the Installer

One of the problems that we had when we first bought the house is the number of door to door salesmen who came around, trying to sell us solar. Then there were the phone calls and attempted over the phone sales. I have a policy of not doing business with anyone who calls me without me contacting them first. I have found it to be a great way to prevent scam artists from making you into their next mark. Let’s begin with the technical specifications, then see what the costs will be.

I am not comfortable cutting holes in my roof, so this system is going to be installed by a professional. In my case, I contacted a few installers to get some rough quotes. Each quote includes two Tesla Powerwall 3 batteries unless otherwise noted:

• One quote was directly from Tesla. They subcontract out the actual work, and only use Tesla products. Their quote for a system delivering 9.7kw was right at $42,180.
• The second quote was from SunPower, another national provider. The salesman missed our first telephone conference, but called several days later to reschedule. They also subcontract out the actual installation. They do not use Tesla batteries, but use their own in house brand of battery that has similar but slightly less powerful specifications. Their quote was $52,880 for a 9.2kw system. They pushed hard for me to get a system with no batteries at all to cut costs, but that would make the system useless for power failures- the entire reason why I want this. The attempted hard sale of something that I told them I didn’t want and the high price were turnoffs.
• SunVena is a large Florida solar company. They quoted us $48,700 for an 8.8kw system.
• We got a quote from a local electrical contractor who has been doing solar for about 20 years. They came recommended by a neighbor who had solar installed by them. Their quote to install a 10.1 kw system was for $43,147.
• We tried to get a phone interview and a quote from a mid sized Central Florida solar installer. He was supposed to call at 12:30 in the afternoon. His secretary called at 1:00 and told us he was running late, and would call in about 15 minutes. The didn’t call until after 2pm. When he did call, he asked a few questions then promised to send over a quote with the promise: “I am going to make your choice an easy one.” The quote still hadn’t arrived a week later. He sure did make it easy to not choose his company, so that’s a promise kept.
• One more regional solar company was contacted. Let’s call them Bidder 6. They are not a Tesla dealer, but instead wanted to sell us another brand of battery. He tried telling us that we needed 4 of the batteries he was selling. His batteries were Enphase batteries that store 5kwh each with a peak of 3.7KW of surge. That means these batteries are roughly 1/3 as powerful as the Powerwall 3 and I can get more storage with a pair of Powerwalls than from 5 of his batteries. When I insisted on Powerwalls, we were quoted a pair of Powerwall 2’s at a cost of $14,250 each. He also said that we need a minimum of 30 to 45 PV panels because our home was going to use an average of 30KWH per day in the winter and 60 to 75 KWH per day in the summer. When I pointed out that this house was only using 23KWH per day this past winter, he replied that it had been a mild winter this year. At the end of it, his quote was three days later than promised and was for an 11.2KW system with two Powerwall 2’s, and the quote was for $59,900.

So now that we have contacted seven different installers and gotten quotes from five of them, we know that the quotes ranged from $39,000 from Tesla, all the way up to $59,900 for Bidder 6. With the 30% tax rebate factored in, the quotes look like this (from least to most expensive):

• Tesla $29,526
• Local Electrician $30,203
• SunVena $34,062
• SunPower $37,016
• Bidder 6 $41,934

Each of the installers offered a written warranty that was substantially similar:

• 25 years parts and labor that the PV panels will still produce at least 92% of their rated power.
• For the Tesla batteries: 10 years parts and labor that the batteries will store 70% of their rating
• For the other brands: 10 years or 8,000 charge/discharge cycles for parts and labor that the battery will store 80% of their rating specifications
• The big exception to the above warranty was Bidder 6. Their warranty was for 50 years parts and labor that the PV’s will still deliver 75% of their rated power.

Our experience

The Tesla guy consulted with us by TEAMS video call. He didn’t know anything about solar that was outside of Tesla’s product line. Their quote was nearly identical to the electrician, especially when you consider that the local electrician is offering a system with 400w more capacity.

SunVena sent a guy out who was the most knowledgeable of all of the solar company people that I talked to. I really liked the company. It’s too bad that his quote was $3000 more than the local electrician and $7000 more than Tesla.

The local electrician had the least polished of the presentations. The guy who came out knew about solar, he just wasn’t a salesman. However, he knew what he was talking about and had competitive prices.

SunPower was the one that frankly rubbed me the wrong way. He tried to push me into products I didn’t want. Like Tesla, the company only sold their own products an no others, and he seemed more interested in making the sale than he did in pleasing the customer. His price being $7,000 more than the electrician was the nail in the coffin.

Bidder 6 tried telling us that we needed at least 11kw and two Powerwalls, with the possibility that we would need 17kw and three Powerwalls. Now we are getting into a price point that I just don’t want to pay. His quote of $60,000 was simply way too high to be considered.

My Choice

So for the above reasons, the choice is between Tesla and the local electrician, with the electrician being ahead. I will ask them for more specific plans to see more details. This will require a more thorough engineering inspection of my house by them. Tesla is refusing to do a more in depth study unless we contract with them, so we are probably going with the electrician.

Since a standby generator would cost us in the neighborhood of $16,000, this system is slightly less than double the cost. We do get the benefit of vastly lower utility bills, though. Our bill will go from a winter $150 and an estimated $250 in the summer, all the way to the minimum $35 electric bill year round. That will save us about $2400 a year in utility bills, so the difference between this and a genny will be paid in about 5 years (counting the fuel that we won’t have to buy and the fact that long term maintenance for the genny is higher).

The timeline is tricky. We are trying to sell our old house, and will be using the proceeds to install our solar power system. The remainder of the proceeds from the sale will pay down the mortgage on the new place, then we will refinance to a 15 year mortgage, which will cut our house payment by about 70%. So we are waiting for the sale of the old house before we move forward.

We need some time to see what our hot weather electrical needs are going to be, and the delay for the sale of the old house will hopefully give us a better idea as to how much our summer bills will be.

For the time being, that means we are waiting until May or possibly even later before we are ready to sign a contract. That gives us time for engineering inspections, final proposals, and for us to get a better idea of what power we will need for summer air conditioning. Once we move forward, I will update this with any new information that we have. I will also do other updates to answer questions.