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


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)

I sell propane and propane accessories. Solar is teh devil

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.

Categories: Electric and Power


Grumpy51 · April 10, 2024 at 6:56 am

I’m a solar neophyte (have four 300-watt solar panels going through a Victron 150/70 controller and two 300-watt solar panels going through a Victron 100/30 into four 12-v 300aH batteries wired for 48v) – strictly for backup power for freezers.

Your explanations are detailed and eye-opening. Thank you for the information.

Bad Dancer · April 10, 2024 at 8:08 am

One thing that has truly impressed me with the progress of solar tech is the lifespan of PV cells and integration of smart monitoring controllers to really get every zap of power out of it you can.

Long gone are the days of strategically acquiring heavy as heck marine batteries from RV and boat lots and SWAGing your way through the red or green status LEDs to diagnoise the system based on how fast it is blinking.

The warranties are another awesome thing and at the cost of the parts a nice comfort.

We’re living in the future.

Dan D. · April 10, 2024 at 8:49 am

When the Apocalypse arrives, all the Smart Boy Preppers will be over at Newton’s arguing on a chalkboard about electron current vs. conventional current flow and whether to use field oriented control or Hall sensors to commutate motors through phase vector diagrams. While at the other end of the street, Clevon will be making babies, using old motorcycle starter motors to run his A/C and carrying maxipads in his IFAK instead of worrying about whether the seal is broken on his green Israeli bandage.

D · April 10, 2024 at 9:55 am

> For comparison purposes: 10kW (AC) system = 11.7kW (DC) system. The difference is caused by technical reasons that we won’t get into here.

Darn it. I’m interested in the technical reason. Is that due to things like inverter efficiency and loss? Because my understanding is that wattage is wattage regardless of how you convert amps and volts.

> The sizing tiers established by Florida are measured in alternating current (AC) wattage

So now my “fuck the government” side comes out. Store the power in DC and never invert to AC. Get some spiffy DC lighting, DC aircon, and various DC appliances and tell them to pound sand. πŸ˜‰ (Yeah, I know it would be a lot more expensive)

> I have a policy of not doing business with anyone who calls me without me contacting them first.

Glad to know I’m not the only one that keeps a shitlist of names, numbers, and companies that I will absolutely never do business with again.

I guess the only thing I haven’t seen you touch on is grid reliability.
We live out in the middle of nowhere. There are large pine/fir trees everywhere. There are only a handful of houses in the square mile around us….and yet somehow…other than a few brief flickers from time to time while a tree branch makes contact with a line and gets burned off…we’ve only had two big power outages in ~15 years.

One knocked us out for a few hours. The other was a totally-preventable outage caused by a tree falling and taking out a pole, transformer, crossbar, and a bunch of switches…the tree had been very obviously leaning at a near-45-degree angle for a month. I called PUD about it several times. The last time I called I said “The storm that’s arriving tomorrow? It’s definitely going to come down and damage equipment. Someone needs to deal with this.” They didn’t. We were out for 19 hours.

Reader · April 10, 2024 at 10:10 am

Even small solar & battery setups can power some essentials. There’s plenty of youtube videos on a solar power system for just emergency lighting and refrigerators that are controlled by the plugin dial timers.

this guys not making videos anymore but even at 11 years old the setup he used was good enough for his fridges, lighting, and a few other things in his house in NC.

    Divemedic · April 10, 2024 at 10:23 am

    I want more than that. See the part above about how each person’s needs are different.

      Reader · April 10, 2024 at 3:41 pm

      Yep, just sharing cuz caring.

Anonymous · April 10, 2024 at 10:43 am

Can you buy a used Powerwall from the neighbor with four? Sounds like you will be replacing the batteries every fifteen years, without a tax rebate. How does that change the price calculation? Does that require savings starting at $1.5K/year and growing at 13%/year cost of living increase? You also want to install thermal solar for hot water, because this is a large load which you don’t want to bottleneck through electricity.

Don W Curton · April 10, 2024 at 12:01 pm

Thanks for putting all that info out there. I’m more invested in a generator simply because I have natural gas available at the house, but I have no hard numbers to compare yet.

One kinda off-topic comment about your plan to refinance the mortgage. We hit a snafu when we went to refinance our mortgage here in Texas. During the refinance, I took out $10k for roof repairs. Unbeknownst to me, this caused the loan to be classified as a “home equity” loan instead of a refinance mortgage. This was 15 years ago. Under Texas law you cannot have two home equity loans at the same time (Florida may be different). So in the current year, I go to get a home equity loan and get turned down. WTF? I then find out that they classified the refinance as home equity 15 years back. So right now I’m sitting on a quarter-mil of equity I can’t touch because of a 10k roof repair 15 years ago. Be real careful on that refinance, as it may have some long term implications.

IcyReaper · April 10, 2024 at 4:03 pm

It amazes me how power companies can set rules on solar that make no sense except to make them more money.
Dam, who do they think they are,Politicians?

Comments are closed.