a solar home with the words affordable netzero case study written across it

I was at my Dad’s 70th birthday party, and I was meeting some of the invited guests and having a good time.

One of their longtime friends and neighbors was there, Rayanne, and we hadn’t met yet. She asked what I did and I told her that I was in the middle of doing a netzero home renovation.

She got pretty intrigued, and mentioned that she had been an environmental scientist her whole career and that she’d always been wanting to do that. She then asked how much it cost for my services to help do her own home.

I paused and said that I was doing my first one, and that it was basically an experiment. No one had ever asked me that before.

So after the party, I offered to stop by her house to do a quick walkthrough audit. Due to it being my literal first one helping someone else, I just offered to offer my knowledge on the project for free.

Two months later, Rayanne was completely netzero with the efficiency and solar projects we did. All for much less than you’d think.

That’s what this case study is about, so I’ll share the procedure and how we did it.

This was a couple years ago by now, and we here at the company have done more projects since and learned a lot in the process.

If you’re looking to do a similar sustainable project, go netzero, need help reviewing solar/efficiency proposals, or have any questions on sustainable home investments and similar, feel free to read more about us and reach out on our Services page.

The Plan To Go Netzero

Rayanne had mentioned that no one had ever really clearly been able to put all the pieces together, or otherwise clearly describe how to actually be environmental and save money affordably.

With these projects, I described, I really try to approach it holistically, looking at the homeowner’s goals first, and then making a plan based on all preferences.

It’s not just about doing a huge, expensive insulation, window, or solar project. It’s about a decision tree that we generally follow, keeping the payback low and ROI as high as possible while achieving all the goals. This is often opposite of a company wanting to sell you the highest ticket item. That’s not everyone, but it’s human nature and the way our system works.

Little did I know at the time, and before doing the BPI Energy Auditor training myself, they officially do energy audits and troubleshooting with a “house as a system” approach. And that’s exactly what we did here.

Initial Visit and House Details

The home itself is a 2,288 sq ft three bed, three bath wood-frame home built in 1986 in Fort Myers, Florida. We are not sharing the exact address due to the owner’s privacy wishes, but here are some pictures before we got started:

Goals For the Project

Rayanne had recently retired, and many of the goals were environmental but also related to not going crazy on the budget. This meant:

  • Keeping the project costs low.
  • Foregoing ones that didn’t make sense.
  • Accounting for ongoing maintenance.
  • Accounting for future systems replacements, such as HVAC, water heaters, or the roof.
  • Evening out the monthly expenses to match the fixed-income from retirement sources.
  • And, of course, being as completely green as we could along the way.

Pros and Cons of the House – Starting Point

Houses always have pros and cons as a starting point when embarking on these projects. And every house is different. Mixed with the goals of the homeowner or investor at that.

And that’s what makes it so challenging, yet fun at the same time.

Pros of the House:

  • Fairly new main-house HVAC system.
  • A light-colored metal roof that will last for decades, that will reflect a ton of heat vs. a regular darker shingle roof.
  • A great roof angle for south-eastern facing solar.
  • Lots of roofspace high up, out of the way of tree shading if we needed it.
  • A willing and open-minded homeowner, excited to do the project.
  • Low monthly energy use relative to similarly sized homes in the area – this is due to conservative use of systems, being energy-conscious to start, and keeping the average temperatures in the 80s (huge in Florida for saving on HVAC).

Challenges of the House:

  • Many rooflines and different angles – can lead to lots of leaky areas or harder-to-work-with areas.
  • Pretty big for a three bedroom.
  • The kitchen clearly had no insulation in the ceiling/attic area above it, you could feel how hot it was with your hand.
  • Fairly leaky starting point with the blower door test.
  • A separately attached enclosed back patio, which leads to:
  • A separate apartment suite with its own HVAC system.
  • Old water heater – needed replacing and located in a kitchen closet.

Blower Door and Duct Leakage Testing

A good starting point with these projects is to usually do a blower door test, and a duct leakage test if the homeowner wants to test that.

Rayanne was pretty excited about the whole process, so we decided to do all of it. She had some questions and complaints about some rooms getting too hot or too cold, or commenting that the bill was often seemingly too high.

This was a good way to get some numbers to see what our starting point was.

We had to do the whole house first, and then the separate apartment unit second. It was a bit tricky, because the two units had shared ceiling and walls, but had separate HVAC and some other things. This is why you have to test the two separately, or often together with two blower door tests in some cases.

Since I wasn’t a certified auditor yet, and was more focused on the real estate investment/renovation theme of my own home at the time, I enlisted my friends and local blower door test company Florida Blower Door, owned by the Faheys.

They have been in the industry for 40+ years and really helped with my first and second netzero renovation projects.

The Netzero Gameplan

As suspected, the house and ductwork were very leaky in areas. There was a lot of missing insulation in spots (as seen visually and also with the infrared camera) as well.

We all talked after the testing, and came up with a plan to seal all the main air leaks in the house that we could find. This includes this like:

  • Small gaps and cracks behind cabinets, faucets, etc.
  • Sealing the top plates.
  • Sealing other open areas in the attic.
  • Checking and redoing some of the caulking around windows.
  • Making sure all doors sealed tight, fixing gaskets if needed.
  • Installing insulation outlet gaskets to help close up the holes in the wall behind electric outlets.
  • Reinstalling loose insulation, adding insulation to areas where it was missing.
  • Many more smaller projects.

If you want to see more practical air sealing tips for any home, check out this article as well.

Calculations Behind the Scenes

With the blower door company tackling the project listed above to pretty much air seal and insulate what made sense at a starting point, Rayanne and I were tackling the number on bigger items.

First, we start off by looking at the monthly and yearly electrical usage, along with noting what systems were installed in the house and when:

a spreadsheet showing yearly energy use and a list of mechanical and appliance systems installed in a house

As mentioned above, in this size home in Florida, the electric bill is not bad at all as a starting point. Most homes of this size can sometimes use double this amount if not careful.

We can also look up the energy usage on each of the mechanical items and appliances. This gets us to rough baseline energy figures, and to see if they are all working properly and efficiently.

We went through each item to see what might make sense to swap out for a more efficient unit, including all the appliances.

For this project, we decided to keep all the existing items in place. None of the appliances were really going to make huge dent or have a good payback to swap them out vs. adding more solar panels, as described below.

Example Calculation Email:

I wanted to include a copy-paste from our email thread, just as an example of how I combine real estate investing, finance, energy savings calculations, and more to determine what’s best to meet the goals desired. This was us talking about going with a regular hot water heater vs. a tankless or heat pump water heater.

What we love to do also is compare what adding just a few more solar panels would do vs spending more on a different kind of hot water heater vs. a regular/conventional one. You can see these calculations and the analysis below:

On Fri, Apr 23 at 3:58 PM Erin Shine wrote:

Hey Rayanne,

I also ran a calculation that takes into consideration not doing the hot water heater (using a cheaper conventional replacement instead), and seeing how much more solar you would need. It was fun to see because I had not done this comparison yet myself either.

Assuming $300 per year savings (using Energy Guide labels) at $.115/kWh from LCEC, that’s about 2,600 kWh per year in energy ($300/.115 = 2,609 kWh). If you keep your existing hot water heater (or do a new one but same technology), then 

Per the attached screenshots and using PV Watts (solar production calculation for your exact address), and calculating with the panels with 20 degree tilt and about 120 degrees azimuth southeast (estimate) – it shows the extra solar needed is about 2.15KW. I also applied a 20% shading factor with that tall tree as a guess. 

So 2150 watts / 380 watt panels = 6 panels (rounded up). You have plenty of room so that’s not an issue.

The calculation then for the extra cost is (380 watt panels X 6 =) 2280 watts X about $2.50 per watt installed = $5,700 of extra solar needed to compensate for the hot water not switching to the hybrid (saving the $300/yr). After the 26% tax credit, that’s $4,218.

The hot water heater with the unit and labor would probably run close to $2,000. They also have a $300 federal tax credit, so net that’s $1,700. The difference is $4,218 for solar – $1,700 hot water heater = $2,518 more to not mess with hot water heaters and instead generate the extra power with solar to go netzero or offset it.

I hope I did the math right and will recheck it again tomorrow. Very cool to see though what the actual numbers. The payback on the whole project would jump up a little bit and we’d need to bringing the rest of the project numbers to figure that out.

– Erin Shine | Founder

From Rayanne:

I’ll take a look at this Erin, thanks.

I think I’m going to go with a standard water heater installed, mine is busted!! Timing is everything, but I did look at tankless and hybrid.

Electric supply & cost is the issue with tankless and the space and conditions I have are not suitable for hybrid so I’m thinking it will definitely be a solar offset.

Really appreciate your thoughts on this, I’m learning alot!

– Rayanne

What she meant by space conditions (for the heat pump water heater) is that due to it being in a closet in her kitchen, there wasn’t enough cubic space of airflow that the heat pump needed to work efficiently.

More importantly, though, the heat pump water heater makes a low hum fan noise. This can be quite annoying when it’s in your living area. We would have had to move it out to the garage and repipe a lot. So she opted for just a regular hot water heater and a few more solar panels, even if it wasn’t the highest ROI way to go.

This is an example of taking many goals, including regular home comfort, and making a gameplan going forward within budget.

a conventional hot water heater installed in a small kitchen closet space
This small enclosed closet area was right near the kitchen, which means a heat pump water heater would have made noise, and didn’t have enough airflow anyway.

Solar Time

We had looked at other potential projects, but I had known from my other personal netzero renovations at the time that the payback on solar itself in that area of Florida was about 8-9 years.

From an ROI standpoint, that also means that anything above that payback timeframe would have yielded a lower return on investment and higher payback period. That also means that if you have room for solar, it’s actually more prudent sometimes to add more solar and produce more power instead of save it.

While many in the building science world may not agree, from a pure real estate investor point of view, it makes a lot of sense. You’re also not upsetting the household nearly as much since it’s just outside on the roof, vs. tearing apart other parts of the house, among other things. The project can also go faster.

Now that we knew what our new rough baseline energy was going to be (after the efficiency upgrades and plan in place), we could now design for solar electric panels to be totally netzero.

Do We Also Power an Electric Car in the Future?

It’s good to note that we discussed adding enough solar to fully power an electric car in the future as well. This can have incredible financial benefits for both saving money yearly and heading against future oil prices, among other things.

For a few different reasons, including having the flexibility of adding more panels later for this, we opted not to do it on the initial project. Remember, we are operating on a retirement fixed income.

Solar Proposal

This part went much, much smoother than normally goes for the regular homeowner getting solar proposals. The reasons why are:

  • I already knew a reputable company in town.
  • They had quoted a very affordable price for my own netzero home project.
  • They have been around for almost two decades – no funny business.
  • They didn’t have to pay for marketing leads or commissions to anyone for the lead (me included – I did this project for free at the time).
  • Easy to work with, worked hard, and did a great install – I had already seen their good work.

The company is Florida Solar Design Group, and if you’re in the area, I highly recommend them. I hate to say it, but the solar industry has a really bad rap in areas, and Florida is one of them. It comes from the bad finance deals, skeezy marketing, and people just trying to make a buck at your expensive.

This is one reason why we offer a solar proposal review service, so that if you might have many quotes, or just want to the real deal on whether you really should do solar or not, you can at least have someone on your side without incentives to sell you an expensive solar system.

One huge point to using a reputable company like this, looking back, is that both Rayanne’s and my house survived Hurricane Ian without any damage to the solar panels on the roof. With a storm that size, I was astounded that this system held up. After two weeks of the electricity being off, the system started up like nothing had happened. Incredible.

It has to do with the quality of installation, components used, and the higher quality solar panels with higher pressure ratings. Everything was rated to withstand hurricanes, and it held up.

Here are some screenshots of the original solar proposal numbers:

a solar proposal showing what energy savings production would be vs. current energy usage for our netzero project

Between the discussion of all three of us (myself, Rayanne, and the solar company), we all settled on a 9.24kW solar system, for a total cost of about $16,600 after tax credits and other things. This would calculate to completely eliminate her bill after our efficiency work and new lower baseline usage.

a monthly graph showing the offset of energy usage vs solar production

We are also using net metering here, which sells unused power back to the utility, and your meter spins backwards and forwards. This eliminates the need for batteries (unless you still want power when the power is out), and keeps the cost low in comparison.

Here are some finished project pictures of the solar install, only about 3-4 weeks after receiving the proposal:

solar panels installed on a light grey house with a red brick patio in the front

A nice bonus is that the ideal solar panel orientation (southeast in our case) is on the back side of the house, leaving her front side looking the same from before. She preferred this look.

Nearly no one would see the back of her house with the solar on it. Different owners have different personal opinions on the look of panels, so it’s all subjective. I personally like the look and have them on the sides and front of my own netzero homes.

a light grey house with solar panels on the metal roof, displayed on the backyard with lots of green plants and trees around it

Conclusion and Testimonial

That’s pretty much it! There’s a bunch of other stuff that happened in between, but this shows you a bit of what our services look like, and what going netzero looks like affordably.

This was all done for under $19,000 with tax credits. That includes:

  • Blower door and duct testing.
  • Air sealing many different areas.
  • Adding, moving, or reinstalling insulation to be the most effective within our budget.
  • The complete solar panel system to go netzero.

Again, this was my very first project with someone else, and didn’t charge anything for consultation or overseeing the project. It was really just fun to do, and to help someone else achieve their goals of being total green (netzero) and also staying within a very, very reasonable budget with a fixed income retirement.

You can also do some investment numbers on how this went.

While the goal was really to be sustainable finally and netzero, the ROI (return on investment) can be calculated as:

$1,200~ per year savings / $19,000 project cost = 6.3% return per year.

This definitely beat what bonds paid at the time (2-3%) , and is basically risk-free. This was at the time of install, though.

Updated for today, electricity prices have gone up about 30% in the area. If we redo the calculations, they are:

$1,200 x 30% = $1,560 savings per year / $19,000 = 8.2% return per year.

I wanted to add in this year to show you what even a year or two of rate increases in an inflationary environment can do to your investment earnings.

By going netzero at a certain time in history, you’re effectively locking in and protecting yourself from future rate increases. Now when electricity rates go up, your effective ROI goes up as well, because of the fixed project cost in the past.

This is a very similar calculation to inflation hitting real estate with mortgage rates and home prices going up. But more on that part in other articles.

To finish it off, I’ll include Rayanne’s email to me as we wrapped it up. I’m so appreciative that she trusted me to work with her on this, even though it was literally my first one for someone else:


I cant even begin to figure out how to thank you for reigniting my energy conservation/solar efforts and teaching me about  the tools available like the blower door test.  The effort has been/is expensive but the timing, efficiency and costs are better than when I’d priced previously.

My ability to move forward so quickly was in large part because of your introductions to Florida Blower Door and Florida Solar Design Group.  Working with both groups was above and beyond what I’ve become acustomed to.  Turns out Jason from FSDG has roots on Sanibel and on our first visit it was like old home week.   

I’ve been playing around a bit and turned off the water heater for 2 days, still plenty of hot water, and i’ll text a screen shot that shows the big demand that hit this morning at 7 am when i turned it back on!!

I”m so impressed that you know how to do so much, sounds like you have found a new way forward, finding talented help and getting folks to show up really seems to be a crisis of its own across all industires so you are not alone!   

Thanks again and please let me know when you are in town again and I’ll show you what gets done in the guest suite.  

– Rayanne

Curious on doing a similar project with your own home? Feel free to reach out here. Thanks so much for your time and reading!

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