Updated: Dec 1, 2022
After several years of dreaming, hoping, and saving, my family and I embarked on a journey to build a modest but sustainable 'future-proof' home. One of the goals was obviously to have a solar energy system (our old home didn't). But, to also build a home that could be unplugged from the power grid, yet still maintain all of the normal creature comforts that most homes have nowadays. Additionally, we obviously needed to keep this on a modest budget and so my mission was to build a highly efficient home using standard construction practices that most builders utilize in this area. The result has been very satisfactory in operation, comfort, and efficiency and I wanted to share this with as many of you as possible.
First of all, if you are planning to build a home with the intention of installing a solar energy system, I highly recommend that you should think about design aspects of our roof and discuss these with your architect. Make sure you tell them that you plan to install solar panels on the south facing side and you want it to shaped rectangularly as much as possible. Please delete the dormers, hips, plumbing stacks, and chimneys on the south side, please. This will be the foundation of your 'power plant' and you really do need as much square footage here as you can get. My house was designed by architect Mike Shoulders using a salt box style design with a large rectangle on it's south roof. I highly recommend Mike as he designed some of the earliest solar powered homes in Indiana.
Front of home designed by Mike Shoulders, founder of VPS Architecture.
Since I intended to focus this article about the Tesla Powerwall and how it works, I will cut to the chase and give you a quick rundown on the other design aspects: poured wall foundation, 2x6 outer wall studs, spray foam insulation, standard windows, standard doors, gas furnace, gas cooking range, gas clothes dryer, gas tankless water heater, wood burning stove, 15KW solar energy system (Enphase), and (my favorite part) (2) Tesla Powerwall's. To summarize, just a standard yet efficient home powered by a grid-tied solar energy system with battery backup.
So, how does it work? During the daylight hours, the solar energy system is generating electricity. The home will consume some the generated solar energy as first priority. Secondly, any excess will be used to charge the Powerwall's until they are full. Thirdly, when the Powerwall's are full, any Excess Distributed Generation (or EDG) will flow back to the grid. So, each morning when the sun comes up, the Powerwall's will be topped off automatically to make sure they are full. I generally keep mine set for Backup Mode Only, which means that the batteries stay full most of the time until there is an emergency power outage.
For some customers that do not have net-metering, you can also operate in Self Supply Mode. In this setting the Powerwalls will store energy during daylight hours until they are full, and then release some of the energy into the house after the sun goes down. This allows the home owner to store and consume as much of their solar generated energy as possible to minimize the amount sent back to the grid. You can also set the Powerwall to release the energy during different times of the day or night if desired, to offset any large loads or charge vehicles. So, this gives some additionally functionality when in use with a Tesla automobile.
Two Tesla Powerwall 2's.
Yes, my electric bill stays at $15.00 per month with plenty of KWH in the bank. We do have a gas bill which had increased dramatically last winter. So, we did try to consume some of our banked KWH's by utilizing electric space heaters plugged into outlets, and this works out quite well. For the most part, two small space heaters would heat the house and this is an easy way to heat with solar PV if you want. It's better to use them during daylight hours. We also have a wood burning stove in the basement as another source for heat. As most of you know, wood heat is not free heat, but it's nice to have as a backup. I am actually planning to install a larger 240V electric heater in the basement for next winter.
The Tesla Powerwall app tells you what is going on at all times.
The end result? It is very ensuring and comforting to know that my family will have electricity during the next emergency power outage. No spoiled food, no cold showers, and plenty of air conditioning. Whether it is caused by an ice storm, tornado, or rolling blackout, the Tesla Gateway will automatically detect it and shift the Powerwall's into gear. And, this happens in the blink of an eye and rarely is noticed inside the house. The TV's and appliances continue to operate and have never shut down during the extensive testing that I have performed. I have also tested the operation of our air conditioners in off-grid mode and they have ran fine so far. These are typically the biggest loads that should be operated in off-grid mode due to the high startup current of AC motors, and an engineering study should be performed on each home to make sure the Powerwall(s) can handle the loads.
If you would like more information about the Tesla Powerwall's, feel free to give us a call or visit our website to request a quote. They are truly amazing!