Powering through Blackouts with Solar and a Battery
With an increasing number of severe weather events across the world, including most recently Hurricane Ida and several powerful storms across the Midwest, people are looking for ways to build resilient sources of energy. My neighborhood in Ann Arbor, Michigan experiences frequent power outages, and in recent years more and more of our neighbors have installed natural gas generators to avoid losing refrigerators full of food, sitting in the dark, and generally being miserable for hours on end. While a bit quieter and certainly more convenient than free-standing generators, the ~$10k investment became less appealing as we learned about whole home electrification backed by renewable energy sources like solar.
In March of this year, my husband and I completed the installation of our 4.5kW solar array with a Tesla Powerwall battery that stores excess power for use at night and during outages. Beyond storing energy, the Powerwall makes it possible for us to continue drawing solar during a grid outage —believe it or not, a standard solar system does not function during a grid outage. With grid-tied solar, when the grid is functioning, any excess power generated by solar is fed back into the grid (in our case resulting in half-rate credit on our electric bill) for use by others. When the grid goes down, the utility company also stops the solar from functioning to protect the safety of workers repairing the lines. The brilliance of a battery backup like the Powerwall is that when the grid power is out, it creates a microgrid that continues to power your house. I don’t know about you, but I’d be maniacally frustrated to be without power when I have the capability on my roof to produce it. So, yeah, we got the battery system.
In just six months, this setup has gotten us through 11 separate outages, totaling 91 backup hours with basically no noticeable impact on our living, including a recent outage that lasted 83 uninterrupted hours.
The clocks didn’t blink “12:00,” the wifi didn’t interrupt, and the lights didn’t flicker. We lived our lives essentially as we normally would, which during pandemic times includes working from home. We also charged a portable battery pack for my in-laws (they, too, were without grid power), ran the dishwasher, and washed a few loads of laundry that included — yes — powering the dryer. Here’s how we were able to do it and what we learned.
High-wattage devices are not connected to the battery and, hence, can not be powered in an outage.
Because we only have a single Powerwall, we can’t have “energy-intensive” appliances connected to it. In our household this is the electric oven and the air conditioner. Until recently, it included a dryer, but then we switched to a heat-pump version (more on that in a minute). My understanding is that additional Powerwalls (2–3) can be connected together to enable the use of high-wattage appliances. We may consider that in the future as we further electrify our house, but for now one completely suffices.
Efficient lights and appliances helped a lot
The Tesla Powerwall app makes it easy (and fun after you have transformed into a home energy nerd) to observe the energy impact of turning particular things on and off. Common sense tells you that the less energy-demanding your things are, the more you’ll be able to use for a given measure of energy. But being able to see in real-time that whenever you turn on the microwave, your usage shoots up 300% makes efficiency more than conceptual.
We use only LED lightbulbs, and the vast majority of our appliances are high-efficiency, including the refrigerator, dishwasher, and dryer. The dryer was a recent purchase inspired by watching our energy use spike to absurd levels (something like 6kW) when we turned on our old, standard electrical dryer. Our new Miele heat-pump dryer draws closer to 1kW and is plugged into a standard 120V outlet that is connected to the Powerwall system. During the 83-hour outage, the most consistently “large” draw on our energy was the dehumidifier. Even though it is energy star-rated, left on, it would have run constantly to maintain a humidity level below 50% in the basement.
We were conscientious about our energy use but did not suffer
In the multi-day grid outage, we became very aware of the energy we had stored and our dependence on the sun for producing more. As a result, we watched our usage, battery level, and solar production frequently and took steps to minimize our draw where possible.
Solar Production Day-by-Day During 4-Day Blackout
Day 1: 18.2 kWh
Day 2: 12.9 kWh
Day 3: 20 kWh
Day 4: 17.1 kWh
We turned off lights and fans in rooms we weren’t using, turned off power strips to appliances not being actively used (e.g. printer, stereo system), and turned off our dehumidifier at night. This was especially important the first two days given the relatively low solar production day on Day 2. But beyond being more conscientious, we really didn’t lack for power and we lived pretty normally, making coffee, using the microwave, cooking dinner (gas range), using lights, charging devices, and working from home.
And, when we saw we were producing more energy than we were using with no means to distribute it back to the grid, we were motivated to make use of it! That meant using the washer, dryer, and dishwasher during the day. In fact, by Day 3, when we were producing enough excess energy that the Powerwall began to turn off the solar system (it does this until the battery runs down enough to collect more), I was texting neighbors and friends to come over and charge their devices.
We’re still learning
We’re still going through our first full year on solar, and I expect to learn more as we live with the full four seasons of Michigan’s northern climate. We were somewhat fortunate that our 83-hour outage coincided with several days of relatively mild summer temperatures and sunny skies. We comfortably lived without air conditioning by running fans and closing windows and doors during the hottest part of the day. In August, the days are still long and mostly sunny; we have yet to see what kind of solar production is more typical of the short days of late fall and winter. Regardless, I feel relief to be less vulnerable to grid outages than we once were and joy at the technological miracle of silently and seamlessly generating my home’s power with the beautiful, shining sun.
Big shoutouts to Ann Arbor Solarize, CBS Solar, and AJ Leo Electric and Solar, who made all of this possible for us!
