Rooftop solar, a heatwave, and the grid!



California has major challenges around our power grid. California’s 40 million people use massive amounts of power. The grid’s job is to ensure all of those people have a constant supply of power 24 hours a day, 7 days a week, 365 days a year. Our grid extends across varying terrain. Consumers also aren’t always consistent in how and when they use power making the grid operator’s job all the more complex. We currently experience two different known interruptions to our power.

Revisiting PSPS

Last year PG&E (and other operators) introduced a new term in everyone’s vernacular: PSPS. PSPS is short for public safety power shutoffs. A PSPS event usually happens around a confluence of a few events. These events include:

  • 4-6 months without rainfall so all the vegetation is easily flammable
  • incredibly low humidity (sub 30%)
  • windy in areas around significant power grid infrastructure

Should a power line break due to the wind, the fire that results from the spark will easily spread. By de-energizing the lines, no fires will result from broken electrical infrastructure (e.g. tree falling on the wires, etc). These events are designed to limit the transmission of power through brittle areas that are known to cause wildfires.

Remember the rolling blackouts?

Report from the CA ISO for 8/24/20 20:00

Today California’s grid operator (CA ISO) has instructed the state’s utilities to reinstitute rolling blackouts. We’ve not seen rolling blackouts since 2001. The reason? Much of the state is in a heatwave and the demand for power is exceeding the supply. Rolling blackouts are designed to keep the grid stable under such strain. It’s important to note that a PSPS event and rolling blackouts solve different challenges. A PSPS event is designed to prevent wildfires from physical damage to the grid. Rolling blackouts distribute the limited supply of power across the grid.

Revisiting farm to table

There are a lot of parallels in power from farm to table in the culinary world. Obviously, food doesn’t come from the grocery store. The grocery store is just the point-of-purchase. Farmers utilize a variety of techniques to produce food. Distributors move food from the farm, through various distribution sites, and eventually to the consumer. The less distance between the farmer and the consumer the “greener” the consumption of food becomes.

Power, much like food, benefits by reducing the distance between the generator and the consumer.  Much like farm to table in the culinary world, there are benefits in reducing the amount of distance power has to travel between the generator and the consumer. I’ve long been a fan of solar. With solar panels, the generation of power is close to the consumption of power.

The element of when

I wanted to understand how my solar panels might play a role in reducing the impact of rolling blackouts. For the two years I’ve had solar, I login occasionally in track my overall impact on the grid. In August 2020, I’m a net contributor. I am pushing more power to the grid that I am taking. The days are long in summer so a net surplus is expected.

On Thursday, August 13 we had an exceptionally hot 100° day. That’s the tiny blue bar showing I was a net consumer that day. I wanted to do a little bit more research and understand more closely how I was using power. Looking at my power provider’s website for just that day, it’s clear I use more power in the evenings.

But even this view, is only telling part of the story. I’m not seeing my true demand for power I’m only seeing my net consumption or production to the grid. I wanted to see how I was using power over a few different days and understand if and how my rooftop solar was helping the grid.

I took three days of data and came up with a couple of conclusions. Pulling the same data from my solar provider I could get a much better picture of my total power footprint. Let’s take a look at the breakdown of those days.


  • Structure of the house is cooler as temps have been cool at night
  • I was gone during the day so Nest did not turn on A/C until I came home.
  • When I got home, I plugged in the car to begin charging.
  • I accidentally told Google Assistant to turn Nest off (hence the rise in temperature)


  • We are in day 2 of a massive heat wave so the structure of the house is warmer, requiring air conditioning at night.
  • Air conditioner is enrolled in Smart AC which cycles the air conditioner to run no less than 30 minutes each hour during peak periods
  • I am at home all day so Nest is assuming it needs to run climate control all day.


  • Structure of the house is likely warmer due to the 106 degree high Saturday.
  • Air conditioner is not enrolled in Smart AC as a comparison for power usage over the afternoon
  • I am at home all day so Nest is assuming it needs to run climate control all day.
  • At 5am house feels warm so I kick on the air

Immediate Outtakes

Rooftop solar turns me into a net producer most of the day. My solar panels are exporting power to the grid to be used by my neighbors without solar. This is a win. From 5 PM to 10 PM, however, I’m using more power to cool the house. I get strong, western sun that requires the air conditioner to run a good portion of the afternoon and evening. On days when the grid needs power, solar does help make things easier. However, there are a few other items of note:

  1. I start pulling from the grid a few hours before sunset. Pre-cooling the house uses more of the power I have vs pulling more from the grid later.
  2. Configuring my car charger to not charge during peak rate periods also keeps me from accidentally pulling power during peak times.
  3. Smart A/C seems to work. Having my AC controlled by the power company feels big brother-ish but it did save me power during the peak window.

The challenge here is the same as I have with managing my diabetes. None of the devices talk to one another. With a truly connected home and grid, some neat things open up. A smart thermostat could cover #1 by building a demand profile for my house over time. Likewise, the car charger could communicate to the grid on when to optimally charge a car. I miss the fact that my Juice Box doesn’t have a button to override not charging during peak periods. That is the reason I don’t enable it.

Using power better

The good news is the solar panels do offset some of the afternoon power demand – but not all of it. This chart makes it clear to me that solar alone is not the complete solution to our power challenges. Batteries like the Tesla Powerwall make it easy to store power to reduce the need to pull power from the grid when solar panels don’t produce enough power. Unfortunately, batteries are also relatively expensive per kilowatt.

In Amsterdam, the grid operator is placing battery banks within neighborhoods. These battery banks help reduce the strain on the grid during peak consumption at a neighborhood level. Also, electric cars becoming more common manufacturers could make it easy to pull power from the car during a power outage. I think we’ll be seeing a lot more innovation in this area over the next decade.

I could also start cooling the house earlier to make better use of the solar panel’s energy. It would be great if the Nest could pre-cool the house while solar power is freely available and then raise the temperature to reduce the demand for air conditioning later in the afternoon.

I do think we’re going to see some pretty incredible changes in how we generate, store, and consume power. The main limiting factor is battery storage. The faster we develop, deploy, and recycle batteries the less reliant we become on petroleum for energy.

I’m still happy with my solar. I think it’s a great investment for homeowners to have better control over their energy destiny. That being said, however, the better we can use power both individually and collectively the stronger the grid in the community served by it.


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