How To Get Off The Grid

Selling excess power is only part of what makes the economics of home-produced energy work, and it turns out it's not a very big part. PG&E sells you power at retail rates (30 to 40 cents per kWh) but buys it back at wholesale rates (2 to 3 cents per kWh). So it's really not in your financial best interest to overproduce energy. If I sold the entirety of the best day's production of my home's solar energy back to PG&E, I wouldn't even earn a dollar.

A much bigger incentive, however, is the fact that the government will pay you to install this stuff.

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There are two major rebates. First is a federal investment tax credit, and while it once involved a complicated system of rebates, it was recently overhauled: Install solar (with or without a battery) and you get a fat credit on next year's income taxes. Last year the credit was 30 percent of the total installation cost. This year it's 26 percent. Next year it goes down to 22 percent. After that, the credit goes away completely, unless Congress acts before then. It's a simple credit—a single form that you file with your tax return—but we won't see that value until 2021.

The second rebate is from California's Self-Generation Incentive Program. This program is administered by PG&E, and it is really built to encourage energy storage instead of simple production, which for most homes means a battery. The rationale behind SGIP is that there is so much solar power in California that the state can't use it all. On especially sunny days, PG&E actually has to pay other states to take excess power so as not to overload the grid. But when the sun goes down, the situation changes dramatically. Without all that solar, gas-powered "peaker plants" have to be fired up and run until demand dies down, which is why most PG&E rate plans charge you more for electricity use in the evening. The upshot: PG&E will subsidize your battery to avoid those off-hour energy production costs.

The SGIP is a moving target, but at present the rebate is $250 per kWh of storage—$3,350 for my installation—and it's cash back. The catch? The SGIP, which is outlined in a 139-page handbook, is so complex that your installer has to file all the paperwork for you. The process, I'm told, will take up to a year before I see a check. At press time, I'm still waiting.

It Ain't All Sunshine and Roses

Aside from the up-front costs—which merit serious analysis before you jump into this process—what are the other downsides of installing a hybrid solar-and-battery solution? So far, I've found more than a few. I'll explain.

I'm not saving anywhere near the amount of money I was promised.

During the research phase, I received a detailed, personalized analysis that estimated my average electric bill would drop from $223 to $22 a month. Though my May 2020 bill was just $86 (down 54 percent versus the prior year), and my October 2020 bill (which was the first to include net energy metering) was $78 (down 60 percent), some of my bills during the hotter months were higher than in 2019. (Of course, everyone working and schooling at home has caused us to use more energy this year.) That said, I'm definitely not seeing a $22 electric bill and really don't expect to get one. If my net savings going forward hold at 60 percent—a very optimistic number—it pushes my expected payback period out considerably, from breaking even in nine years to breaking even in about 17 years.

You can't run the whole house with the battery.

This is a biggie. You'll have to pick and choose which circuits your battery can provide power to, both after hours and during a blackout. The main reason for this is an amperage limit: My inverter can handle only 23 amps of draw. Our refrigerator alone pulls 5 amps.

We ended up having to install a second electrical panel—the critical load panel—which has just eight circuits out of the 40 from the main panel connected to it. After hours, these circuits and only these circuits run off the battery. The rest of the circuits in the house have to draw from the grid. And in an outage, they go totally dark. The good news is that I could pick the eight circuits I wanted to back up (though one of them had to supply the inverter's electronics, leaving just seven to play with). This wasn't too difficult. Most homeowners choose to back up circuits that power their refrigerator, wireless router, garage door openers, and a smattering of lights and small appliances, and that's what we did. In a blackout, the circuits I picked would still provide a comfortable living situation. The major home conveniences that the system doesn't back up are the air conditioner, ovens, washing machine, and dishwasher. (Our water heater and furnace are powered by natural gas.)

Battery charging is problematic in the fall and winter.

In the summertime, there's so much sun that my battery is usually recharged before noon. As of November, there's so little sun that it takes most of the daylight hours to recharge, and on cloudy days it often doesn't recharge fully at all. Instead of the 35 kWh I produced on June 25, I'm now producing about 11 kWh per day. That means more reliance on the grid and, of course, higher energy costs.

The inverter app just doesn't paint a good picture of your energy usage.

The Electriq power management app and website dashboard are sexy with all their charts and graphs, some of which I'm including here. On most days I see a big rush of solar production and a spike of "grid export" in the afternoon, with my battery kicking in after hours.

Courtesy of Christopher Null