What Bright Saver's California plug-in solar pilot found
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The short answer: Bright Saver reports that an 800 W kit on an Oakland deck made and used about 2 kWh a day, saving about $27 a month: a 7.3 years payback at full price.[source]
About the pilot
Bright Saver, a nonprofit that sells plug-in kits, has run a subsidized plug-in solar pilot in California since early 2025. Its kits had backfeed-prevention hardware, which stops any power flowing to the grid. It reported these results in its white paper of October 2025, before SB 868 passed.[source]
These are Bright Saver's own figures, from a pilot it ran and partly paid for. We haven't checked them independently.
One household: Terry in Oakland
Terry is a retired man in his seventies on a fixed income. He needed a new roof before rooftop solar made sense, and asked: "will I live long enough for the investment to pay off?" Bright Saver volunteers installed a kit on his deck in March 2025.[source]
According to readings from his kit, it made and used about 2 kWh a day, which Bright Saver says saves him about $27 a month at his current electricity rate.[source] Bright Saver's comparison, at prices without tax credits or incentives:[source]
| System | Price | Savings a month | Payback |
|---|---|---|---|
| 800 W plug-in kit at full market price | $2,364 | $27 | 7.3 years |
| The same kit at Bright Saver's subsidized price | $1,772 | $27 | 5.5 years |
| Average rooftop system in the San Francisco Bay Area (EnergySage, as cited) | $20,862 | $232 | 7.3 years |
The kit's full market price includes mounting and installation. Bright Saver also argues that rising rates would shorten the payback, but the figures above use today's rates.[source]
What other households said
Bright Saver says most pilot households had considered rooftop solar but found it out of reach, because of cost, an unsuitable roof or renting, and that rising bills were the common reason they signed up.[source]
- Tiffany, a homeowner in Richmond, chose plug-in solar because of the total price: "We aren't quite ready to splurge on roof units."[source]
- Sean, a renter in Concord, couldn't persuade his landlord to install rooftop solar and works from home: "I did the quick math and figured that at least for the summer, it becomes worth it."[source]
How this compares with our calculator
For a well-placed kit (our "Typical" placement), our calculator expects 800 W of panels to make about 2.4 kWh a day, about 2.2 kWh of it used at home. Terry's reported 2 kWh a day is close to that, so our estimate looks reasonable for a kit like his. Your own result depends on your rate plan and where the panels face. Try the calculator with your utility and placement, and see plug-in vs rooftop solar for how the costs compare.
Frequently asked questions
- Who ran the pilot?
- Bright Saver, a nonprofit that sells plug-in solar kits. It ran the pilot, paid for part of each system and reported the results itself, in its October 2025 white paper.
- Will I get the same savings?
- Not necessarily. Savings depend on your rate plan, where the panels face, shade and how much of the power you use at home. Try the calculator with your own utility and placement.