The Solar Shade Control Act: When a Neighbor's Solar Panels Limit Your Trees

A letter arrives from the neighbor's lawyer. It cites the Solar Shade Control Act, says your redwoods are shading their new rooftop array, and demands you cut them. I have been called in on several of these, and the first thing I do is read the statute, because the letter usually overstates it. The Act is short, seven sections, and most of the questions in a tree-versus-panel dispute are answered by two of them: which came first, and whether a city ordinance already covers the tree. This guide goes through the text section by section, with each number taken from the code as published on leginfo.legislature.ca.gov on October 12, 2026.

The 10 Percent Rule: Section 25982

The operative sentence is section 25982: "After the installation of a solar collector, a person owning or in control of another property shall not allow a tree or shrub to be placed or, if placed, to grow on that property so as to cast a shadow greater than 10 percent of the collector absorption area upon that solar collector surface at any one time between the hours of 10 a.m. and 2 p.m., local standard time."

Four details in that sentence decide most disputes. The duty begins "after the installation," so timing is everything. The measure is 10 percent of the "collector absorption area," meaning the panels' active surface, not the roof. The test is "at any one time" within a four-hour window, so a shadow that crosses 10 percent of the array for ten minutes at 10 a.m. is enough. And the window is stated in "local standard time." My reading, and I flag it as mine, is that the window does not shift with daylight saving time, so during summer the statutory 10 a.m. to 2 p.m. corresponds to 11 a.m. to 3 p.m. on the clock. That matters because shadow angles change by the hour.

The Act opens with a statement of policy in section 25980 that is worth quoting back to anyone who treats it as anti-tree: "the state encourages the planting and maintenance of trees and shrubs to create shading, moderate outdoor temperatures, and provide various economic and aesthetic benefits. However, there are certain situations in which the need for widespread use of alternative energy devices, such as solar collectors, requires specific and limited controls on trees and shrubs." The controls are described by the Legislature itself as "specific and limited."

What Counts as a Solar Collector: Section 25981

Not every panel qualifies. Under section 25981(a), a "solar collector" is "a fixed device, structure, or part of a device or structure, on the roof of a building, that is used primarily to transform solar energy into thermal, chemical, or electrical energy" for water heating, space heating or cooling, or power generation. Subdivision (b) extends the definition to a ground-mounted collector only where a rooftop collector "cannot be installed on the roof of the building receiving the energy due to inappropriate roofing material, slope of the roof, structural shading, or orientation of the building." Subdivision (c) excludes a collector "designed and intended to offset more than the building's electricity demand."

Subdivision (d) adds siting rules the collector owner must meet to claim the Act's protection: the collector must comply with local building and setback regulations, be "set back not less than five feet from the property line, and not less than 10 feet above the ground." A collector lower than 10 feet qualifies only if, in addition to the 5-foot setback, it "is set back three times the amount lowered." A panel installed on a low shed at the fence line may not be a protected collector at all.

The Exemptions: Section 25984

Section 25984 says the chapter "does not apply to any of the following," then lists four categories:

• "(a) A tree or shrub planted prior to the installation of a solar collector."
• "(b) A tree planted, grown, or harvested on timberland as defined in Section 4526 or on land devoted to the production of commercial agricultural crops."
• "(c) The replacement of a tree or shrub that had been growing prior to the installation of a solar collector and that, subsequent to the installation of the solar collector, dies, or is removed for the protection of public health, safety, or the environment."
• "(d) A tree or shrub that is subject to a city or county ordinance."

Subdivision (a) is the one most homeowners need. If your tree was in the ground before the neighbor's array went up, the Act does not reach it, no matter how large the tree grows. Note the word is "planted," not "mature" or "tall." A 15-gallon redwood planted in 2015 that now shades a 2020 array is exempt. Subdivision (c) protects your right to replace that tree if it dies or has to come out for safety. Subdivision (d) is broader than most people realize and I come back to it below.

Section 25985 gives local governments two more levers. Under (a), a city or county "may adopt, by majority vote of the governing body, an ordinance exempting their jurisdiction from the provisions of this chapter." Under (b), "a city or a county ordinance specifying requirements for tree preservation or solar shade control shall govern within the jurisdiction of the city or county that adopted the ordinance." I have not verified which Bay Area cities, if any, have adopted an opt-out ordinance under 25985(a); treat that as unverified and ask your city attorney's office.

The 2008 Amendment: From Crime to Private Nuisance

The Act dates to 1978 (Stats. 1978, Ch. 1366). Its one major overhaul was SB 1399 by Senators Simitian and McClintock, chaptered July 22, 2008 as Chapter 176, Statutes of 2008, effective January 1, 2009. Some summaries attribute the change to "AB 2321"; that is wrong. AB 2321 of the 2007 to 2008 session was a Los Angeles County transportation funding bill (Chapter 302). The Legislature's record describes SB 1399 as "An act to amend Sections 25981, 25982, 25984, and 25985 of, to add Section 25982.1 to, and to repeal and add Section 25983 of, the Public Resources Code."

The re-enacted section 25983 now reads: "A tree or shrub that is maintained in violation of Section 25982 is a private nuisance, as defined in Section 3481 of the Civil Code, if the person who maintains or permits the tree or shrub to be maintained fails to remove or alter the tree or shrub after receiving a written notice from the owner or agent of the affected solar collector requesting compliance with the requirements of Section 25982." Two things follow. The remedy is a civil nuisance action between neighbors, not a prosecution. And the nuisance does not arise until the tree owner has received written notice and failed to act, so there is always a chance to prune or negotiate first.

I did not retrieve the pre-2009 text of section 25983 from a primary source, so I rely on contemporaneous reporting for what it said. The ABA Journal reported on February 22, 2008 that the earlier version allowed fines of up to $1,000 a day and had just produced its first conviction. That is background, not a statement of the current law, which contains no fine and no criminal provision.

The Optional Advance Notice: Section 25982.1

SB 1399 also added section 25982.1, which lets a building owner who is about to install a collector send a "SOLAR SHADE CONTROL NOTICE" by certified mail to neighbors "that may be affected." The notice "shall be mailed no more than 60 days prior to installation" and must state the installation date, the building address and parcel number, and the owner's contact information. The statute says the owner "may" send it; it is not a precondition to the Act's protection. But if you receive one, keep it. It fixes the installation date, which is the date that decides whether your existing trees are exempt under 25984(a). Anything already planted on that date is outside the Act. Anything you plant afterward is not.

City Tree Permits Still Apply

Suppose the neighbor wins. A court finds your tree was planted after the array, finds the shadow exceeds 10 percent in the window, and orders abatement. You still need your city's permit before the tree is pruned or removed if it is a protected tree. Nothing in the Act waives local permits, and 25985(b) says the opposite: a local tree preservation ordinance "shall govern." A judgment tells you what result to reach; the city tells you what process to follow to reach it. In practice, the court order becomes the removal justification on the application, and in several cities it may still be denied or conditioned.

Section 25984(d) goes further and removes "a tree or shrub that is subject to a city or county ordinance" from the Act altogether. I have not found a published court decision interpreting that phrase, so I will not tell you how far it reaches. On its face, a protected tree in a city with a tree preservation ordinance is a strong candidate. The thresholds from my 45-city ordinance table show how many trees that could be:

Protected tree thresholds in selected Bay Area cities

City	Protected tree threshold
Palo Alto	Six native species at 11.5 inches DBH; coast redwood at 18 inches DBH; all other non-invasive, non-high-water-use species at 15 inches DBH (PAMC 8.10). Pruning a protected tree requires a 7-day posted notice.
Sunnyvale	Any species at 38 inches circumference (about 12.1 inches diameter) (SMC 19.94).
San Mateo	Oaks at 10 inches diameter; any other species at 15 inches diameter (SMMC 13.40). Pruning more than 25 percent of the crown is "major pruning" and needs the same permit.
Redwood City	Any species at 38 inches circumference (about 12.1 inches diameter) (RCMC Ch. 35). Pruning a protected tree needs a free permit.
Los Gatos	12 inches diameter single trunk on developed residential lots; pruning permit for more than 25 percent over 3 years or any branch over 4 inches.
Menlo Park	Heritage trees under MPMC 13.24; removal or significant pruning requires an arborist report from a city-approved consulting arborist.

Two more local wrinkles. Berkeley's coast live oak moratorium (BMC 6.52) has no shade exception; removal requires a City Manager finding of potential danger to life or limb. And Tiburon has its own View and Sunlight Obstruction ordinance (TMC Ch. 15), a separate local track that can reach trees the state Act does not. Check your city with the Permit Checker before responding to any demand letter.

Background: The 2008 Redwoods Case

The case everyone cites is from 2008 and predates the amendment. I present it as background only, from contemporaneous news coverage rather than the court file, which I did not retrieve. The ABA Journal reported on February 22, 2008 that a California judge found two of a couple's redwoods had grown large enough to violate the Act and ordered them cut, in what was described as the first conviction under the then 30-year-old law, with no fine imposed. ABC7 News covered the same dispute between homeowner Richard Treanor and neighbor Mark Vargas, who had installed the panels, and reported that Senator Simitian had proposed a bill to let trees planted before the panels stay. That bill became SB 1399. The two accounts differ on whether one or two trees were ordered cut. Secondary accounts place the property in Sunnyvale, in Santa Clara County, and say the trees were planted before the panels but grew into violation afterward; I could not verify those details against a primary record, so treat them as reported, not confirmed.

The lesson that survived into the current statute is the planting-date exemption. Under today's 25984(a), a tree planted before the collector is simply outside the Act, regardless of when it grew tall enough to shade.

What an Arborist Report Documents

In a solar shade dispute the facts are physical and datable, which is why both sides end up hiring an arborist. The report I write for these cases, through the dispute and appraisal service, documents five things.

Planting date evidence. Trunk diameter, species growth rate, nursery stock size, planting receipts, permit records and dated aerial imagery, assembled to show whether the tree predates the collector under 25984(a). This is usually the whole case.

Shadow measurement. Where the shadow falls on the collector surface at intervals between 10 a.m. and 2 p.m. local standard time, on the dates in question, and what fraction of the absorption area it covers. Ten percent is a measurable number, and a photo at noon in June does not prove a violation in December.

Collector qualification. Whether the array is on the roof, or ground-mounted with a documented reason, whether it meets the 5-foot setback and 10-foot height in 25981(d), and whether it appears sized beyond the building's demand.

Pruning alternatives. Whether crown reduction or selective thinning can bring the shadow under 10 percent while keeping the tree healthy and structurally sound, with an ANSI A300 specification and an estimate of the percentage of live crown removed. That percentage matters because San Mateo, Los Gatos and others regulate pruning above 25 percent.

Protected status and permit path. The tree's species and size against the city threshold, which permit applies to removal or pruning, and what the city requires in the application. Where the tree has appraisal value at stake, I add a CTLA appraisal so that any negotiated outcome reflects what the tree is worth.

If You Receive a Shade Complaint

Step 1: Establish the two dates. When was the collector installed, and when was each tree planted? If the trees came first, 25984(a) ends the inquiry. Gather receipts, photos, permits and imagery before you respond.

Step 2: Check whether the collector qualifies. Roof-mounted, 5 feet from the property line, 10 feet above ground or set back three times the shortfall, and not sized beyond the building's demand (25981).

Step 3: Check whether the tree is protected. Run your city in the Permit Checker. If the tree is protected, 25984(d) may take it outside the Act, and in any event the city permit governs the work.

Step 4: Measure the shadow. Have the 10 percent test done properly, in the statutory window, across seasons if the complaint is seasonal.

Step 5: Respond in writing. The nuisance under 25983 arises only after written notice and a failure to act. If the tree is not exempt and the shadow does exceed 10 percent, a pruning proposal that meets the threshold is a complete response; removal is not required where pruning works.

Step 6: Pull the permit before any cut. Whether you prune voluntarily or under a court order, a protected tree needs the city's permit first. The penalties for skipping it run from hundreds of dollars per tree to appraised-value fines and misdemeanor charges.

Frequently Asked Questions

How much shade is allowed on a neighbor's solar panels in California?

Under Public Resources Code 25982, a tree or shrub placed after a solar collector was installed may not cast a shadow greater than 10 percent of the collector absorption area on the collector surface at any one time between 10 a.m. and 2 p.m. local standard time. Shade outside that window, or shade from a tree planted before the collector, is not restricted by the Act.

Does the Solar Shade Control Act apply to trees planted before the solar panels?

No. Section 25984(a) states the Act does not apply to "a tree or shrub planted prior to the installation of a solar collector." Section 25984(c) also exempts the replacement of such a tree if it dies or is removed for public health, safety or environmental reasons. The test is the planting date, not when the tree grew tall enough to shade the panels.

Can I be fined or prosecuted for shading a neighbor's solar panels?

Not under the current Act. Since January 1, 2009, when SB 1399 (Stats. 2008, Ch. 176) took effect, section 25983 makes a tree maintained in violation of section 25982 a private nuisance under Civil Code 3481, and only after the tree owner receives written notice from the collector owner and fails to remove or alter the tree. The remedy is a civil action between neighbors. The statute contains no fine and no criminal penalty.

Can my neighbor make me cut down a protected tree to clear their solar panels?

Not without the city's permit, and possibly not at all. Section 25984(d) exempts "a tree or shrub that is subject to a city or county ordinance" from the Act, and section 25985(b) says a city or county tree preservation ordinance "shall govern" in that jurisdiction. Even where a court orders abatement, a protected tree in cities such as Palo Alto, San Mateo, Sunnyvale, Redwood City or Menlo Park still needs the city's removal or pruning permit before any work, and pruning that brings shade under 10 percent is often enough.

Does the Solar Shade Control Act apply to ground-mounted solar panels?

Only in a narrow case. Section 25981(a) defines a solar collector as a device on the roof of a building. Subdivision (b) extends the definition to a ground-mounted collector only where a rooftop collector cannot be installed because of inappropriate roofing material, roof slope, structural shading or building orientation. Any collector must also be set back at least 5 feet from the property line and at least 10 feet above the ground, or set back three times the amount it is lowered.

Sources checked October 12, 2026: Public Resources Code 25980 to 25986; SB 1399 (2007 to 2008) bill status; AB 2321 (2007 to 2008) bill status; ABA Journal, Feb. 22, 2008 and ABC7 News archive (background only); city thresholds from this site's verified ordinance dataset.