Most solar advertising calendars are still built on two assumptions. That demand follows the sun, and that urgency follows the tax credit. Both stopped being true within the last year.
The tax credit assumption died on a specific date. The 25D residential credit expired December 31, 2025, and the run-up to it did something more disruptive than removing an incentive: it borrowed the following year's demand. The number of homeowners actively working with installers rose 205% in the second half of 2025 against the same period in 2024.
Those were not extra customers. Those were largely 2026 customers, buying early.
The short answer
Advertise against the driver, not the season.
| Driver | When it peaks | What to sell against it |
|---|---|---|
| Utility bill shock | Winter and mid summer, regionally | Payback and rate escalation |
| Outage and storm risk | Regional storm season | Battery storage, resilience |
| Rate structure changes | Utility filing dates, not months | Time of use optimisation, storage |
| Roof replacement | Spring and early autumn | Solar-ready roof, combined install |
| Tax and rebate deadlines | State and utility programs only | Remaining local incentives |
Notice what is missing: irradiance. Homeowners do not buy solar because it is sunny. They buy it because a bill hurt, the power went out, or a contractor was already on the roof.
Why the old calendar broke
The traditional advice was to spend heavily into spring, ride summer, and coast through winter. That calendar worked because it matched two real things: homeowners think about electricity in the cooling season, and the federal credit created a year-end deadline that made Q4 convert.
By the numbers
Wood Mackenzie forecasts residential solar volume down 21% in 2026. Meanwhile homeowners actively engaged with installers rose 205% in H2 2025 as the 25D deadline approached. A shrinking year, immediately after a borrowing spree, is a difficult combination for anyone whose calendar assumes normal seasonality.
The 21% contraction and the 205% surge are the same event viewed from two sides. Demand did not disappear evenly across 2026. It was concentrated into late 2025 and then left a hole.
This is also why Q1 2026 confused people. Installations were being completed from a backlog of customers who signed in 2025 to beat the deadline, alongside overflow interconnections. Revenue looked acceptable while new sales did not, and installers who read Q1 as a healthy market kept spending into a demand curve that had already been harvested. If your leads stopped converting while your spend held steady, why are my solar leads not converting covers the mechanics underneath that.
The calendar that actually works now
Winter, roughly December to February. The contrarian buy. Utility bills peak in most markets, resilience is salient after winter storms, and competitors have pulled back on the assumption that solar is a summer product. Auction pressure drops while the strongest emotional trigger, an expensive and unreliable bill, is at its annual maximum. This is where storage sells best.
Spring, March to May. Legitimately strong for new installs, and also the most expensive traffic of the year. Bid here, but expect to pay for it, and expect every competitor to be present. Pair it with roof-replacement partnerships, since spring is when roofing decisions get made and a solar-ready roof conversation is far cheaper to start than a cold solar pitch.
Summer, June to August. Peak install capacity, which means peak risk of buying leads you cannot serve. If crews are booked out six weeks, additional lead spend mostly funds slow responses. Shift budget toward referrals and existing-customer retrofits.
Autumn, September to November. Historically the tax-deadline sprint. Without 25D that urgency is gone, and pretending otherwise in ad copy is the fastest way to lose credibility with a homeowner who knows the credit expired. Sell against rate increases taking effect in the new year instead.
If your ad calendar still matches your install calendar month for month, it is roughly a quarter out of phase with your own lead times. We map spend against capacity and equipment lead times before touching creative.
The lead time problem nobody adjusts for
Panels, inverters and batteries carry four to six week lead times, and installer schedules stretch a further two to three weeks in busy regions.
Add those together and the ad that fills an install slot runs roughly two months before that slot exists. Most calendars do not account for this. They increase spend in the month they want work, which reliably produces a crush of leads for a period when crews are already committed, followed by a gap when the ads are switched off.
The practical fix is unglamorous: build the media calendar backward from crew availability, not forward from the season.
What actually changed the seasonality: storage
The most useful number in this market is not about solar at all.
A record 45% of Q1 2026 residential solar installations included battery storage. Nearly half of new customers are buying resilience alongside generation.
That matters for timing because storage demand does not follow irradiance. It follows grid events. Outages, storms, rolling blackouts and rate restructuring all cluster in seasons when traditional solar advertising goes quiet. An installer with a winter capacity gap and a storage offer has a genuinely counter-seasonal product, and it is also the part of the market that never depended on the federal credit, which is why it held up when new installs did not.
Watch out
Do not run 2026 ad copy that leans on federal tax savings. The 25D credit expired December 31, 2025, and homeowners researching solar know it. Quoting a dead incentive reads as either out of date or dishonest, and it is one of the fastest ways to lose a comparison shopper who is already skeptical.
Two mistakes the data explains
Cutting spend to zero in the slow months. The slow month is when your competitors are absent and utility bills are highest. Cutting entirely surrenders the cheapest auction of the year and leaves a pipeline gap eight weeks later, because of the lead-time lag above.
Reading a strong quarter as a strong market. Q1 2026 was backlog conversion. Installers who scaled spend against it were bidding into demand that had already been captured months earlier. Judge the market by new signed contracts, not by installs completed, since installs lag sales by a quarter or more in this trade.
The underlying point
Solar seasonality used to be a question about weather and deadlines. In 2026 it is a question about utility economics and grid reliability, and those run on a completely different clock.
Advertise into the months when a homeowner is angry at their utility, not the months when the roof looks good in a photograph. For most markets that inverts the traditional calendar, which is precisely why the traffic is cheaper there. Where that demand actually originates is covered in best lead sources for solar companies, and if you would rather build the pipeline than rent it, solar lead generation without buying leads covers the five lists worth assembling first.