Why 2025's Low CAC Was a Trap, Not a Trend
Residential solar CAC hit a five-year low of $0.60 per watt in 2025. That looked like good news, but it was really a symptom of a different problem: the looming expiration of the Section 25D tax credit created a demand rush, and that rush let installers coast on inbound interest while cutting marketing spend. The cushion was temporary by design. It disappears the moment the deadline passes and the rush of ready-to-buy homeowners with it.
That is exactly what happened. Wood Mackenzie projects CAC spiking 40% to $0.84 per watt in 2026, as installers go back to fighting for a genuinely smaller pool of eligible buyers, without the tailwind of a looming deadline pulling demand forward for them.
What's Actually Driving the 2026 Spike
Three forces are compounding at once. First, the buyer pool itself shrank overnight when Section 25D ended for cash and loan purchases. Second, the financing mix that is replacing loan sales, lease and power purchase agreement structures, requires a different sales motion and a different buyer conversation, which raises cost per qualified conversation. Third, outsourced dealer networks, the 1099 sales-org model much of the industry runs on, are facing the largest margin compression of any acquisition channel in 2026, while companies that bring acquisition in-house are preserving more margin per watt.
The result is an acquisition environment where the vendor you buy from matters more than it did in 2025, because a lead vendor optimized purely for loan-qualified homeowners is now optimizing for a shrinking slice of the actual buyer pool.
What CAC Actually Costs, Per Completed Sale
Translated into dollars, published benchmarks put customer acquisition cost at $800 to $2,500 on a typical $25,000 residential installation, with a commonly cited target of a 3-to-1 lifetime-value-to-CAC ratio. That is why forward-thinking installers are shifting from one-time-sale economics toward customer lifetime value models, layering in battery upsells, EV chargers, roofing, and referrals to spread acquisition cost across more than a single sale.
A pay-per-sit appointment sits differently inside that math than a CAC line item does. A $300 setup plus $249 per booked, double-confirmed appointment does not scale with loan size and does not depend on whether the homeowner ends up financing in cash, a loan, or a lease, which matters more in a year where the financing mix itself is the thing driving CAC upward.
Sources
The external data in this article draws on the sources below. Figures described in the text as estimates or industry triangulations are directional and are not attributed to a single dataset.
- Wood Mackenzie, 2026 residential solar CAC outlook
- Sol-Ark, surviving the 2026 residential solar market
- IntegrateSun, solar dealer fees analysis
- Wall Street Prep, customer acquisition cost (CAC)
- bodhi.solar, why solar CAC runs high