STIR/SHAKEN and Answer Rates: What Solar and Home Services Callers Need to Know in 2025

Why Answer Rates Are Declining for Outbound Callers

Carrier-level call analytics — implemented by AT&T, Verizon, T-Mobile, and most MVNOs — score every inbound call on a combination of signals: call origination pattern, number reputation, attestation status, call frequency from a given number, and complaint history. Calls that score poorly get labeled "Spam Likely," "Scam Risk," or "Potential Spam" on the recipient's screen. Many are silently blocked before ever ringing.

For outbound-heavy industries like solar installation, HVAC service, and home improvement contracting, the problem is structural. These are businesses that dial at high volume from a small set of numbers, which is exactly the pattern that carrier analytics treat as suspicious — even when the calls are entirely legitimate. The answer is to operate on infrastructure that signals legitimacy at the technical level, and STIR/SHAKEN attestation is the primary mechanism for doing so.

What STIR/SHAKEN Actually Does

STIR/SHAKEN is a framework for cryptographically signing outbound calls with an attestation level that tells downstream carriers how confident the originating network is in the call's legitimacy:

Full Attestation (A): The originating carrier has verified the identity of the caller and has confirmed that the caller is authorized to use the calling number. Highest trust signal.

Partial Attestation (B): The originating carrier has verified the caller's identity but cannot confirm they are authorized to use that specific number. Mid-tier trust.

Gateway Attestation (C): The originating carrier can only verify that the call entered the network at a specific point — it cannot verify the caller's identity. Lowest trust. Most calls from shared or poorly-provisioned trunks receive this.

Calls traveling on UnlimCall's network receive A-attestation for US and Canadian outbound calls where the caller ID is properly provisioned to the account. This is not an automatic outcome of using any SIP trunk provider — it requires that the originating number be demonstrably linked to your account and that the origination chain meets the attestation standards.

Why Provisioned Caller IDs Matter for Attestation

The attestation level depends in part on whether the originating carrier can link your calling number to your identity. Numbers from a shared pool — where multiple customers share the same outbound number set — create an attestation problem: the carrier can verify the pool is real but cannot unambiguously link any individual call to a specific verified caller.

UnlimCall provisions caller IDs on demand, assigned to your account specifically, across 33 live markets. When your solar company's agent calls a California homeowner from a 916 number that is registered to your account, the attestation chain is clean. The carrier receiving that call sees a full-attestation signed call from a number that is provably yours. Compare that to calls originating from a shared number pool with gateway-level attestation — the difference in labeled-spam rate is measurable.

Answer Rate Impact for Solar and Home Services

Industry data from solar inside sales teams that have migrated to attested infrastructure consistently shows a 15–25% improvement in answer rates compared to unattested or gateway-attested calls from similar number pools. For a team making 500 calls per day, a 20% improvement in answer rate means 100 additional conversations per day from the same agent headcount — without adding a seat.

The compounding effect is larger. Every answered call that converts to an appointment, or a confirmation, or a renewal avoids a retry loop. Fewer retries means fewer calls per outcome, which means your agents are spending time on conversations rather than auto-dialed voicemail. Flat-rate trunking at $99/seat/month means the additional call volume from retries is cost-free, but it is still wasted time. Better answer rates reduce wasted time.

STIR/SHAKEN Is US and Canada Only

STIR/SHAKEN is defined by FCC mandate and implemented across US and Canadian carrier networks. For operations dialing into other markets — UnlimCall serves 33 countries, including active markets in Europe and Latin America — STIR/SHAKEN does not apply. Each market has its own regulatory framework for caller ID and spam labeling. UnlimCall operates under the regulatory requirements of each active market, but STIR/SHAKEN attestation is explicitly a US/CA feature.

For operations focused on US and Canadian home services markets — where the bulk of solar, HVAC, roofing, and pest control volume is concentrated — STIR/SHAKEN attestation is the relevant technical standard.

What STIR/SHAKEN Does Not Do

STIR/SHAKEN solves the authentication problem — proving that the number in the caller ID field is really being used by the entity claiming to use it. It does not:

• Guarantee calls are not labeled spam by third-party analytics overlays (Hiya, First Orion, TNS).
• Substitute for a DNC-compliant calling program.
• Shield high-frequency campaigns from reputation damage if call complaint rates are elevated.
• Apply to text messages (SMS has a separate regulatory regime).

Your compliance team's DNC scrubbing, call frequency controls, and opt-out management are the primary defenses against reputation degradation. STIR/SHAKEN attestation is a technical hygiene baseline that removes one category of filter risk. The two are complementary, not interchangeable.

*This post is informational and does not constitute legal or compliance advice. Consult legal counsel for TCPA and FCC regulatory obligations specific to your outbound calling program.*