AI receptionist for HVAC. No heat, no AC, no voicemail.

First sub-20-degree night in November. Phones in every HVAC shop in the metro start ringing at 6pm and don't stop until midnight. Your dispatcher picks up three. Voicemail picks up the other twelve. The homeowner in a 52-degree house tries your shop, gets voicemail, tries the next one, gets voicemail, tries the third, picks the one that picks up. That's the whole game.

This is a field note on what an AI receptionist for HVAC contractors actually has to do, triage no-heat and no-AC emergencies, handle the seasonal spike without dropping calls, quote the dispatch fee, offer the maintenance plan, the boring stuff that decides whether the rig books jobs or just looks busy. Same engine as our after-hours answering service, tuned to an HVAC dispatch protocol.

§ 01The seasonal spike.

Three patterns. Every HVAC shop. Every season.

• First cold snap. The first night the outdoor temp drops below 20°F, no-heat calls spike 4–6x normal. The shop that picks up every call books a week's worth of work in one evening. The shop that doesn't loses customers who'll never call back next season.
• First heat wave. Same pattern, July. The first 95°F day with a heat advisory. Compressor calls, refrigerant calls, "AC won't turn on" calls. Three days of triage decide the summer's revenue.
• Shoulder-season tune-ups. Spring and fall maintenance. Lower urgency, higher volume of routine scheduling. Most shops let these calls sit until someone has time to call back. The customers don't wait, they let it slide until something breaks in the next season, and call whoever shows up in the Google map pack.

§ 02What the spike actually costs.

Conservative floor. Two-truck residential HVAC shop.

Assumptions, written down

• 240 inbound calls per month, normal week
• Spike weeks (4 per year): 800+ calls / week each
• Of spike calls, ~40% go to voicemail in a typical shop
• Average HVAC service ticket: $400–$1,200 (diagnostic + repair)
• System replacement ticket: $6,000–$18,000 (often surfaced from no-heat / no-AC diagnostics)

That puts the spike-weeks leak at roughly 300+ unanswered calls per year, of which ~30% are bookable jobs — $36,000–$80,000 in deferred revenue, before any system-replacement opportunities. The rig that plugs this is $2,000, fixed, once. The math is not subtle.

You can't hire a part-time dispatcher for two weeks a year. You can build a rig that picks up every call for two weeks a year and goes back to being quiet the other fifty. From a shop-owner interview, March 2026

§ 03The triage protocol.

"AI receptionist" demos answer the phone in a friendly voice and take a message. That's not enough for HVAC. The protocol has four branches and a seasonal layer.

Branch 1 · Life-safety emergency

Gas smell. Carbon monoxide alarm sounding. These do not go to the HVAC dispatcher first. The rig routes to the utility or the fire department, with first-aid instructions to the homeowner (leave the house, open windows, don't flip switches). Then it logs the customer for an HVAC follow-up call once they're safe.

Branch 2 · Comfort emergency

No heat in winter. No AC in heat-advisory weather. Indoor unit leaking water on the floor. Ice on the outdoor unit. The rig pages the on-call tech in seconds with the customer's address, system type if known, and 30-second summary. Customer gets a holding SMS and a confirmed ETA window.

Branch 3 · Urgent service

Reduced cooling, intermittent heat, weird noise, thermostat issue. Booked into the next available slot inside the dispatch window. ServiceTitan or Housecall Pro writes the job.

Branch 4 · Routine

Maintenance, tune-up, filter changes, install consults, IAQ questions. Booked into the next routine slot. Maintenance-plan offer surfaces here.

§ 04The rig, in five pieces.

Same shape we ship for plumbing, dental, real estate, and after-hours. Five pieces. The spike-handling capability is what HVAC needs that the others don't.

1. The front number. CallRail tracking number or your main shop line, forwarded or routed direct to the AI. Twilio for unlimited concurrent calls, no busy signal during the spike.
2. The voice + SMS stack. Voice for callers who dial. SMS auto-response within 60 seconds for missed or overflow calls. The rig speaks HVAC English (condenser, evaporator, refrigerant, thermostat, drain pan, ductwork), not generic call-center.
3. The FSM integration. ServiceTitan, Housecall Pro, Jobber, FieldEdge, or ServiceBridge. The rig reads dispatcher availability and writes new jobs with the right business unit (residential vs. commercial), job type, priority code, and customer record.
4. The on-call escalation. Direct ring to the on-call tech's phone for triaged emergencies. Pushover, Telegram, or carrier SMS with tap-to-call. Rotation logic for multi-tech on-call.
5. The morning runbook. 7am email summarizing every call the rig handled overnight: emergencies dispatched, urgent jobs booked, routine bookings, maintenance-plan signups, out-of-scope referrals. The dispatcher walks in knowing what's already on the board.

// rough shape of the HVAC dispatch webhook
on inbound.call →
  classify(intent, priority, season) →
    LIFE-SAFETY    → route utility/fire, log HVAC follow-up
    COMFORT-EMERG  → page on-call tech + first-aid SMS + ETA
    URGENT         → book next slot, FSM write, confirm SMS
    ROUTINE        → book + maintenance-plan offer, FSM write
  log to morning_runbook

§ 05ServiceTitan, Housecall Pro, FieldEdge.

Same FSM landscape as plumbing, most HVAC shops run one of four systems. We ship against whatever's already in place.

• ServiceTitan. The most common platform in mid-sized and franchise HVAC. Real API. Cleanest integration, read dispatch board, write jobs with the right business unit and priority code.
• Housecall Pro. Common in single-truck and small residential. Public API, simpler data model.
• FieldEdge. Common in shops with both HVAC and plumbing service lines. Older platform, usually needs a server-side adapter. Add 2–3 days to the build.
• Jobber. Common for shops growing past Housecall Pro but not yet at ServiceTitan scale. Public API, well-documented.

§ 06The maintenance plan offer.

The maintenance plan is the highest-margin product an HVAC shop sells. The AI receptionist surfaces it at the right moment, a routine tune-up call, a customer with an aging system, a no-heat call where the diagnostic surfaces an unmaintained furnace. Within rules you set, the rig:

• Quotes the published plan price. Whatever your tier structure is, bronze, silver, gold. Same number, every call.
• Names the included visits. Spring AC tune-up, fall furnace inspection, filter delivery, priority dispatch. The rig knows your plan's deliverables.
• Signs the customer up if they accept. Membership writes back to the FSM with the right SKU. Recurring billing handled inside your existing system.
• Does not push. If the customer declines, the rig moves on. Aggressive pitching loses calls.

§ 07Takeaway, in one line.

The first cold snap and the first heat wave are coming. The shop with an AI receptionist for HVAC picks up every spike-week call, triages it, dispatches the emergencies, books the routine work, and offers the maintenance plan at the right moment. The shop without one writes the same post-season report about why spike-week revenue underperformed. The rig is two weeks of work. The math pays back inside the first spike.

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If you run an HVAC shop and you've read this far, the next step is the same as everywhere else on the site. Fifteen minutes. One question: where do the spike-week calls go?