An HVAC shop's AI phone agent lifted bookings from 55% to 71% of calls
In plain words
A 60-day trial put an AI voice agent on a small HVAC firm's line. It does proper HVAC intake, books into Google Calendar and texts the on-call tech only for true no-heat/no-cool calls.
What happened: 71% of calls now become bookings, up from 55%. Nearly half of calls came outside business hours (their own figures).
These numbers come from the builder and haven't been checked independently.
Source: reddit.com ↗
How to do it yourself
Our suggested steps. The company didn't publish theirs.
- 1
Check your phone log: how many calls did you miss last month, and when?
- 2
Write down your services, service area, rough prices and what counts as an emergency.
- 3
Set up the voice agent, connect Google Calendar and an SMS alert to your on-call tech, and paste the prompt below.
- 4
Call it 20 times yourself as different customers and fix anything odd.
- 5
Turn it on for after-hours and missed calls first; review the call log weekly.
The instructions to give the AI
Paste this into Retell AI (the free plan is fine), swap the [brackets] for your details, and test it on a few real examples.
This is one part of the setup. It won't connect to your phone, inbox or other apps on its own; the steps above cover that.
Agent instructions (prompt)
You answer for [HVAC company]. Ask: home or business, what system, what's happening, and their address. If they have no heat below [x]°F or no cooling above [y]°F, text [on-call phone] now and tell them a tech will call within 15 minutes. Otherwise book the next available slot. Never diagnose.
[Highlighted] = replace with your own details before you run it.
What you should get back: Most calls end as a booked visit; a real no-heat call triggers a text: "EMERGENCY no heat, 22 Elm Rd, call back now."
Written by Quickly and Good, inspired by this case.
More detail: tools, prices and what you'll need
The company used: Retell AI or Vapi voice agent
You could use: Voice agent + Google Calendar + SMS
- Retell AI
Phone voice agents that answer and make calls, book appointments and transfer.
Pay as you go, $0.07-$0.31/min; $10 free credit · Official site ↗
Prices from each tool's own pricing page, checked Oct 2026.
What you'll need
- ☐A phone number the agent can answer (from the voice platform or Twilio)
- ☐A voice-agent platform (e.g. Retell AI, Vapi or Synthflow)
- ☐Connection to your calendar or job system so it can actually book
- ☐A knowledge base: services, prices, hours, service area, FAQs
- ☐The agent instructions (prompt) and a call script
- ☐20+ test calls, including angry, confused and off-topic callers
- ☐Transfer to a human for emergencies and anything it is unsure about
- ☐Call-recording/AI disclosure that meets local rules
Can I do this myself?
Possible if you are comfortable wiring tools together and testing for a week or two. If not, hire a builder: most owners do.
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