The One-Paragraph Frame
Vapi is the developer's platform: maximum flexibility, modular architecture, bring your own everything. Best when you need custom logic that no off-the-shelf solution handles.
Retell is the production platform: best latency, strongest compliance posture, fastest path from zero to a working agent. Best when you want results without becoming a voice AI infrastructure engineer.
Bland is the scale platform: built for high-volume outbound, proprietary speech models, enterprise data governance. Best for contact-center-level campaigns, not typical residential inbound.
For most home service AI builds HVAC, plumbing, roofing, electrical, locksmith the choice is between Vapi and Retell, depending on how much technical complexity you want to own.
Why Latency Is the Only Metric That Actually Matters
Before the breakdown: latency is the deciding factor in voice AI UX. Natural human conversation turn-taking happens at 200–300ms. Below 700ms, conversations feel natural. Above 900ms, callers disengage and hang up.
This isn't a nice-to-have it's the difference between a voice agent that books jobs and one that creates confused, frustrated callers who call your competitor next.
Measured across production deployments:
Retell AI: 580–620ms average response time
Vapi (optimized stack): 500–600ms with the right STT/LLM/TTS provider pairings
Bland AI: ~800ms average
Both Vapi and Retell can hit sub-650ms in production. Bland's proprietary stack runs consistently at 800ms acceptable for outbound campaigns where callers are expecting a call, challenging for inbound where a homeowner calls about an emergency plumbing issue and needs a human-feeling response.
Vapi AI: Maximum Control, Maximum Complexity
What It Is
Vapi is a developer-first voice AI orchestration layer. You bring your own speech-to-text provider (Deepgram, AssemblyAI), your own LLM (GPT-4o, Claude), your own text-to-speech (ElevenLabs, Cartesia), and your own telephony (Twilio, Telnyx). Vapi handles the orchestration between them — the real-time audio streaming, the turn management, the function calling that lets your agent write to your CRM mid-call.
Where Vapi Wins for Trades Builds
Custom dispatch logic. When you need a voice agent that checks real-time technician availability, routes emergency vs. scheduled calls differently, and passes specific data fields into your CRM at the end of every call, Vapi's function-calling architecture handles this cleanly. You write the logic; Vapi executes it in real time.
LLM flexibility. You choose GPT-4o, Claude 3.5 Sonnet, Llama whatever model performs best for your specific use case. We've found GPT-4o best for real-time voice response quality, Claude better for structured data extraction in post-call workflows.
Cost control at scale. Vapi's platform fee is $0.05/minute. Your actual per-minute cost depends on which STT/LLM/TTS providers you choose — a typical optimized stack runs $0.11–0.15/minute all-in. At high call volumes (10,000+ minutes/month), this is cheaper than a flat-subscription product.
No vendor lock-in. If ElevenLabs releases a better voice model next month, you swap it. If a better STT provider cuts latency, you switch without rebuilding the agent.
Where Vapi Falls Short
Setup friction. Building a production-ready Vapi voice agent from scratch takes 40–100+ hours for an experienced developer. This is not a "set it up this weekend" tool for an HVAC owner. The latency optimization alone finding the right provider combination, testing under concurrent call load takes significant time.
HIPAA complexity. HIPAA compliance on Vapi requires a $1,000/month add-on AND requires you to get separate BAAs from each provider in your stack (your STT provider, your LLM provider, your TTS provider). For healthcare-adjacent trades like medical equipment service, this is a real administrative burden.
Ongoing maintenance. When one of your providers has an outage or changes their API, your stack breaks. With Vapi, you own the maintenance.
Pricing
Platform fee: $0.05/minute (passed through at cost)
Full stack (STT + LLM + TTS + telephony): ~$0.11–0.15/minute
HIPAA compliance: $1,000/month add-on
60-day call data retention: $1,000/month add-on
10 concurrent lines by default ($10/line/month for additional)
AI Savvy verdict: Our primary build layer for custom AI voice workflows where the client needs logic that managed platforms can't handle. We don't recommend this for contractors trying to build it themselves.
Retell AI: Production-Ready From Day One
What It Is
Retell is a production-grade voice AI platform with a no-code agent builder, a developer API, and enterprise-grade compliance baked in from the start. Unlike Vapi's modular approach, Retell handles the infrastructure layer for you, you configure the agent, set up your knowledge base, define call workflows, and deploy.
Where Retell Wins for Trades Builds
Fastest path to production. Retell's drag-and-drop agent builder gets you from zero to a working inbound voice agent in hours, not weeks. You don't need to choose STT providers or benchmark latency configurations. The platform is pre-optimized.
Best latency in the managed-platform category. Retell averages 580–620ms competitive with an optimized Vapi stack. ElevenLabs v3 voice integration produces voice quality that's genuinely difficult to distinguish from human on a phone call.
HIPAA + SOC 2 Type II as standard. Self-service BAA portal on all paid plans, no enterprise contract, no $1,000/month add-on. For any trades business handling sensitive customer data or operating in regulated environments, this matters.
Post-call analytics. Retell tracks outcomes (was a job booked?), sentiment, transcripts, and conversation analysis natively. You can see which call scripts perform better and which intents your agent fails on. This feedback loop is how you improve conversion over time.
CRM integrations. Native HubSpot and GoHighLevel integrations log call summaries and update contact records automatically. For the typical AI Savvy deployment, Vapi or Retell writing to a GHL contact record, Retell's native GHL integration is cleaner.
SIP trunking support. Retell connects to any telephony provider (Twilio, Vonage, Telnyx, Avaya, or your own carrier) via SIP trunk. You keep your existing numbers and carrier relationships.
Where Retell Falls Short
Less flexibility than Vapi for complex logic. If you need a voice agent to handle dynamic pricing lookups, real-time inventory checks, or complex multi-step conditional routing, you'll hit the edges of Retell's workflow builder faster than Vapi's function-calling system.
Provider lock-in. You're trusting Retell's infrastructure choices. When they have an outage, you have an outage. For most contractors, this is an acceptable tradeoff for the setup and maintenance savings.
Pricing
Typically $0.07–0.15/minute depending on features
SOC 2 + HIPAA included on paid plans (self-service BAA)
No separate charges for concurrent lines at most tiers
At 10,000 calls/month averaging 4 minutes: ~$2,800/month vs $4,899/month on Bland's Scale plan
AI Savvy verdict: Best managed platform for inbound-heavy residential trades. When a client needs an AI receptionist live in 5 days, Retell is how we do it. The GHL integration makes it the right choice for shops already running GoHighLevel.
Bland AI: Scale and Enterprise Control
What It Is
Bland runs its own proprietary speech models and infrastructure rather than routing through OpenAI or Google. Built for high-volume outbound calling, think 50,000+ calls per month for insurance verification, appointment reminders, or outbound lead follow-up campaigns.
Where Bland Wins
Proprietary model infrastructure. At 5,000+ concurrent calls, Bland's dedicated infrastructure maintains consistent performance where shared-provider platforms see latency spikes. This matters for agency-scale outbound campaigns, not for a 5-truck HVAC shop.
Data governance. Because Bland runs its own models, your call data never touches OpenAI or Google's infrastructure. For enterprises with strict data residency requirements, this is a compliance advantage.
Outbound campaign tooling. Bland's "Pathways" builder handles multi-agent handoff during calls, a feature Retell and Vapi don't replicate as cleanly for complex outbound script trees.
Where Bland Falls Short for Contractors
~800ms latency. This is noticeable on inbound emergency calls. When a homeowner calls about a burst pipe, 800ms feels like a stutter. For outbound reminders where the caller expects to hear AI, it's acceptable.
Cost structure. The Start plan puts per-minute rates at $0.14/min. The Build plan ($299/month) at $0.12/min. Scale ($499/month) at $0.11/min. Voice cloning adds $200–$300/month. Transfer fees apply unless you bring your own Twilio.
Not designed for residential inbound. Bland's UX and tooling are oriented toward enterprise outbound. The setup complexity exceeds what's needed for a typical contractor inbound line.
AI Savvy verdict: We don't use Bland for standard contractor deployments. We use it for outbound appointment campaigns at agency scale 500+ calls per day, multi-step dialers, outreach sequences. Not the right tool for an HVAC shop answering inbound calls.
The Recommendation by Use Case
HVAC inbound calls, after-hours coverage, and job booking: → Retell. Native GHL integration, fast setup, strong latency, HIPAA included.
Custom dispatch routing, conditional CRM logic, complex multi-step inbound: → Vapi. Accept the setup complexity in exchange for the flexibility.
Outbound appointment reminders at 500+ calls/day: → Bland. The volume and data governance justify the cost.
Owner-operator who wants something running by Friday without a developer: → Neither of the above. Look at GoHighLevel's native AI Employee ($97/month) or Workiz Genius Answering for a done-for-you product. The raw platforms above require building.
The Cost Reality
Per-minute pricing sounds cheap until you model it against volume:
5-truck HVAC shop: ~300 calls/month, avg 4 minutes
Total minutes: ~1,200/month
Retell at $0.10/min: $120/month
Vapi optimized stack at $0.13/min: $156/month
Human receptionist (part-time): $1,200–$2,000/month
The AI voice layer costs ~10% of a part-time human receptionist and operates 24/7. The ROI argument is immediate and doesn't require a spreadsheet.
Frequently Asked Questions
What's the difference between Vapi and Retell for home service businesses? Vapi gives you full control over every component of your voice stack in exchange for significant setup complexity. Retell gives you a production-ready platform with a no-code builder, native GHL integration, and HIPAA compliance included in exchange for less flexibility. For most contractor deployments, Retell is faster and simpler. Vapi is better when you need custom logic.
How much does an AI voice agent cost for a 5-truck HVAC shop? Expect $100–$200/month in platform costs for a standard inbound setup on Retell or Vapi. Add Twilio telephony costs (~$1/number/month + $0.008/minute for calls) and you're at $150 $300/month total. Compare to $1,200–$2,000/month for a part-time human receptionist.
Can these AI voice agents book jobs directly into Jobber or ServiceTitan? Yes, via function calls during the live conversation. The voice agent checks tech availability in your calendar, creates the job record, and texts the customer a confirmation all during the same call. This requires custom development with Vapi or configuration work with Retell.
Do callers know they're talking to AI? With ElevenLabs v3 voices via Retell or Vapi, most callers on phone lines don't identify the agent as AI, particularly on a noisy mobile call. For callers who ask directly, the agent should be transparent.
Bottom Line
The AI voice layer is where most trades businesses are leaving the most money on the table. The technology is real, it's affordable, and contractors who deploy it first in their market win leads their competitors don't even know they're losing.
Retell for production inbound. Vapi for custom logic. Bland for outbound scale. If you're not sure which path your operation needs, we'll tell you in 30 minutes.
Book a Free Operations Audit → theaisavvy.com/contact
AI Savvy deploys Vapi and Retell for HVAC, roofing, plumbing, locksmith, and electrical businesses across the US. All platform assessments are based on production deployments, not product demos.