A formula you can actually fill in
Start with calls that used to end in voicemail or a hang-up. Multiply the ones you now answer by the share that become a real job, visit, or appointment. Multiply that by the value of one of those outcomes. Subtract the monthly cost of the agent.
You do not need a perfect conversion rate on day one. Use a conservative guess, then replace it with your own numbers after a month. If one saved job pays for the service, the rest of the month is the argument.
Metrics that matter more than talk time
Answered calls. Messages with a callback number. Transfers that reached a person. Calls that asked for something you do not offer, which you can stop paying a human to hear. Time from the call to the follow-up.
An AI receptionist makes those counts visible because every call can leave a summary. The summary is only useful if the facts in it came from the caller and from your notes, not from a guess.