Build the calculation from your enquiry funnel and job contribution, not a generic missed-call revenue claim. Use separate monthly assumptions where seasonality matters.
A proposed planning model is:
Additional completed jobs = the lower of available incremental job capacity and eligible enquiries × improvement in completed-job conversion
Monthly net benefit = additional completed jobs × contribution per job + realised cost reductions − all incremental operating costs
First-year net benefit = sum of the 12 monthly net benefits − one-off implementation costs
Allow negative conversion differences in the evaluation. If automation worsens outcomes, the model must show the lost contribution.
What belongs in the cost model?
Include setup, data preparation, integration, training, licences, number rental, forwarding, AI and carrier minutes, messages, workflow runs, monitoring, human answering, internal supervision, remediation, changes and exit assistance. Show the applicable VAT treatment and any foreign-currency exposure explicitly; an unspecified charge remains unknown, not zero.
Billing details can change the calculation. Retell’s published pricing FAQ says its AI fee stops after transfer while telephony fees continue, and that silence or hold time remains billable. Ask how the actual proposed stack treats these events rather than assuming one provider’s rules apply to all suppliers. (retellai.com)
What does a worked example look like?
Illustration only: every input below is hypothetical, not a market benchmark, supplier quote or forecast.
| Input | Illustrative assumption |
|---|---|
| Eligible enquiries per month | 80 |
| Current completed-job conversion, including existing callbacks | 25% |
| Proposed completed-job conversion | 40% |
| Additional jobs implied before capacity limits | 12 |
| Available incremental job capacity | 10 |
| Contribution per additional completed job | £150 |
| Total incremental monthly operating cost, including supervision and rework | £1,100 |
| One-off implementation cost | £3,600 |
The capacity limit reduces the credited gain to 10 jobs, producing £1,500 contribution and £400 monthly net benefit. If those assumptions held for all 12 months, first-year net benefit would be £1,200 after setup.
Recurring break-even requires eight additional completed jobs per month at these inputs. Recovering setup within one year requires approximately 9.33 jobs per month, or at least 112 additional jobs across the year; a steady whole-job monthly target would be ten.
If the conversion improvement were only five percentage points, the model would produce four additional jobs and a £500 monthly loss before setup, assuming the same operating-cost envelope. This is why the pilot must test the conversion uplift rather than simply confirm that calls are being answered.
Do not extrapolate a peak-season result across a full year without a separate seasonal model. Compare the proposal’s incremental result with a priced native-software or human-answering alternative.
Sources cited on this page
- retellai.com ↗www.retellai.com