AI phone assistant for a car workshop: the actual maths

One recovered booking pays three months of assistant

The maths is shorter than vendors make it. The cheapest plan costs 69 euros a month, and a service costs between 100 and 600 euros according to the German motoring club ADAC. At a job value of 250 euros the assistant has to recover 0.28 bookings a month to pay for itself, so one booking every three and a half months. That is not a close call.

It gets close somewhere else. A recovered call is extra revenue only if the ramp would otherwise have stood empty. Vendor pages do not do that sum, and it decides the case.

The calculation needs only two sourced numbers

A monthly price and a job value. Both are public; the rest are assumptions every workshop already knows. The inputs used here, as read on 22 September 2026:

• Workshop labour rate: 202 euros an hour for mechanical, electrical and body work in 2024, from the German insurers' association GDV using DEKRA data, VAT included.
• Service job value: 100 to 600 euros according to the ADAC, oils and brake fluid excluded.
• Cheap assistant: Placetel AI Grow, 69 euros with 750 minutes.
• Mid assistant: fonio Solo, 119 euros with 1,000 minutes, so 0.12 euros a minute.
• Assumption, not sourced: 3.5 minutes per call and 21 working days a month.

The monthly price equals 20 minutes of workshop labour

That conversion ends the price debate. 69 euros divided by the 202 euro hourly rate is 20.5 minutes of workshop labour; fonio's 119 euros is 35.3 minutes. A service taking an hour and a half of labour, by contrast, bills 303 euros in labour alone, parts not counted.

The minute budget binds sooner than the price does. At 3.5 minutes a call, 750 included minutes cover 214 calls a month, a little over ten a day; 1,000 minutes cover 286 calls, close to fourteen a day. A shop with two service desks in tyre season runs past that, and extra minutes then cost 15 euros per 100 minutes on fonio's Solo plan.

Calls are lost in the evening, not at lunchtime

The gap sits outside opening hours. LDB Gruppe, a phone service specialising in car dealerships, reports from its July 2026 analysis that 28 per cent of unhandled calls came in after 6 pm or at the weekend, and that 90 per cent of customers had phoned their dealership at some point in the previous year.

That points to the cheapest setup. Put the assistant on your main number in the evening, at night and at weekends first, not during the day. A person still takes the daytime calls, the minute budget stays nearly untouched, and the effect is the one the figure above describes. After four weeks the assistant's call list shows how many conversations actually landed there.

The conversion rate is the shakiest number

This is where the case is decided, not on the plan. An assistant answers the call, but not every answered call becomes a booking, and not every booking would have been lost without it. The list below gives the number of recovered bookings per month at which each plan pays for itself, calculated with python3 as monthly price divided by job value:

• Placetel Grow, 69 euros: 0.69 bookings at a 100 euro job value, 0.28 at 250 euros, 0.12 at 600 euros.
• Telfo Basis, 79 euros: 0.79 bookings at 100 euros, 0.32 at 250 euros, 0.13 at 600 euros.
• fonio Solo, 119 euros: 1.19 bookings at 100 euros, 0.48 at 250 euros, 0.20 at 600 euros.
• Strictly counted, if only 30 per cent of recovered bookings are genuinely extra: 0.92 bookings a month at 69 euros and a 250 euro job value, 1.59 at 119 euros.
• Even in the strict version the threshold is one to two bookings a month. That is the real finding here.

When it stops paying off

At full capacity the maths flips. If your workshop is booked out three weeks ahead, a recovered call moves revenue rather than creating it. The only benefit left is a calmer front desk, and 69 euros for that is still defensible while 359 euros is not.

Two further cases argue against it. First, the one-man shop with regulars who ring twice anyway: there the assistant replaces a callback, not a job. Second, the workshop with no digital diary, because an assistant that delivers bookings only by email builds a second list next to the first. Two lists are exactly one list too many.

Three things the assistant must not say

The line runs at every binding commitment. A cost estimate, a repair approval and a delivery date for a part are statements the business is held to, not intake of a request. The assistant takes the registration, the request and the callback number; the service desk calls back.

One duty has applied since the summer. Article 50 of the EU AI Act requires callers to be told at the first interaction that they are speaking to an AI system, and under Article 113 that has applied since 2 August 2026. One sentence at the start of the call satisfies it. What else the regulation asks of smaller firms is in our piece on the AI literacy obligation under Article 4.

What I would do in your place

Yes, when three things line up: more than ten calls a day, a waiting time for a slot under two weeks, and a digital diary the assistant can write into. Then start on the 69 euro plan, outside opening hours only, and measure for four weeks how many bookings came out of it.

No, if you are booked out more than three weeks ahead, or if you would first have to digitise your diary. In both cases the assistant buys a problem that sits elsewhere. Our piece on AI cost per case shows how to price such workflows per case rather than per month.

Common questions

• What does such an assistant sound like? Our free AI phone demo plays in the browser without signing up.
• Can it reach the workshop software? Only through an interface the vendor names explicitly. Without one it stays at email or a callback list.
• What happens to customer data from the call? A registration plate and a name are personal data. Our piece on removing customer data before a prompt and its free tool show what to strip first.
• Is an annual contract worth it? Not before those four weeks of measurement. Until then you do not know the number that matters.

The next step

For one week, count the calls that hit voicemail after closing time and at weekends, and note how many of those callers rang back. The difference is your own input for the table above. If it is more than two calls a week, set the cheapest plan up for those fringe hours; if you would rather have the setup and the handover into your workshop software done with you, the route runs through our services.