I Lost £12,000 in One Winter to Missed Boiler Calls. Here's the Exact Maths.

5 AM. December 15th. Minus 4 degrees. My phone rings. I'm asleep.

Voicemail at 7 AM: "It's Pat from Didsbury. Our boiler's gone completely. Three kids under ten, no heating, no hot water. I've called four engineers and you're the only one who didn't answer."

I called back at 7:15. She'd already booked someone else. £280 callout plus a new pump. Total job value: £650. Gone. Because I was asleep.

That was the fourth one that week. And it was only Tuesday.

I'm Charlie. Heating engineer from Chorlton, Manchester. 9 years self-employed. Gas Safe registered. Boilers, central heating, underfloor, annual services, landlord certificates. I cover south Manchester — Didsbury, Chorlton, Whalley Range, Stretford, Salford Quays. And this is exactly how much money I was losing to missed calls last winter.

How many boiler calls do heating engineers actually miss?

I counted. Properly. For the whole of January before signing up to whoza.ai.

Week 1: 14 missed. Week 2: 11 missed. Week 3: 13 missed. Week 4: 9 missed.

That's 47 missed calls in one month. January 2026. The coldest January in Manchester for 8 years according to the Met Office.

Out of those 47, I worked out roughly 34 were genuine jobs. The rest were existing customers chasing invoices, suppliers, recruitment agencies, and one confused bloke who thought I was a pizza shop.

But 34 real boiler and heating enquiries? In one month? And I missed them because:

• 18 were while I was on other jobs (under floors, in lofts, in airing cupboards where you can't hear the phone)
• 12 were between 6 PM and 8 AM (evenings and mornings, when I'm off the clock)
• 4 were during my daughter's Saturday football matches (I'm not giving those up)

The worst? Saturday, January 11th, 2:37 AM. Minus 6 degrees. Family in Salford — young baby, boiler completely dead. I slept through the call. They got through to voicemail, left a message, then called the next number. My competitor charged them £380 for an emergency callout. New PCB board. Total job: £890. I would have done it for £680. They paid £210 more because I didn't answer my phone.

And here's the maths that made me sign up. I worked it out on a Sunday afternoon with a calculator and a cup of tea.

34 genuine missed calls × average job value of £350 = £11,900 in lost revenue. In one month. That's not theoretical. That's actual jobs I could have done, that went to other engineers because I didn't answer.

What happened when Katie started answering my boiler calls?

Mark the gas engineer from Glasgow put me onto whoza.ai. Said Katie was answering his calls and sending WhatsApp messages with everything he needed. I was sceptical. AI answering phones for heating emergencies? Sounds like one of those rubbish chatbots that puts you through 8 menus before hanging up.

But Mark showed me his phone. WhatsApp message from Katie:

All that from a phone call. And Katie sounded proper. Not robotic. She asked about the boiler make, the fault code, the property type, whether there were vulnerable occupants. All the questions I'd ask myself if I was answering.

I signed up for the 7-day free trial. No credit card. Thought I'd test it and cancel if it was rubbish.

Week 1 with Katie: The numbers

Monday: Katie answered 4 calls I missed. Two proper jobs. One was a landlord with 8 properties in Whalley Range needing annual service certificates. £1,600 of guaranteed annual work. I would have missed it because I was bleeding a radiator in Stretford.

Tuesday: Katie answered 3 calls. One was a 5 AM emergency — boiler failure in a care home in Salford. Six residents, no heating. £450 emergency callout. I called back at 6:30 AM and had it fixed by 8. The manager said she'd called three engineers. Only Katie answered.

Wednesday: 5 calls captured. Two were system upgrades. One was a smart thermostat installation. £340 job.

Thursday: 4 calls. One was a nightmare — Worcester Bosch combi with a failed diverter valve. Customer had already been quoted £1,200 by another engineer. I did it for £780. Katie had captured the exact model number, the fault description, and the fact the customer had been quoted already. I called back knowing exactly what parts to bring.

Friday to Sunday: 6 more calls captured. Three jobs booked. Total for the week: 22 calls answered, 11 jobs booked. Revenue from captured calls: £3,400.

Week 4: The maths

After 4 weeks with Katie, I sat down and did the same calculation.

That's not a typo. Eight thousand two hundred and seventy-five pounds. In one winter month. From calls I would have missed.

The jobs I would have definitely lost without Katie

January 18th, 11:47 PM: Boiler breakdown in a nursery in Chorlton. 34 children. No heating. £580 emergency callout. I was asleep. Katie captured it. I was there by 7 AM.

January 22nd, 6:15 AM: Pensioner in Didsbury. Boiler pressure at zero, leaking from underneath. £220 callout plus new pressure relief valve. I was having breakfast. Katie got it. I called back within 10 minutes.

January 29th, 2:22 PM: Estate agent in Salford Quays. Four rental properties need gas safety certificates by end of week. £800 of certified work. I was in a loft space with no signal. Katie answered, captured all four addresses, and the deadline.

Every single one of those would have gone to a competitor. Every one.

The honest downsides (because nothing's perfect)

I've got to be honest. It's not all perfect. Two things:

1. Katie occasionally gets the boiler model wrong if the caller doesn't know it. About 1 in 10 times, she'll put "boiler" instead of "Worcester Bosch Greenstar 30i". Not a big deal — I always confirm when I call back.
2. One customer thought Katie was a real person and tried to book a specific time. Katie explained I wasn't available and would call back, but the customer got a bit confused. Sorted it when I called back.

Neither of those cost me a single job. And both are massively outweighed by the 28 jobs I captured.

Would I go back to voicemail? Never.

I used to think voicemail was fine. "They'll leave a message and I'll call back." They don't. 85% of people who hit voicemail hang up and call the next number. That's not my stat — that's from a proper business report. And it matches exactly what I saw.

Before Katie: 47 missed calls in January, £11,900 lost revenue.

After Katie: 63 enquiries captured, 28 jobs booked, £8,400 recovered revenue.

Cost: £125/month.

If you're a heating engineer and you're still sending customers to voicemail, you're not just losing calls. You're losing boilers, certificates, service contracts, and emergency callouts to every competitor who answers their phone.

And in winter? That's £8,000+ per month walking out the door.