The verdict in three sentences
For an HVAC maintenance company with 35 technicians, paper job sheets delay invoicing by 10 to 20 days and keep an administrator busy retyping. A custom offline app with photos, signature and PDF reports costs €25,000 to €45,000 with an Irish agency (2026 ballpark) and takes 12 to 16 weeks. Against FSM software at €35 to €70 per technician a month, custom makes sense when your maintenance contracts, service routines and ERP do not fit the standard mould.
What the app must do in the field
An HVAC engineer works in plant rooms, basements, risers and on rooftops, where signal is often zero. An app that needs a connection to save a photo or a signature will be abandoned within two weeks. Offline mode with sync is not an option, it is the foundation of the project.
| Module | Field function | Share of budget (estimate) | Build time |
|---|---|---|---|
| Scheduling and work orders | Day's route, address, asset history | 15 % | 2 weeks |
| Offline mode | Local storage, sync queue, conflict handling | 20 to 25 % | 3 weeks |
| Service routines | Checklists per asset type: heat pump, boiler, AHU, chiller | 15 % | 2 weeks |
| Photos and parts | Annotated photos, parts used, refrigerant readings | 10 to 15 % | 1.5 weeks |
| Signature and report | On-screen customer signature, PDF report emailed automatically | 10 % | 1.5 weeks |
| ERP and invoicing connector | Hours and parts pushed to Sage, Xero or the trade ERP | 15 % | 2 weeks |
| Service desk back office | Dispatch, live tracking, contract dashboard | 10 % | 2 weeks |
Compliance adds weight: under the EU F-gas Regulation, refrigerant quantities added and recovered must be recorded for equipment that contains them. The app can prefill these records and produce the required logs at each relevant visit.
Off-the-shelf FSM or custom app
FSM platforms such as Simpro, Commusoft, BigChange or Jobber are solid for standard needs. The maths change at 35 technicians with complex maintenance contracts.
| Option | Upfront cost | Annual cost for 35 technicians | 3-year cost | Limit |
|---|---|---|---|---|
| Paper sheets and retyping | €0 | about €60,000 of admin time | about €180,000 | Invoice delay, lost sheets |
| Entry-level FSM | €1,000 to €3,000 | €14,700 (€35 per technician a month) | €45,000 to €47,000 | Partial offline, rigid checklists |
| Premium FSM | €5,000 to €15,000 | €29,400 (€70 per technician a month) | €93,000 to €103,000 | Cost grows with headcount |
| Dublin agency, custom build | €25,000 to €45,000 | 15 to 20 % of build for maintenance | €36,000 to €72,000 | 12 to 16 weeks |
| Kolonell, complex application | 7,000,000 to 15,000,000+ FCFA (10,670 to 22,870+ EUR) | maintenance 120,000 FCFA a month (183 EUR) | see quote | Field workshop with 3 to 5 technicians |
Agency and SaaS figures are 2026 ballparks. The tipping point is often around 25 technicians: below that, an off-the-shelf FSM usually remains cheaper.
Getting technicians to adopt it
The main risk is not technical, it is the team rejecting the tool. Three rules reduce it. Involve 3 to 5 technicians from the mock-up stage to validate the number of taps per job, with a target under 15. Use large buttons that work with gloves and a dark mode readable in a plant room. Roll out in waves of 8 to 10 technicians, with a champion per team for two weeks.
On hardware, a PWA runs on the Android phones you already supply, with no app store involved. Budget €250 to €400 per rugged device if you renew the fleet.
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Ciarán, service manager of an HVAC maintenance company in Dublin, runs 35 technicians completing about 2,940 jobs a month (35 x 4 a day x 21 days), invoiced at €280 on average.
- Retyping job sheets: 3 minutes per sheet x 2,940 = 147 hours a month x €34 = €59,976 a year.
- Cash flow: invoicing 15 days earlier frees €823,200 x 15 / 30 = €411,600 of working capital, worth €20,580 a year at a 5 % financing rate.
- Total annual gain: €80,556.
With an app costing €40,000 from a local agency, payback comes in 40,000 / 80,556 = 0.50 years, or about 6 months. On Kolonell's complex application grid, payback is shorter still, to be confirmed on the exact scope.
FAQ
Does a PWA really work without signal?
Yes, a well-built PWA stores work orders, photos and signatures on the device and syncs when the connection returns. Conflicts, such as two engineers on the same asset, should be tested on at least 200 pilot jobs.
How long to equip all 35 technicians?
Allow 12 to 16 weeks of development, then 3 to 4 weeks of rollout in waves. The first technicians can pilot the tool from week 10.
Can we import our asset history?
Yes, import from the ERP or spreadsheets is planned at scoping, usually 1 to 2 weeks depending on data quality. A base of 3,000 assets migrates without difficulty.
Can the customer get the report on the spot?
Yes, the signed PDF report is emailed within a minute of syncing. That sharply reduces invoice disputes, often from 2 to 3 % to under 1 %.
Let's scope your project. Tell us your asset types, your ERP and your number of technicians, and we will scope an offline app deliverable in 12 to 16 weeks. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
