The verdict in three sentences
For a survey of 12,000 households run by 80 enumerators in areas with no network, a custom offline PWA costs 7 to 17 million FCFA (about EUR 10,700 to 25,900) in 2026 when built in Central Africa. KoboToolbox, which is free, is enough for a simple questionnaire but shows its limits as soon as the donor requires real-time quality control, complex consistency rules and dedicated dashboards. The realistic timeline is 10 to 14 weeks, to be planned before enumerator recruitment and training.
KoboToolbox, ODK or a custom app: the comparison
The choice is not made on price alone. An NGO or research firm reporting to an international donor (World Bank, UNICEF, AFD, European Union) is judged on the quality of the data delivered, the rejection rate of questionnaires and its ability to prove each interview actually took place.
| Criterion | KoboToolbox | Self-hosted ODK Central | Custom PWA |
|---|---|---|---|
| Software cost | 0 FCFA (humanitarian server) | 0 FCFA + server 30,000 to 80,000 FCFA/month | 7 to 17 million FCFA |
| Offline operation | Yes | Yes | Yes, designed for 30 days without network |
| Questionnaire logic | XLSForm, good | XLSForm, good | Unlimited, coded business rules |
| Real-time quality control | Limited, export then analyse | Limited | Automatic alerts per enumerator |
| Geotagged photos | Yes | Yes | Yes, compressed to 150 KB |
| Donor dashboard | Basic | To be built | Included, custom indicators |
| Quota and cluster management | Manual | Manual | Assignment by area and progress tracking |
KoboToolbox remains the right choice for a one-off survey of fewer than 2,000 households. Beyond that, or for a survey repeated over several rounds, a custom app cuts the heaviest hidden cost: return trips to the field to fix inconsistent questionnaires.
Detailed budget for an offline PWA
| Item | 2026 range (FCFA) | Scope |
|---|---|---|
| Scoping and questionnaire modelling | 800,000 to 1,500,000 | Household, individual and dwelling modules, skips and filters |
| Offline field PWA | 2,500,000 to 6,000,000 | Encrypted local storage, forms, photos, GPS |
| Delayed synchronisation | 1,000,000 to 2,500,000 | Batch upload, resume after drop, conflict handling |
| Supervisor back office and quality control | 1,500,000 to 4,000,000 | Duration, out-of-area GPS and outlier alerts |
| Donor dashboard and exports | 700,000 to 2,000,000 | Progress, indicators, Stata, SPSS, CSV exports |
| Field testing and training | 500,000 to 1,000,000 | Pilot on 100 households, supervisor training |
| Total | 7,000,000 to 17,000,000 | Excluding tablets and hosting |
Add hosting (40,000 to 120,000 FCFA a month) and entry-level Android tablets at 90,000 to 140,000 FCFA each in Brazzaville. A PWA runs on modest devices, as long as you plan for at least 3 GB of RAM and 32 GB of storage for photos.
Technical choices that make the difference in the field
Three decisions drive success. First, encrypted local storage: household data is sensitive and a lost tablet must expose nothing. Second, small-batch synchronisation: on an intermittent 2G connection in remote districts, uploading 300 questionnaires at once fails, while batches of 20 go through. Third, automatic server-side checks: an interview shorter than 12 minutes, a GPS point more than 2 km from the assigned cluster, or an age inconsistent with the declared relationship trigger an alert to the supervisor the same day.
Mini case study
Mr Mabiala, project lead at a research firm in Brazzaville, runs a 12,000-household survey for an international donor. In his previous survey on simple forms, 9% of questionnaires were rejected at final review, i.e. 1,080 interviews to redo. Each interview costs about 6,500 FCFA (allowance, transport, supervision), and a field return doubles that cost: about 14 million FCFA in rework.
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With a custom app at 11 million FCFA, he targets a 3% rejection rate, i.e. 360 redos and about 4.7 million FCFA. Estimated saving: 9.3 million FCFA from the first round, and the tool can be reused for the two follow-up rounds in the contract. A 2026 order of magnitude, to recompute with actual field costs.
FAQ
How many days can a tablet stay offline?
A well-built PWA keeps hundreds of questionnaires locally: 30 days of collection, about 150 households per enumerator, takes less than 1 GB including photos.
Can an existing XLSForm questionnaire be reused?
Yes, the logic of a Kobo or ODK XLSForm is the basis for scoping and cuts modelling time by 20 to 30%.
Where should data be hosted to meet donor requirements?
Donors usually ask for secure hosting with daily backups and access control. A server in Europe or Africa costs 40,000 to 120,000 FCFA a month depending on photo volume.
How is the project paid?
Usually in three instalments: 40% at kick-off, 40% at pilot delivery, 20% after collection. Payment by bank transfer, Wave or Orange Money.
What lead time before data collection starts?
10 to 14 weeks, including a 2-week pilot on 100 households. Start development at least 3 months before enumerator training.
Let's scope your project. Send us your questionnaire and sampling plan: we price the field app, quality control and donor dashboard (indicative budget of 7 to 17 million FCFA, 10 to 14 week timeline). 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.
