The verdict in three sentences
A B2B site delivered without a maintenance contract starts losing value in the first quarter: unpatched flaws, missing backups, frozen content. In 2026, the rule of thumb puts ongoing maintenance at 15-20 % of the build cost per year, meaning EUR 100-300/month for a brochure site and EUR 300-800/month for an institutional one. The real trade-off is not the monthly price but the scope and the SLA: what is covered, and how fast you get fixed.
Monthly retainer: what maintenance covers
A solid maintenance plan is not empty insurance: it combines security, backups, fixes and an allowance of small changes. Here are the tiers seen in the market in 2026 (order of magnitude).
| Plan | Price/month | Scope included | Change hours | Restore SLA |
|---|---|---|---|---|
| Essential (brochure) | EUR 100-200 | Security updates, backups, uptime monitoring | 1 h | 72 business h |
| Pro (brochure +) | EUR 250-450 | + light SEO, monthly reporting, fixes | 3 h | 48 h |
| Business (institutional) | EUR 500-800 | + supervision, CMS updates, tests, staging | 5-8 h | 24 h |
| Custom (multi-site) | EUR 900+ | + on-call, recovery plan, annual audit | 10 h+ | 4-8 h |
Unused change hours are rarely carried beyond one month: negotiate a quarterly rollover if your activity is seasonal.
Retainer vs time-and-materials: when to switch
A retainer suits predictable, recurring needs. As soon as you chain projects (new section, CRM integration, funnel rebuild), a day-rate engagement becomes clearer.
| Criterion | Maintenance retainer | Time & materials (per day) |
|---|---|---|
| 2026 rate | EUR 100-800/month | EUR 500-750/day |
| Best for | Keeping the lights on | Heavy changes |
| Budget predictability | High | Medium |
| Responsiveness | Per SLA | To be scheduled |
| Under-use risk | Yes | No |
| Tracking | Monthly reporting | Report per mission |
Many SMEs combine both: an Essential retainer for peace of mind, plus ad-hoc days for projects.
Mini case study
Claire, CFO of an industrial SME in Lyon, paid EUR 42,000 for her institutional site. Applying the 15-20 % rule places annual maintenance between EUR 6,300 and EUR 8,400, i.e. EUR 525-700/month. She picks a Business plan at EUR 600/month (EUR 7,200/year) with a 24 h SLA and 6 change hours included. Over the year she saves the equivalent of 2 day-rate days (EUR 1,400) by absorbing small requests into the retainer, and avoids a security incident whose average remediation cost exceeds EUR 4,000.
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FAQ
Is maintenance really mandatory?
Nothing legally requires it, but an out-of-date CMS is the number-one cause of B2B site hacks. Post-incident remediation often costs 3-5 times a year of an Essential plan.
What if I exceed the included hours?
Extra hours bill at EUR 80-120 in 2026, or at the day rate for large jobs. A good provider warns you before you go over.
Can I host elsewhere and only buy maintenance?
Yes, but maintenance is smoother when hosting is supervised by the same provider. Otherwise, demand full access and a clear split of responsibilities in the contract.
What contract length is reasonable?
A 12-month term is standard and lets the provider amortise onboarding. Check the reversibility clause: free recovery of code, backups and access at term end.
How does this compare with London rates?
As a 2026 benchmark, London retainers run GBP 150-900/month for equivalent scopes, often with a stricter SLA billed as an add-on.
Let's scope your project. Tell us the site type (brochure or institutional), its build cost and the target SLA, and we will size the right maintenance plan. 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.