The verdict in three sentences
A maintenance retainer for a B2B website in London costs, in 2026, between 180 and 950 EUR/month, depending on the SLA and the volume of dev hours included. Below 180 EUR/month you only get monitored hosting, not real maintenance; above 950 EUR you move into full managed support. An unmaintained site is not free: it costs 0 EUR right up until the day a breach costs you 15,000.
What a maintenance retainer actually covers
A serious retainer is not "we check if the site is up." It stacks several layers, each with an avoided cost attached. Here is the typical breakdown of a 2026 contract for a B2B brochure or corporate site (WordPress, Next.js or headless CMS).
| Included service | Frequency | Avoided cost if absent |
|---|---|---|
| Security updates (CMS, plugins, dependencies) | Monthly | 3,000-15,000 EUR (breach remediation) |
| Automated backups + restore testing | Daily | 2,000-8,000 EUR (data loss) |
| 24/7 uptime monitoring + alerts | Continuous | 500-4,000 EUR/day of commercial downtime |
| Bug fixes and micro-changes | 2-8 h/month | 600-900 EUR/day on time-and-materials |
| Monthly report (perf, security, traffic) | Monthly | Flying blind |
| SSL renewal + GDPR check | Continuous | Browser blacklist, ICO fine |
The variables that move the price are the number of dev hours included and the guaranteed recovery time (RTO). A 250 EUR/month contract typically includes 2 hours; a 700 EUR/month contract includes 6 to 8, with intervention within 4 business hours.
Time-and-materials vs retainer: the real trade-off
Many SMEs think they save by paying "on demand." In practice, time-and-materials costs more as soon as you need more than two interventions a year, and above all it leaves you with no safety net between tickets.
| Criterion | On demand (T&M) | Retainer |
|---|---|---|
| Rate | 600-900 EUR/day | 180-950 EUR/month |
| Response time | Not guaranteed (agency schedule) | SLA 4-24 h by tier |
| Preventive updates | None (you call after the incident) | Included, scheduled |
| Backups | Your responsibility | Included + tested |
| Typical annual cost | 1,800-5,400 EUR (3-6 jobs) | 2,160-11,400 EUR (full cover) |
| Residual risk | High (site exposed between calls) | Low |
The T&M trap: an emergency Friday-night intervention after a defacement is billed at premium rate, and you also pay the audit hours to figure out what happened. A retainer turns a volatile risk into a predictable budget line.
Mini case study
Sarah, COO of a 40-person industrial SME in London, refused the retainer "to save 300 EUR/month." In March 2026, an un-updated plugin opens a vulnerability: the site is defaced, flagged by Google as a spam site, and offline for 5 days. Remediation invoice: 6,200 EUR (cleanup, restore, de-indexing, audit). Add the lost leads over a week (the form generated ~8 requests/week at ~1,500 EUR potential margin each). A 300 EUR/month retainer (3,600 EUR/year) would have prevented the incident. ROI of the retainer on this single event: it pays for itself in under two months.
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FAQ
What is the minimum credible retainer budget in 2026?
Expect at least 180-280 EUR/month for a brochure site. Below that, you only pay for passive monitoring with no dev hours, which does not cover real fixes.
Does the retainer include hosting?
Not always. Some contracts bundle it (full managed support), others bill it separately (30-90 EUR/month). Check this: an "all-in" contract at 500 EUR is often better than 300 EUR plus hosting plus SSL as add-ons.
How many dev hours are actually used per month?
On average 1 to 3 hours for a stable site. Busy months (page rebuild, campaign) reach 6-8 hours. A good contract lets you roll unused hours over a quarter.
What happens if I exceed the included hours?
Extra hours are billed at the contract's T&M rate, usually 90-130 EUR/h, cheaper than one-off T&M. That is the retainer's main financial advantage.
Can I cancel easily?
Serious contracts are no-commitment or quarterly, with one month's notice. Avoid 24-month lock-ins on a brochure-site retainer.
Let's scope your project. Tell us your stack (WordPress, Next.js, headless CMS), business criticality and target SLA; we will price a retainer between 180 and 950 EUR/month. 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.
