Odoo vs ERPNext for a UK small business: the real costs nobody tells you about (2026)

When a UK small business outgrows spreadsheets and paper, the conversation usually lands on two open-source ERP platforms: Odoo and ERPNext. Both are capable. Both have large communities. Both promise to replace the chaos of disconnected tools with a single system.

But "open-source" doesn't mean "free to run", and the sticker price on the website rarely tells the full story. After evaluating both platforms in detail for a recent client project — a 15-person field service company — we want to share what we found, because the differences only become clear once you dig past the feature lists and into the practical reality of hosting, support, customisation and long-term cost.

The licensing split that changes everything

ERPNext is straightforward: every module is included, there are no per-user fees, and the entire codebase is available under the GPL licence. Whether you have 5 users or 50, the software cost doesn't change.

Odoo works differently. It comes in two editions:

• Odoo Community is genuinely free and open-source, but it's missing features most businesses need — full accounting (with automated bank reconciliation), the no-code customisation tool (Odoo Studio), native mobile apps, and advanced portal functionality. If you need any of these, Community won't cut it.
• Odoo Enterprise includes everything, but charges per user per month — roughly £20–24 per user on the Standard plan. At 15 users, that's £300–360 per month in licence fees alone, before you've paid for hosting or support. Over three years, that's £10,800–12,960 just for the right to use the software.

For a small business watching every pound, that per-user cost adds up fast — and it scales in the wrong direction. Every new hire, every office user who needs access, adds another monthly charge.

The hosting problem most people discover too late

This is where the comparison gets uncomfortable for Odoo.

If your business needs any custom functionality — and most do, because no two businesses work exactly the same way — you need custom backend modules. Custom forms, custom workflows, integrations with your accounting software or industry-specific tools.

Odoo offers three hosting options:

• Odoo Online (SaaS) is the cheapest and easiest. Odoo manages everything. But here's the catch: you cannot install custom backend modules on Odoo Online. At all. If you need custom functionality, this option is immediately off the table.
• Odoo.sh is Odoo's own platform-as-a-service. It does allow custom modules. But you're sharing infrastructure with other customers on the shared tier (starting at roughly £145/month on top of your licence fees), and dedicated resources start at around £665/month. You get no root access to the server, and Odoo controls the upgrade schedule — which matters more than you'd think when you have custom code.
• Self-hosted gives you full control but means you're responsible for everything: server provisioning, security patches, database maintenance, backups, monitoring. Either you have in-house Linux admin skills, or you're paying someone to manage it.

ERPNext on dedicated infrastructure (a Hetzner CCX server, for example) costs roughly £37–74 per month at the prices in force since Hetzner's June 2026 increase — for dedicated CPU and RAM, full root access, and no restrictions on what you can install or modify. Hetzner's ARM tier brings comparable capacity down to around £9–18 a month if your stack runs on ARM64. Against Odoo.sh, the infrastructure gap is still roughly two to nine times — and wider on ARM.

The support model nobody explains upfront

Odoo Enterprise includes support from Odoo SA — but it only covers bug fixes and security patches for their own core code. That's it.

For everything else — configuration changes, custom module maintenance, workflow adjustments, user training, troubleshooting — Odoo directs you to their certified partner network. UK-based Odoo partners typically charge £80–120 per hour, with minimum retainers around £500 per month for roughly 5 hours of support.

And here's the detail that catches people out: server administration is usually not included in the partner retainer. If you're self-hosting Odoo, the partner handles the application layer (how Odoo works), but the server layer (keeping it running, patched, backed up) is either your problem or a separate cost.

So for any issue with your system, you're potentially dealing with three separate parties: Odoo SA for bugs in their core code, your implementation partner for configuration and custom modules, and your hosting provider for server problems. When something breaks and it's not immediately clear whose responsibility it is, you're the one caught in the middle.

With a self-hosted ERPNext setup managed by a single provider, you get one relationship, one invoice, and one phone number to call. The provider handles the server, the application, the custom modules, the backups and the support. When something goes wrong, there's nobody to point fingers at. Full disclosure: that single-provider model is exactly what we offer, so weigh our conclusion accordingly — it's also why we've shown the numbers, so you can check them yourself.

The upgrade risk with custom modules

This one doesn't show up in any pricing comparison, but it's real.

On Odoo.sh, Odoo pushes updates on their schedule. If you have custom modules, those updates can break your custom code without warning. Every customisation you add increases the risk that the next Odoo update will cause problems. Your partner then needs to fix the breakage, which costs time and money — and you're paying for it.

With a self-hosted ERPNext instance, you control when upgrades happen. You test the new version against your custom modules in a staging environment first. If something breaks, you fix it before it touches production. If an upgrade isn't worth the risk right now, you wait. That control is worth more than it sounds.

What about the other options?

Odoo and ERPNext aren't the only choices. Here's why the others usually don't fit a small business in this position:

• Microsoft Dynamics 365 is powerful but expensive — per-user licensing starts at £50–60/month for basic modules, and implementation from a Microsoft partner typically runs £30,000–100,000+ for a comparable scope. It's built for mid-market and enterprise, and the cost reflects that.
• SAP Business One is similar — strong software, but implementation costs of £50,000+ and ongoing maintenance fees that are disproportionate for a 15-person company.
• Zoho One offers a broad suite at roughly £30–40/user/month, but the ERP and project management modules are less mature than ERPNext's, and deep customisation requires their proprietary scripting language (Deluge) rather than standard Python.
• HubSpot is excellent for CRM and marketing but doesn't have the operational depth for job management, timesheets, invoicing and field service workflows. You'd end up bolting together multiple systems.
• Xero, QuickBooks, FreeAgent, Sage — these are accounting tools, not ERP platforms. They're essential for what they do (statutory accounts, HMRC, VAT), but they don't manage jobs, schedules, timesheets or field operations. In practice, you keep your accounting software and add an operational platform alongside it.

What does each option actually cost per month?

For a 15-person business needing custom modules, here's what the monthly numbers look like once you add everything up.

ERPNext, self-hosted, managed by a single provider

One monthly subscription covering hosting on dedicated infrastructure, backups, monitoring, security updates, custom module maintenance, user provisioning, and phone/email support. No separate licence fees. No per-user charges. Contractor and field-worker access typically included at no extra cost.

Odoo Enterprise, self-hosted with partner support

• Odoo licence (15 users): ~£330/month.
• Hosting (VPS): ~£50–80/month.
• Server management: ~£50–150/month.
• Partner support retainer: ~£500+/month.
• Total: ~£930–1,060+/month, across 3–4 separate invoices from separate vendors.

Odoo Enterprise on Odoo.sh

• Odoo licence: ~£330/month.
• Odoo.sh hosting (shared tier): ~£145/month.
• Partner support retainer: ~£500+/month.
• Total: ~£975+/month — and that's shared infrastructure; dedicated resources add another £500+/month.

Implementation costs are comparable — both platforms need configuration, customisation, data migration and training. The difference is in the ongoing cost structure, and in the operational overhead of managing multiple vendor relationships versus one.

So which should you choose?

If your business is straightforward — standard CRM, standard invoicing, no custom integrations, no field-service complexity — and you have budget for per-user licensing, Odoo Enterprise on Odoo Online is a perfectly good choice. It's polished, well-supported, and you don't need to think about servers.

If your business needs custom modules, industry-specific workflows, integration with third-party systems (your accounting software, your design tools, your scheduling), and you want to control your costs as you grow — ERPNext self-hosted is the stronger choice. No per-user fees means your cost doesn't scale with headcount. Full customisation freedom means you're never blocked by platform restrictions. And a single managed-service provider means one relationship instead of three.

The right answer depends on your specific situation. But whatever you choose, make sure you understand the full cost — not just the licence fee on the website, but the hosting, the support, the customisation constraints, and what happens when you need to change something six months after go-live.

Frequently asked questions

Is ERPNext really free?

The software is — every module, unlimited users, GPL-licensed. What you pay for is running it well: hosting, backups, security updates, customisation and support, either in-house or through a managed provider. There is no per-user licence fee at any team size.

Can you install custom modules on Odoo Online?

No. Odoo Online (the SaaS edition) does not allow custom backend modules at all. If you need custom functionality you must use Odoo.sh or self-host, both of which change the cost picture significantly.

What does Odoo Enterprise cost for 15 users in the UK?

Roughly £300–360/month in licence fees on the Standard plan, before hosting and support. A realistic all-in monthly figure with partner support is £930–1,060+ self-hosted, or £975+ on Odoo.sh's shared tier.

Do we still need Xero or QuickBooks alongside an ERP?

Usually, yes. Accounting tools handle statutory accounts, VAT and HMRC well, and most small businesses keep them. The ERP runs operations — quotes, jobs, stock, invoicing — and connects to the accounting package rather than replacing it.

Weighing up an ERP for your own business? Book a free 30-minute discovery call — we'll look at how your business actually runs and tell you honestly which route fits, including the ones we don't sell.