Cloud ERP runs on rented infrastructure, either as a vendor's shared subscription service (SaaS) or hosted in your own cloud account. On-premise ERP runs on servers you own and operate. The choice decides who is responsible for uptime, security and upgrades, how far you can customise, where data lives, and how you pay.
Most comparisons treat this as a two-way choice. In practice there are three models, and the middle one (a custom or single-tenant ERP hosted in your own cloud account) is often the best fit for companies that need control without running a server room.
What are the three ERP deployment models?
The three models are multi-tenant SaaS ERP, single-tenant hosted ERP (packaged or custom) in a cloud account, and on-premise ERP. They differ mainly in who controls the software, the infrastructure and the upgrade timetable.
| Multi-tenant SaaS ERP | Hosted single-tenant or custom ERP | On-premise ERP | |
|---|---|---|---|
| Who runs the infrastructure | The vendor | A cloud provider, managed by you or your partner | You |
| Who controls upgrades | The vendor's schedule | You decide when | You decide when |
| Customisation | Within the vendor's extension framework | Full, within the code base | Full, within the product or code base |
| Data location | The vendor's available regions | The region you choose in your cloud account | Your own premises |
| Cost pattern | Subscription, usually per user | Development or licence plus cloud and support costs | Licence or development plus hardware, facilities and staff |
| Scaling | Handled by the vendor | You size and scale the resources | You buy and install hardware |
| Typical fit | Standard processes, fast start, small IT team | Distinctive processes, data residency needs, growing user base | Strict isolation rules, existing data centre, limited connectivity |
If your processes do not fit a package and you want the system hosted where you choose, our custom ERP software page explains how we deliver it. For moving an existing system, see the cloud ERP migration guide.
Who is responsible for uptime and security in cloud ERP?
Responsibility is shared, and the split depends on the model. The cloud provider secures its infrastructure; you remain responsible for how your system and data are configured and used.
AWS describes this as a shared responsibility model: the provider handles "security of the cloud" (facilities, hardware, the infrastructure that runs its services), while customers are responsible for "security in the cloud" (their data, applications, operating system and configuration choices). Other major providers publish similar models. In practice:
- With SaaS ERP, the vendor runs the application as well, so your remaining duties are user access, roles, data quality, integrations and your own configuration.
- With hosted custom ERP, you or your partner run the application layer: patching, backups, monitoring, access control and incident response. Agree in writing who does what. Our security and data protection page sets out how we approach this.
- With on-premise ERP, you own all of it, including power, hardware failure and physical security.
Ask any vendor for its availability commitment, how it measures it, what is excluded (such as planned maintenance), and what happens to your data if you leave.
How does data residency affect the choice?
Data residency rules can narrow the options before cost is even considered. Check where each option stores and processes data, including backups and support access, and confirm the rules that apply to you with your own legal advisers.
- In the UK, the ICO's guidance on international transfers (checked October 2026) says UK GDPR restricts transfers of personal data outside the UK unless they are covered by adequacy regulations, appropriate safeguards such as the International Data Transfer Agreement, or a limited exception. A cloud ERP that stores or lets support staff access data abroad needs to fit one of those routes.
- In the UAE, the federal Personal Data Protection Law (Federal Decree-Law No. 45 of 2021), described on the official u.ae portal, covers personal data processing, while free zones such as DIFC and ADGM have their own data protection laws, and some sectors have their own rules. Companies often prefer an ERP hosted in a UAE cloud region for this reason.
- In the US, there is no single federal rule for ERP data. Sector rules and state privacy laws apply depending on what you process, so the main question is usually contractual: where data is stored and who can access it.
A hosted single-tenant or custom ERP lets you choose the region. A SaaS ERP limits you to the regions the vendor offers, which may or may not include yours.
How do costs compare between cloud and on-premise ERP?
Cloud shifts cost from one-off purchases to recurring payments; on-premise does the opposite. Neither is cheaper by default. It depends on users, growth, hardware refresh cycles and the staff you need.
| Cost line | SaaS ERP | Hosted custom ERP | On-premise ERP |
|---|---|---|---|
| Software | Subscription | Development (one-off) plus changes | Licence or development (one-off) plus maintenance |
| Infrastructure | Included | Cloud resources, billed monthly | Servers, storage, networking, refresh every few years |
| Facilities | None | None | Power, cooling, space, physical security |
| Staff | Administrator and key users | Support partner or in-house DevOps | Infrastructure and database administrators |
| Disaster recovery | Vendor's design | Backups and recovery you configure | Secondary site or backup service you run |
Put the figures into a five-year model before deciding. The ERP total cost of ownership guide gives a template.
How does the deployment model limit customisation?
Multi-tenant SaaS ERP limits customisation the most, because every customer runs the same code. You can usually configure fields, workflows and reports and build extensions through the vendor's framework, but you cannot change the core, and the vendor's release schedule decides when your extensions must be retested.
Single-tenant hosted and on-premise systems let you change anything, including the data model. That freedom is useful when a core process does not fit a package, and costly when it is used without discipline. The ERP customisation vs configuration guide explains where to draw the line.
| Question | SaaS ERP | Hosted custom ERP | On-premise ERP |
|---|---|---|---|
| Can we change the data model? | Within the extension framework | Yes | Yes |
| Can we delay an upgrade? | Usually not for long | Yes | Yes |
| Can we run a specific integration inside our network? | Through connectors or middleware | Yes, with network design | Yes |
| Who retests customisations after upgrades? | You or your partner, on the vendor's timetable | Your development team | Your team or partner |
What should you ask a cloud ERP vendor or hosting partner?
- In which regions are production data, backups and logs stored?
- From which countries can support staff access our data?
- What availability does the contract commit to, how is it measured, and what is excluded?
- How often are backups taken, how long are they kept, and when was a restore last tested?
- How are security incidents reported to us, and how quickly?
- How do we export all our data, in what format, if we leave?
- Who applies security patches, and how quickly after release?
Decision checklist: which model fits?
- Do our core processes fit the package without major customisation? If yes, SaaS is a strong candidate.
- Do we need full control of when upgrades happen? If yes, hosted or on-premise.
- Do data residency rules require a specific country or region? Check whether the SaaS vendor offers it.
- Do we have staff, or a partner, to run patching, backups and monitoring?
- Are users expected to grow quickly, making per-user pricing expensive?
- Do we have sites with poor connectivity that need local operation?
- Do we need deep integration with systems that only run on our own network?
- Is there an existing data centre investment we must use?
When is cloud ERP not the right approach?
Cloud ERP is a poor fit where sites operate with unreliable internet and cannot stop work during an outage, where a regulator or contract requires data to stay on premises, or where deep integration with on-site machines and old systems would add more complexity than it removes. In those cases on-premise, or a hybrid with local services that sync to a cloud system, may be better.
Equally, on-premise is rarely the right choice for a growing business without an IT team. The work of patching, backing up and securing servers falls on someone, and it is easy to underestimate. If your current on-premise system is ageing, legacy software modernisation explains the routes for moving it, from rehosting as it is to rebuilding it module by module.
How to start
Write down your must-have modules, your data residency constraints, your upgrade and uptime expectations, and who will run the system day to day. Add the sites and users that must keep working during an internet outage, the systems the ERP must reach inside your own network, and any customer or regulator contracts that say where data may be stored. These answers usually decide the deployment model before cost does. A software requirements brief is a good format for this.
Then discuss the project with us. Timeline Digital builds 2 to 3 key modules as a free pilot before the full project starts, hosted in the environment you plan to use, so you can test performance, access and data location before committing.