Power Automate vs Custom Workflow Automation: An Honest Comparison

If your business runs on Microsoft 365, Power Automate is the obvious starting point for automation — some of it is already included in licences you pay for, and your IT provider probably knows it. For a large share of everyday office workflows, it is genuinely the right answer, and we say that as a company that builds custom workflow automation.

But Power Automate's sweet spot has edges: licensing tiers that surprise you, connector gaps outside the Microsoft ecosystem, throughput limits, and a low-code model that gets awkward exactly when workflows get valuable. This guide maps those edges honestly, so you can decide with your eyes open.

Power Automate's biggest advantage is that it is already there. Most Microsoft 365 business licences include cloud flows with standard connectors — Outlook, SharePoint, Teams, Excel, Planner — which covers a surprising amount of office admin: approval routing, file organisation, notifications, simple data entry between Microsoft apps. It sits inside your existing tenant, inherits your security model, and gives IT admins genuine governance tooling (data loss prevention policies, environment controls, flow analytics).

The licensing picture is where SMEs get caught out. The moment a flow touches a premiumconnector — SQL Server, HTTP calls to arbitrary APIs, Salesforce, DocuSign, custom connectors and many more — every user of that flow needs a premium licence. As of mid-2026, the Premium per-user plan runs around £12–15 per user per month, and unattended desktop automation (RPA bots that run without a person at the keyboard) is licensed separately per bot at a much higher price point. Each licence tier also carries daily action limits, so a high-frequency flow can hit throttling that is awkward to diagnose and costly to lift.

Pros: included with licences you already own for basic use; native Microsoft 365 integration; familiar to IT partners; solid admin and compliance tooling inside the tenant; huge template library.

Cons:premium connector licensing multiplies across users; daily action limits throttle busy flows; connectors for non-Microsoft systems are often shallow or missing; desktop (RPA) flows are fragile — they mimic clicks on screens, so a vendor updating their UI can silently break them, whereas API-based automation talks to the system directly and survives interface changes; the expression language stops being “low-code” quickly; and flows are typically owned by the individual who built them, so a leaver can strand business-critical automation. Governance tooling is good, but in practice many SMEs accumulate dozens of undocumented flows that nobody fully understands — sprawl is a process problem the tool does not solve for you.

Custom workflow automation is built for your specific process, integrating systems through their APIs — including Microsoft 365 itself via Microsoft Graph — rather than through a connector catalogue. That removes the three ceilings SMEs most often hit with Power Automate: it connects to anything with an API (your industry-specific CRM, a legacy system, a supplier portal), it has no per-user or per-run licensing, and it can embed AI judgement steps — reading unstructured emails, extracting data from documents, classifying and routing requests — with validation rules and human review where accuracy matters.

The honest trade-offs: there is a real upfront cost (for most SME workflows, a few thousand pounds depending on scope), delivery takes weeks rather than an afternoon, and you depend on a partner to build and maintain it rather than tweaking flows yourself. For a simple approval chain in Teams, that overhead is plainly not worth it — Power Automate wins that comparison every time.

Custom tends to win when: the workflow crosses system boundaries Power Automate serves poorly; volumes would trip action limits or force premium licences across a team; steps need judgement rather than rules; the process is business-critical enough that screen-scraping RPA fragility is unacceptable; or you want the automation owned by the business — documented, transferable, and not tied to one employee's account. If you are weighing up several candidate processes, our free automation priority scorer ranks them by frequency, hours consumed, and error cost, so you can see which workflow justifies which approach before spending anything.

• Choose Power Automate if your workflow lives inside Microsoft 365, standard connectors cover it, volumes sit comfortably under the action limits, and your IT partner can own the flows. It is effectively free at this tier and entirely fit for purpose.
• Stay with Power Automate (Premium) if you need a handful of premium connectors for a small number of users and the workflow logic remains rule-based — the per-user cost is modest at small scale.
• Choose custom automation if the workflow spans non-Microsoft systems, premium licensing would multiply across a team, volumes are high, steps need AI judgement or document understanding, or you have been burned by fragile desktop RPA flows and need something that survives vendor UI changes.
• Mix them if sensible: many of our clients keep simple internal flows in Power Automate and use a custom build only for the one cross-system, high-value process it cannot handle well.

If you are unsure which side your process falls on, a 30-minute review is normally enough to tell — and if Power Automate is the right tool for you, we will say exactly that.