How should a business choose between custom software and SaaS?
Buy and configure a mature SaaS product when it can complete the company's frequent and high-risk core workflows and its APIs, data export, permissions, and three-year cost are acceptable. Choose partial or full custom development only when an uncovered difference directly affects revenue, efficiency, compliance, or product advantage, or when hardware and legacy integration impose hard constraints.
Coverage is not a feature count. A CRM with hundreds of functions may fail if it cannot express the business's customer-ownership or settlement rule. A different button position, report colour, or minor field does not justify rebuilding mature software. Wavesteam converts each difference into measurable loss or opportunity before recommending a route.
| Route | Condition | Advantage | Hidden cost / constraint | Recommendation |
|---|---|---|---|---|
| SaaS plus configuration | Common workflow, urgent launch, acceptable APIs and export | Fast, mature, continuously improved | Recurring account/use fees, limited customization and exit | Assess first |
| SaaS plus custom extension/integration | Mostly standard with a few critical differences or connections | Retains mature features and limits custom scope | Cross-system permissions, consistency, vendor upgrades | Preferred modernization path for many businesses |
| Full custom | Distinct core workflow or deep hardware, algorithm, and multi-system coupling with sustained investment | Control of roadmap, data, and experience | Highest initial and continuing maintenance | Use when difference creates sufficient value |
First, test candidates with real workflows rather than a wish list. Include frequent work, rare high-risk events, exceptions, and staff transition—for example customer creation, non-standard quotation, approval, refund, cross-department handover, and export. Frontline users execute tasks in the trial and record completion, manual workarounds, re-entry, permission gaps, and weekly time. “Customizable” in a sales demonstration must exist in the chosen plan and admin console.
Second, verify non-negotiable constraints: data region and sector rules, SSO and organization access, API/webhook scope, historical import and complete export, backup, audit, availability, deletion, and contract exit. NIST SP 800-145 defines SaaS as use of a provider-operated application with limited control of underlying infrastructure. That limited control enables low operations cost but must be acceptable.
Third, compare three-year total cost rather than first-year subscription and development quotes. SaaS includes implementation, users, modules, API, storage, messaging, training, migration, and price-change exposure. Custom includes discovery, engineering, tests, cloud, security, stores and third parties, operations, upgrades, and handover. Include training and opportunity cost of changing existing work. Model low, medium, and high user/volume scenarios with currency, tax, and price date.
Evidence for full custom can include device protocols and site control as the product itself; unique order, pricing, distribution, or dispatch logic; several legacy systems needing a common identity and source of truth; external customer experience as a competitive asset; or data/models requiring independent evolution. Wavesteam's public BMS battery management and smart energy swap cases show device-and-workflow directions, but every new protocol and difference still needs validation.
Warning signs are standard commerce, attendance, collaboration, or service requirements; an unproven process expected to be fixed by software; budget for a one-time build but no maintenance; no owner or acceptance samples; or customization solely to avoid annual fees. Source ownership does not remove upgrades, security, and operations cost.
The evaluation deliverable lists candidates, coverage and gaps, configuration versus development, integrations, three-year cost, major risks, pilot measures, and exit. If SaaS wins, Wavesteam can limit work to selection, migration, or integration. If a key difference requires custom work, the first release becomes one acceptable loop. The service process and project budget guide explain the related engagement and costing approach.