Quick Answer: Hosted VoIP (Asterisk, Avaya Cloud, BT Cloud Voice) costs £5-£12/user/month and requires no infrastructure investment. Teams Phone costs £6.70/user/month (calling extra) and bundles with Microsoft 365. UCaaS suites (Five9, Avaya, NICE) cost £15-£35/user/month but include contact centre, recording, and compliance features. Total cost of ownership differs sharply by use case. Calculate TCO over 3 years to identify the right fit for each customer segment.
Total Cost of Ownership Comparison Over 36 Months
The headline price per user masks hidden costs: migration, training, integration, support, and infrastructure. This TCO model compares three platforms for a 100-user organisation over 3 years.
| Cost Category | Hosted VoIP (BT Cloud Voice) | Microsoft Teams Phone | UCaaS Suite (Five9 or Avaya) |
|---|---|---|---|
| User Licenses (100 users, 36 months) | |||
| Monthly per-user cost | £10/month (blended) | £6.70 (Teams Phone) + £8 (Microsoft 365 E3) | £25/month (blended) |
| Total licence cost (36 months) | £36,000 | £52,600 (Teams Phone £24,120 + M365 £28,480) | £90,000 |
| Infrastructure and Platform | |||
| On-premise hardware (SBC, switches) or cloud hosting | £0 (cloud-hosted by BT) | £0 (Microsoft cloud) | £0 (cloud-hosted by vendor) |
| Network bandwidth upgrades (if required) | £1,200/year (assuming upgrade needed) | £600/year (Teams lighter than legacy VoIP) | £1,800/year (UCaaS heavier traffic profile) |
| Total infrastructure (36 months) | £3,600 | £1,800 | £5,400 |
| Implementation and Integration | |||
| Migration planning and execution | £3,000-£5,000 (number porting, device setup) | £2,500-£4,000 (typically simpler, cloud-native) | £5,000-£8,000 (API integration, custom IVR) |
| Staff training and change management | £1,500 | £2,000 (Teams adoption often slower) | £3,000 (contact centre requires deeper training) |
| Third-party integrations (CRM, ERP, etc.) | £2,000 (limited native integrations) | £1,500 (extensive Microsoft ecosystem) | £4,000 (rich API for integrations) |
| Total implementation (one-time, Year 1) | £6,500-£8,500 | £6,000-£7,500 | £12,000-£15,000 |
| Ongoing Support and Professional Services | |||
| 24/7 support premium (if required, per year) | £4,000/year | £3,000/year (lighter SLA for cloud-native orgs) | £8,000/year (contact centre criticality) |
| Quarterly business reviews and optimisation | £2,000/year | £1,500/year | £3,000/year |
| Reported issues and escalations (internal cost to reseller) | £5,000/year (estimated support headcount) | £4,500/year (less complex troubleshooting) | £8,000/year (feature-rich platform) |
| Total support (36 months) | £33,000 | £27,000 | £57,000 |
| PSTN Calling and Trunking Costs | |||
| Monthly PSTN calls and trunking (estimated 2,000 minutes/month) | Included in per-user price | £0.013 per minute (wholesale) = £2,600/year | Included in per-user price |
| Total PSTN costs (36 months) | Bundled | £7,800 | Bundled |
| Feature Additions and Add-Ons | |||
| Call recording (if extra) | £2/user/month = £7,200 (36 months) | £1.50/user/month = £5,400 (36 months) | Included |
| Compliance and audit tools | £500/year = £1,500 (36 months) | £300/year = £900 (36 months) | Included |
| Total add-ons (36 months) | £8,700 | £6,300 | Included |
| TOTAL TCO (36 MONTHS) | £91,300 – £97,700 | £96,100 – £105,400 | £169,200 – £177,400 |
| Cost per user per month (all-in) | £76-£81 per user | £80-£88 per user | £141-£148 per user |
| Break-even vs Hosted VoIP (savings or premium) | Baseline | -1% (slightly cheaper or parity) | +76% premium cost |
Feature and Capability Comparison
Cost alone does not determine fit. Feature availability, compliance, and integration depth differ sharply.
| Capability | Hosted VoIP | Teams Phone | UCaaS Suite |
|---|---|---|---|
| Core voice calling | Yes. Unlimited internal, metered external (PSTN). | Yes. Unlimited internal and UK calling (with Calling Plan). | Yes. Unlimited internal and external. |
| Call recording and compliance | Add-on (£2-£3/user/month). Limited compliance reporting. | Add-on (£1.50/user/month). Integrates with M365 compliance framework. eDiscovery built-in. | Native to platform. Full HIPAA, PCI-DSS, GDPR compliance certifications included. |
| Contact centre features (IVR, queues, reporting) | Basic IVR available. Reporting limited to call logs. Not designed for contact centres. | Not included. Must add third-party CCaaS platform. | Yes. Skill-based routing, real-time analytics, quality monitoring, screen recording included. |
| Integration with CRM (Salesforce, Dynamics, Pipedrive) | Possible via webhooks and third-party middleware. 4-8 week implementation. | Native integration with Dynamics 365. Salesforce requires middleware. Slack native. | Deep API. Native to Five9, NICE, Avaya ecosystems. Salesforce/Dynamics integrations pre-built. |
| Meeting and collaboration | Separate platform (Zoom, Google Meet, etc.). | Teams meetings native. Unified presence and calling. Phone and meeting in one app. | Separate platform (Zoom, Webex, Teams, etc.). Some UCaaS suites offer meeting lite versions. |
| Mobile client | Yes. Supports iOS, Android. Often app-only calling (uses data, not PSTN when mobile). | Yes. Teams mobile app. Calling via Teams if VPN configured or Calling Plans active. | Yes. Native mobile app with full feature parity (contact centre features accessible on mobile). |
| On-premise option (hybrid) | Possible (Asterisk, Avaya Aura). Requires capex and IT resource. | Not available in UK market. Cloud-only via Microsoft. | Available for some vendors (Avaya, Cisco). Capex £50k-£200k. Reseller hosting available. |
| Multi-site and failover | Centralised cloud. No automatic failover to backup site. Manual config required. | Geographic redundancy automatic. 99.9% SLA. No reseller config needed. | Automatic geographic failover. 99.95%-99.99% SLA depending on vendor. Built for enterprise. |
| Compliance certifications (UK-specific) | Ofcom ECN compliance. GDPR compliance. Resilience (7-day criteria) varies by provider. | Ofcom ECN compliance (via calling plan provider). ISO 27001. UK data residency (EU regions have residency guarantees, but UK tenants may reside in EU). | Ofcom ECN (if applicable). ISO 27001, SOC 2 Type II. HIPAA, PCI-DSS, GDPR. UK data residency options available. |
Customer Risk Assessment Matrix
Beyond cost and features, assess risk across implementation, technology obsolescence, vendor lock-in, and support availability. This matrix guides reseller recommendations.
| Risk Factor | Hosted VoIP | Teams Phone | UCaaS Suite | Reseller Mitigation Strategy |
|---|---|---|---|---|
| Implementation timeline risk | Medium. Number porting can delay 2-4 weeks. Device config required. | Low. Cloud-native, fast provisioning. 1-2 weeks typical. | High. CRM and IVR integration adds 4-8 weeks. Feature-heavy. | Hosted VoIP: start porting early, prepare device inventory. Teams: test Calling Plan compatibility. UCaaS: scope integrations upfront, assign dedicated project manager. |
| Vendor lock-in risk | High. Proprietary platform. Switching requires data export and re-provisioning. | Medium. Microsoft ecosystem lock-in. Teams Phone portable via Direct Routing. | High. Proprietary IVR logic, call recordings, custom workflows not portable. | Hosted VoIP: sign 1-year contracts minimum to justify migration investment. Teams: position as part of M365 ecosystem. UCaaS: focus on feature ROI over platform lock-in fear. |
| Support and escalation risk | Medium. Vendor support is cloud-provider backed. Reseller skill set critical. | Low. Microsoft support is 24/7 and global. Reseller provides implementation/integration support. | Low-Medium. Vendor support is strong, but complex platform means reseller must have deep expertise. | Hosted VoIP: build internal expertise, maintain SOP runbooks. Teams: rely on Microsoft support, add value via integration and change management. UCaaS: certify support staff with vendor, establish escalation partnerships. |
| Technology roadmap and EOL risk | Medium-High. Older VoIP platforms (some Asterisk forks) deprecating. Newer platforms (BT Cloud Voice) stable. | Low. Microsoft invests heavily in Teams. No EOL in sight. Regular feature releases. | Low. Vendors (Five9, NICE, Avaya Cloud) invest in ongoing development. R&D-heavy sector. | Hosted VoIP: vet platform stability, check vendor roadmap. Teams: align with M365 strategy. UCaaS: review vendor R&D spend and market positioning. |
| Compliance and regulatory risk | Medium. Ofcom compliance depends on vendor. PSTN switch-off deadline (Jan 2027) requires migration plan. | Low. Microsoft compliance is tight. Calling Plans provider handles 999/112. PSTN switch-off no impact (cloud-native). | Low-Medium. Vendor compliance strong, but feature complexity (recording, IVR) creates audit surface area. | Hosted VoIP: ensure vendor has Ofcom ECN licence, confirm PSTN switch-off readiness. Teams: validate Calling Plans provider compliance. UCaaS: request compliance certifications upfront, document in SLA. |
| Cost escalation risk | Medium. Per-user and per-minute costs creep over time. International calling add-ons expensive. | Low. Per-user pricing stable. Metered costs (calling, add-ons) transparent. Cost visibility in M365. | Medium. Per-user cost may increase 5-8% annually. Add-on modules (analytics, recording) upsold over time. | Hosted VoIP: lock multi-year rates, set spending caps, monitor usage. Teams: encourage unlimited calling plans, bundle with M365. UCaaS: negotiate 3-year rates, document escalation caps in SLA. |
Frequently Asked Questions
Should I recommend one platform or offer all three?
Offer all three. Different customer segments have different needs. Hosted VoIP suits cost-conscious SMEs. Teams Phone suits Microsoft 365-native organisations. UCaaS suites suit contact centres and verticals requiring deep compliance. Build expertise in all three to maximise your addressable market.
What is the total cost of ownership for a 500-user organisation?
Scale the 100-user model. Fixed costs (migration, infrastructure) increase by 30-40%. Per-user costs drop 10-15% due to volume discounts. Expect £40k-£60k savings per year in support and infrastructure. Build a TCO calculator into your sales process.
Can I migrate customers from Hosted VoIP to Teams Phone without service disruption?
Yes. Plan a phased migration: preserve existing Hosted VoIP platform. Activate Teams Phone on new pilot group. Port phone numbers in phases. Decomission old platform after validation. Typical timeline: 4-6 weeks for 100 users.
What is the reseller margin difference between the three platforms?
Hosted VoIP: 25-35% margin (high wholesale cost). Teams Phone: 0-5% margin on core calling (Microsoft sets price), but 100% margin on add-on support and services. UCaaS: 20-30% margin with volume discounts. Build margin recovery via support and integration services.
How do I quantify the ROI of migrating from legacy PBX to cloud voice?
Calculate: (legacy PBX maintenance cost + PSTN line costs + hardware replacement cost) minus (cloud voice cost + migration cost) divided by (migration cost). For most organisations, cloud voice breaks even in 18-24 months.
Which platform best supports the PSTN switch-off deadline (31 Jan 2027)?
Teams Phone and modern Hosted VoIP (BT Cloud Voice, Gamma, Zen) are PSTN switch-off ready. Legacy on-premise PBX with ISDN/analogue lines is not. Audit customer PSTN usage and device dependencies now. Plan migration by Q4 2026.
Sources
Gartner UCaaS and Hosted VoIP Market Research
Cisco Collaboration and Contact Centre Solutions
Microsoft Teams Phone and Calling Plans
Cavell Consulting VoIP and Telecommunications Analysis
ISP Review UK Telecoms and VoIP News
Partner Playbook: Customer Segmentation and Platform Recommendation
| Customer Segment | Recommended Platform | Key Selling Points | Reseller Value-Add |
|---|---|---|---|
| Cost-conscious SME (10-50 users) | Hosted VoIP | Low per-user cost. Predictable monthly spend. No infrastructure investment. | Migration support. Device provisioning. 24/7 support bundle. |
| Microsoft 365 native organisation (25-200 users) | Teams Phone | Unified productivity. Teams integrated calling. Compliance via M365. | Teams Phone onboarding. Calling Plans setup. CRM integration (if using Dynamics). |
| Contact centre or growth-focused (50-500 users) | UCaaS Suite | Advanced analytics, quality monitoring, skill-based routing. Compliance certifications. | Implementation and integration. Change management training. Ongoing optimisation. |
| Legacy PBX with custom features (50-200 users) | Direct Routing (Teams Phone) or Hosted VoIP | Preserve feature set during transition. Hybrid approach. Phased migration path. | PBX-to-cloud assessment. Custom feature mapping. Migration project management. |
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