What does a phone system cost when you build it on open source?
If you are comparing an Asterisk or FreePBX build against a per-user hosted phone plan, the short answer is that the PBX software is usually free to license, so the total depends on how many users and sites you have, how many trunks and numbers you need, how your 911 design is handled, whether you run a contact center, and who does the implementation and support. The software line is rarely the largest one. The larger items are servers or cloud hosting, carrier charges for SIP trunks and numbers, handsets, any commercial modules you choose to add, and the engineering time to design, port, test and support the system.
This page does not publish a price list, and DeployOpen does not estimate prices for its own work. A DeployOpen quote follows from a written scope that names your sites, user counts, trunk plan, 911 requirements, queues and integrations, and the support model you want. Every carrier rate, number fee, handset price, hosting charge and commercial module price must come from the vendor or carrier quote and from your own environment. Ask each provider to separate one-time charges from recurring charges, and ask what changes when your user count, call volume or number of locations grows.
When you build the comparison, put both options on the same basis: a multi-year view that lists every recurring line (hosting, trunks, numbers, support, module renewals) and every one-time line (implementation, porting, testing, handsets, training). Then ask the hosted vendor to show the per-user fee, the features that are extra, the 911 and location features included, and the carrier minutes and number charges that sit outside the seat price. Compare the two totals against the same user and site counts, and flag any gap that depends on a feature you have not yet confirmed.
Which cost components you pay for in each option
This table compares who pays for each telephony cost component when you build in-house, hire an implementation partner to deploy Asterisk or FreePBX, or buy a commercial hosted phone plan. Read each row as a cost category, then check which party carries it and whether it is one-time or recurring. Most of the long-term difference comes from recurring rows such as trunks, support and administration.
| Cost component | In-house build | Implementation partner | Commercial SaaS |
|---|---|---|---|
| Servers or cloud hosting | Your team pays for hardware or cloud instances, redundancy and backups, recurring | Partner scopes the sizing and you pay the hosting bill directly, recurring | Provider includes hosting in the per-user fee, recurring |
| SIP trunks and numbers | You contract with carriers for channels and DIDs, recurring per channel and number | Same carrier contracts, usually held by you, so you keep control of porting and capacity | Usually bundled into the plan, though international, emergency and overage charges may apply |
| Handsets and softphone licenses | You buy desk phones and any paid softphone or client licenses, one-time plus replacement | Partner specifies and procures devices, you pay the purchase and any licensing | Handsets may be leased or bought through the provider, often with per-seat recurring fees |
| Commercial modules and vendor support | You pay for any commercial add-ons and support contracts you choose, recurring | Partner may recommend add-ons and resell or pass through their cost, recurring | Included in the subscription, with feature tiers that control what you can use |
| Implementation and number porting | Your staff plan, configure and port numbers, with internal time as the main cost | You pay a fixed-scope project fee for design, build, testing and cutover, one-time | Provider or reseller handles setup, often lower upfront effort but fewer custom changes |
| 911 and location services | You pay for emergency routing and dispatchable location services from carriers or vendors, plus testing time, recurring and one-time | Partner designs and tests the configuration, and you pay carrier or location service fees | Provider typically supplies emergency calling, but you must confirm location handling for remote and non-fixed users |
| Ongoing administration | Your staff handles changes, patching, upgrades and user moves, recurring internal cost | You pay for a support retainer if you want updates and after-hours help, recurring | Provider runs the platform, while your admins handle users, routing and reporting |
| Training | Your team pays for internal training time and vendor courses, one-time and as staff change | Partner includes handover and documentation in scope, with extra sessions billed separately | Provider offers onboarding and help content, usually included with the plan |
Which phone system costs are one-time and which recur
Most of the money in an open-source phone system falls into two buckets. The first is one-time spend: server or hosting setup, implementation, number porting, testing and documentation. These are paid once, usually against a written scope, and they are the costs that determine whether the system is ready for production. The second is recurring spend: SIP trunk charges, DID numbers, hosting, support contracts, security patching, licensed commercial modules and the internal staff hours needed to administer the system. Those costs continue for as long as the phones are in service, so a quote that shows only the first bucket understates the real annual cost.
Before you compare offers, ask each bidder to split its quote into these two columns and to name who is paid for each line. Confirm whether trunk and number charges are billed by your carrier or passed through by the implementer, whether any PBX add-on needs an annual license, and whether the support model covers patching of the Asterisk and FreePBX stack or only the initial build. Ask how many months of hosting and carrier usage the one-time estimate assumes, and what happens to port-out and number costs if you change carriers later.
A fixed-scope implementation is priced once, against deliverables agreed in writing before work starts. Ongoing support, upgrades, security patching and monitoring are not part of that price. They belong in a separate retainer, which should state response expectations, upgrade cadence and what triggers additional work. When you review that retainer, check whether it includes dial plan changes after cutover, 911 location updates when sites or floors change, and testing of major releases before they reach production. Those recurring tasks are where unplanned cost tends to appear if they are left out of the agreement.
What moves your phone system cost up or down
Phone system cost rarely scales in a straight line with headcount. Six drivers decide whether a build stays affordable or grows with every site, queue and compliance obligation, and each one should appear in the written scope before a quote is compared.
User and seat count
Per-seat costs come from handsets, softphone licenses, and any commercial modules priced by extension. Server capacity usually matters less than people expect at moderate scale, so the main cost question is how many endpoints and concurrent calls you need on day one and in three years. Ask the partner to price handsets, softphone seats and any module fees separately, and to state whether licensing changes at fixed user bands. Confirm how adding 50 users later is quoted.
Sites and WAN survivability
Each branch that needs local survival, such as a small survivable gateway or a second media path, adds hardware, a circuit review and extra testing. A single central server with no local fallback costs less to build but leaves branches dark when the WAN fails. Ask for a per-site bill of materials, the failover behavior tested for each site, and whether SIP trunks terminate centrally or locally, because that choice changes trunk and number costs.
911 and dispatchable location obligations
Direct 911 dialing, central notification and dispatchable location are design requirements, not add-ons. They add work in the dial plan, notification routing, location data maintenance for fixed and remote phones, and documented testing. Each of these recurs when staff move or new sites open. Ask the partner to quote the 911 design and test plan as a separate line, to name who maintains location records after go-live, and to state whether location updates for remote users are included or billed per change.
Contact center queues and recording
Queues, IVR, agent desktops, screen pops and call recording add build effort, storage and reporting work that a basic PBX does not carry. Recording retention drives storage cost for years, and sector rules may set the minimum. Commercial add-ons or open-source projects can fill gaps, each with its own license or support fee. Ask for queue strategy design, recording storage sizing with a retention period, reporting scope, and a list of every third-party component with its license and renewal cost.
High availability requirements
Redundant servers, database replication, shared storage and failover testing roughly double the infrastructure and the engineering hours compared with a single node. Availability targets are a business decision, so the cost should follow from a documented recovery objective rather than a default. Ask the partner to separate the one-time cost of building redundancy from the recurring cost of running and testing it, and to state how many failover tests are included in the first year.
Support model: in-house, partner or vendor
Who answers the phone at 2 a.m. determines a large share of recurring cost. An in-house team carries salaries, on-call rotation and training. A partner charges a retainer or per-incident rate, and a commercial vendor bundles support into a subscription. Compare the same scope across all three, including upgrades and security patches for Asterisk and FreePBX. Ask for the response windows in writing, the upgrade policy, who holds the vendor relationships, and what happens to support if the partner changes.
How self-hosted cost compares with per-user hosted phone plans
A per-user hosted phone plan bundles software, hosting, carrier connectivity and support into one recurring fee that rises with every seat you add. A self-hosted Asterisk or FreePBX build splits the same spend differently: infrastructure you run or rent, carrier services you buy per trunk and per number, and people (internal staff or a partner) who install, configure, secure and maintain the system. The useful comparison is not the monthly figure on a provider's pricing page against a server invoice. It is the total cost over the contract term, with each category tagged as one-time or recurring. Pull current price lists from each hosted provider directly, since per-user rates, bundles and minimums change, and do not use any figure from this page as a proxy.
Model the break-even over the term you expect to live with the system, typically the length of your carrier and hosting commitments. Start with seat growth: a per-user plan scales cost linearly with headcount, while a self-hosted server adds cost in steps as capacity, licenses for commercial modules and support tiers change. Then model add-ons, such as call recording, advanced reporting, contact center queues or additional softphone licenses, which hosted vendors often price separately. Next, count numbers and trunks. Carrier charges for DIDs, inbound minutes and emergency calling are usually similar under both models, so they should be compared line for line. Ask each hosted vendor which of these items are included, metered or extra.
Migration and exit are where the models diverge most. Ask hosted providers in writing how you export call detail records, recordings, voicemail, auto-attendant configurations and number port-out steps, and whether any of this carries a fee or a notice period. For the self-hosted build, the exit cost is the staff time to move dial plans and numbers, plus any commercial licenses that were tied to the platform. Put a clear exit plan into the contract scope with your implementation partner, and confirm with your carrier which porting timelines and charges apply at the end of the term.
How the cost mix shifts by deployment size
At a single site with a small user base, the cost mix is dominated by the one-time build and the recurring trunk and number charges. Hosting is usually a single virtual machine or a small on-premises server, so the infrastructure line is modest. Implementation effort is front-loaded into dial plan design, handset provisioning and a basic 911 configuration, and the bulk of recurring spend is usually the carrier relationship rather than the software itself.
- Trunks and numbers: Carrier charges for SIP trunking, direct inbound numbers and per-minute usage are often the largest recurring line. Ask the carrier to itemize them separately from any platform fees.
- Handsets and softphones: Desk phones are a one-time purchase per seat, while softphone licenses or client software may recur. Confirm which model your partner quotes.
- Hosting: A single small server or cloud instance with backups is typically a low recurring cost, but ask whether backup storage and monitoring are priced separately.
- Implementation and porting: Number porting, initial configuration and testing are one-time costs. Ask for porting to be quoted as a separate line with its own lead time.
- Support: Confirm whether the support retainer covers after-hours fixes, since a single site may still need them.
Before accepting a quote, confirm carrier, handset and hardware figures directly with each vendor, and ask the partner to show which costs recur each year.
A multi-site organization adds costs that scale with the number of locations rather than the number of users. Each site needs its own trunk path or survivable connection, its own dispatchable location for emergency calls, and often local handsets and paging. Central hosting becomes more valuable, but it also introduces a dependency on the wide area network, which can drive additional spend on redundant links or local survivability hardware.
- Survivability: Branch fallback, such as a local gateway or a secondary trunk, is a recurring hardware and licensing item. Ask how failover is priced and tested.
- Location services: Per-site emergency location configuration and its maintenance are added work. Ask the partner to price location updates for moves and new staff separately.
- WAN and connectivity: Dedicated circuits or SD-WAN links between sites may sit outside the telephony quote, so confirm who owns them.
- Porting across sites: Consolidating several legacy systems means more number porting events, each with its own sequencing and cost. Request a per-port or per-site breakdown.
- Dial plan and migration work: Mapping extensions and routes across sites is a one-time engineering effort that grows with the number of sites.
Ask the partner to quote each site as a separate line, so you can see which costs are central and which repeat per location.
Contact centers and regulated multi-site deployments carry the most cost lines beyond basic telephony. Call recording, storage retention, queue reporting, CRM integration and high availability hardware all add to the build, and each can recur. Regulated environments also add evidence and testing work, which is usually billed as professional services rather than included in platform costs.
- Recording storage: Storage volume and retention periods drive recurring cost. Ask how long recordings are kept, where they sit, and who pays for growth as call volume rises.
- High availability hardware: Redundant servers, shared storage or a second site add one-time and recurring costs. Confirm what is included in the quote and what is required for your uptime target.
- Location and emergency services: Dispatchable location and 911 testing across many endpoints are ongoing tasks. Ask for testing and documentation to be priced as a distinct deliverable.
- Commercial modules and reporting: Agent desktops, wallboards and supervisor tools may come from commercial add-ons or other projects. Ask for each module's license terms and support model.
- Compliance evidence: Retention settings, access logs and change records support audits. Ask whether the partner prepares this evidence and what it costs.
Confirm all licensing, storage and hardware figures with the vendors and carriers named in your quote, and ask which items are one-time and which recur.
How to build your own phone system cost estimate
This sequence turns a rough sense of telephony spend into a line-by-line estimate that separates one-time build work from recurring carrier, hosting and support costs, so you can compare it fairly with a per-user hosted phone quote for the same scope.
Inventory users, sites and devices
Start with a count of everyone who needs a phone number, grouped by site, role and device type: desk phones, softphones, mobile clients, analog lines for elevators or fax, and shared phones in lobbies or wards. Your IT team or telecom lead owns this list, and it is done when every extension has a site, a owner or function and a device type. Ask each SaaS vendor and implementation partner to price against this same list so user counts are not inflated in one quote and understated in another.
List trunks, concurrent calls and numbers
Measure the busiest concurrent call count per site from your current call detail records, not from headcount, and size SIP trunk channels from that peak plus growth you can document. Export the list of numbers you intend to keep, including direct inward dial ranges, toll-free numbers and fax lines, and mark which ones require a port. This step is done when you have a channel count, a number inventory and a porting list with the current carrier and account holder for each block. Request trunk pricing per channel, per number and per port from each carrier, with setup and porting fees shown separately.
Define 911 and location requirements
Document how emergency calls must route from every site and from remote or mobile users, including direct 911 dialing, internal notification, and how dispatchable location is captured and kept current. Confirm the requirements with your legal, facilities and emergency response owners and with the rules that apply to your sector. This step is complete when each location has a documented emergency design and a list of the services it needs. Ask every vendor to state in writing which 911 features are included, which are add-ons, and which depend on a third-party emergency service provider.
Set queue, IVR and recording requirements
Write down the call flows that must exist on day one: queues, auto-attendant menus, after-hours routing, voicemail, call recording and retention periods, and reporting. Record which of these need commercial modules or a separate contact center product, since those are often the largest variable in a PBX budget. The step is done when each flow has an owner, a retention period set by your records policy, and a yes or no for each feature. Ask vendors to itemize add-on modules, per-agent or per-seat fees, and storage costs for recordings.
Price hosting, carrier and hardware from quotes
Collect written quotes for the parts you will buy: compute or cloud hosting for the PBX and any session border controller, carrier minutes and per-channel charges, handsets, headsets and licenses for commercial add-ons. Mark each line as one-time or recurring and state the billing unit, such as per channel, per number or per device. This step is done when every infrastructure and carrier line is a quote, not an estimate, with the term length and any minimum commitment shown. Ask for the same unit definitions from each vendor so you can compare them directly.
Add implementation, porting and testing as a separate line
Keep implementation services apart from infrastructure so you can see the one-time cost clearly. Include dial plan design, number porting coordination, 911 testing, user migration, handset provisioning, documentation and staff training, and note who performs each task: your team, an implementation partner or the carrier. A fixed-scope written statement of work is the usual way to close this step, because it defines deliverables before work starts. Ask each partner for a fixed price tied to named deliverables, and ask what is excluded and how change requests are priced.
Model recurring support and upgrades over the term
Build a term schedule, usually the period you expect to keep the system before a major refresh, and add support contracts, software maintenance, upgrade work, monitoring, backups and carrier charges for each year. Note any version lifecycle events that will force upgrade work, and confirm them against the vendor's published lifecycle rather than assumptions. This step is done when you have a year-by-year total that separates fixed recurring costs from usage-based ones. Ask partners for their support hours, response commitments and upgrade policy in writing.
Compare the total with a per-user SaaS quote
Send the same user, site, trunk, 911, queue and recording inventory to at least one hosted phone provider and ask for a per-user price with every add-on, carrier charge, porting fee and 911 feature stated. Put both totals on the same term and currency, and list what each option leaves for you to operate. The sequence is complete when you have one comparison table covering one-time and recurring costs for the self-hosted and SaaS options. Confirm with the SaaS provider where call data is stored and which controls you can audit.
Questions buyers ask before they hire help on phone system cost
How much effort does an in-house Asterisk or FreePBX build take?
The effort depends on the number of users, sites, trunks and features, and on how much of the work your team has done before. An in-house build usually covers server design, SIP trunk setup, dial plans, handset provisioning, call routing, voicemail, backup, monitoring and emergency calling rules, and each of these needs testing before cutover. Ask your team to list every component on paper and estimate hours for each, then compare that list with the scope in a partner's written quote. Gaps in the list are where projects overrun.
What skills does an open-source phone system build require?
A build needs people who understand Linux server administration, SIP signaling, NAT and firewall traversal, codecs, and dial plan logic. Someone must also own telephony-specific compliance work, such as direct 911 dialing and dispatchable location, along with call recording, number porting and carrier troubleshooting. Most teams find the hardest part is not the first install but the ongoing operation: patching, lifecycle upgrades, and diagnosing one-way audio or registration failures under real call volume. Check which of these skills you already have in-house and which you would hire or contract for.
Can our team deploy the phone system without outside help?
Many teams can, if they have people with the skills above and enough time to test thoroughly before go-live. The question is less about capability and more about risk: who is accountable if a carrier change or a 911 routing test fails at 2 a.m. Consider a hybrid model in which your staff owns operations while an implementation partner handles design, testing and documentation for compliance evidence. DeployOpen plans, implements, integrates, hardens and documents self-hosted platforms inside your own infrastructure, typically under a fixed scope agreed in writing before work starts.
How long does a phone system implementation take, and what drives it?
Length depends on the number of sites, the number of users and devices, the number of trunks and numbers to port, whether queues or IVR are included, and how many integrations are required. Compliance work such as 911 location mapping and testing adds time, as does any change to an existing carrier contract. Ask any partner to show the phases, the dependencies between them, and the decision points that could move the schedule. A timeline that does not name these drivers is not yet a plan.
What do we need to provide before an implementation starts?
Prepare a users list with extensions and roles, a site list with addresses and floor or room details for emergency location, and the current trunk and number inventory. You will also need carrier account access or a letter of authorization, agreed change windows for cutover, and named owners on your side for telecom, networking, security and business approvals. Missing owners and late carrier access are among the most common causes of delay. Confirm these responsibilities in the written scope so that neither side assumes the other is handling them.
What recurring costs follow go-live on an open-source PBX?
After go-live, recurring costs usually include hosting or cloud infrastructure, SIP trunk and number charges from your carrier, handset replacement and licensing for any commercial modules you choose, and support or retainer fees if you buy ongoing help. Operational work also recurs: security patching, upgrades that follow the Asterisk lifecycle, backup testing, dial plan changes, and periodic 911 testing. Ask any quote to separate one-time costs from monthly or annual items, and to state what is included in ongoing support and what triggers extra charges.
How does number porting affect the schedule and cost of a phone system project?
Number porting moves your phone numbers from your current carrier to the new trunk provider, and carriers process it on their own timelines. The porting request can be rejected if account details, service addresses or authorization letters do not match exactly, which pushes cutover back. Plan porting early, confirm each number's status and service address, and decide which numbers can move in phases. Ask the carrier and your partner to confirm the porting lead time in writing, since it is usually the longest step outside your control.
What should a written phone system quote include?
A useful quote lists the scope by site and user group, the deliverables such as design documents, test records and runbooks, and the fixed scope or assumptions behind the price. It should separate one-time implementation work from recurring hosting, carrier, licensing and support items, and name who pays for each. Ask how 911 testing and documentation are handled, what happens if carrier porting slips, and how changes to scope are priced. Compare the quote against your requirements checklist rather than against the lowest total, because missing items usually reappear later as change requests.
How DeployOpen scopes and prices a phone system implementation
DeployOpen plans, implements, integrates, hardens, documents and supports self-hosted open-source telephony inside your own cloud accounts, data centers or air-gapped networks. Cost questions are settled in a written scope before any build work starts, so each cost component is visible and traceable to a deliverable.
How we scope
- Engagements are fixed-scope, with deliverables and timelines agreed in writing before work starts
- Scope lists each cost owner: hosting, SIP trunks and numbers, handsets, commercial modules, implementation and porting
- Written scope separates one-time build work from recurring support, upgrades and licensing decisions
How we build
- Sizing covers users, sites, concurrent calls and trunk capacity so server and hosting costs match real load
- Porting, dial plan migration and 911 configuration are scoped as separate line items with their own test steps
- Commercial modules and support contracts are evaluated and costed only where your requirements call for them
How we hand over
- Handover includes configuration documentation, runbooks and a written cost model for recurring items
- Test records for call flows, 911 routing and failover are delivered as evidence for your own assessors
- Your team receives the ongoing cost picture, including which items recur and what drives them up
How we support
- Ongoing support, upgrades and monitoring are available as retainers, priced separately from the build
- Retainer scope should name who handles trunk changes, version upgrades and after-hours incidents
- Quotes should state what the retainer excludes, such as carrier charges and handset replacement
