MEP engineers design and document the mechanical, electrical, and plumbing systems in buildings. Solo consultants and small firms bill architects, developers, general contractors, and building owners for design phases, site surveys, load calculations, permit drawings, and construction-phase support. Invoices usually tie to project phases, hourly time, or a percentage of work completed.
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MEP work is priced three main ways. Hourly time-and-materials is common for small tenant improvements, field surveys, code reviews, and open-ended coordination, with different rates for principal, project engineer, and CAD/BIM technician. Lump-sum fees by phase (schematic design, design development, construction documents, bidding, construction administration) are typical for new construction and larger renovations, and are billed as a percentage of each phase complete. Some firms quote a percentage of construction cost, often in the range of 8 to 15 percent of the MEP construction cost on commercial work, but small projects are more often fixed per drawing set or per square foot. Reimbursable expenses such as plan printing, permit filing fees, travel, and sub-consultants (for example a fire protection or commissioning specialist) are usually billed at cost plus a 10 to 15 percent markup, as stated in your agreement. Additional services such as revisions after design approval, owner-driven scope changes, and extra site visits are billed separately from the base fee.
| Service | Priced | Typical range |
|---|---|---|
| Principal / PE engineer time | per hour | $150-250 |
| Project engineer or designer time | per hour | $95-160 |
| CAD / Revit drafting technician | per hour | $65-110 |
| Existing conditions site survey and report | flat fee | $800-3,500 |
| Tenant improvement MEP design (small office or retail) | per sq ft | $1.50-4.50 |
| Heating and cooling load calculations (Manual J/N style or ASHRAE) | flat fee | $500-2,500 |
| Permit-ready construction drawing set (small commercial) | flat fee | $4,000-18,000 |
| Construction administration (RFIs, submittal review, site visits) | per hour | $130-220 |
Typical US ranges. Rates vary by region, experience, and job size.
| Description | Qty | Rate | Amount |
|---|---|---|---|
| Tenant improvement MEP design, 4,200 sq ft office - Construction Documents phase (60% of $9,450 phase fee) | 1 flat fee | $5,670.00 | $5,670.00 |
| Existing conditions site survey and mechanical equipment report | 1 flat fee | $1,400.00 | $1,400.00 |
| Principal engineer time - coordination with architect and utility provider | 4.5 hours | $185.00 | $832.50 |
| CAD technician time - revisions per architect's revised floor plan (Additional Service) | 6 hours | $85.00 | $510.00 |
| Plan set printing and permit submittal fee advance (reimbursable, at cost + 10%) | 1 lot | $264.00 | $264.00 |
| Total | $8,676.50 | ||
Notes: Project: Suite 300 TI, 1200 Commerce St. Contract dated March 3. Invoice 2 of 4 for design fees. Payment due within 30 days of invoice date. A 1.5% monthly late fee applies to balances past due. Additional services are billed at contract hourly rates. Please reference project number on payment.
Clients and accounts payable departments handle many projects at once. A consistent project number gets your invoice coded and paid faster.
Tying each line to the signed agreement makes it clear what is base scope and what is billed under the contract's hourly or additional services terms.
For lump-sum work, owners and lenders expect to see the phase, total phase fee, percent billed to date, and the amount billed this period.
Revisions caused by architect changes, owner changes, or new code comments should be itemized and dated so they are not mistaken for base scope errors.
Clients may audit hourly billing. Showing role, hours, and rate supports the charge without needing a follow-up.
Printing, permit fees, courier, mileage, and sub-consultant costs need to match what your agreement allows. Separate lines avoid disputes over markup.
Many firms include license information on proposals and invoices, and some clients or public agencies require it. Check your state board rules for what applies to you.
Corporate and institutional clients often reject invoices without a PO number, and lender-funded projects may require a matching draw reference.
Most MEP consultants require a retainer or initial payment of 10 to 25 percent of the fee, or a flat amount for small jobs, before starting work. Progress invoices are then sent monthly or at phase completion, with net 30 the most common term, though some general contractors and developers push for net 45 or 60. Late fees of 1 to 1.5 percent per month are common if stated in the contract, and check your state's rules on allowable interest. Some firms stop issuing stamped drawings until overdue balances are cleared, but that should be stated in the agreement. Payment is usually by ACH, check, or wire for large invoices, with credit cards used mostly for small residential or one-off work.
A construction documents phase can last two or three months. Invoice the percent complete each month so you are not carrying the work until the end of the phase.
Track revisions, owner-requested changes, and extra site visits with dates and a short note on who requested them. Send a written change notice before doing the work when the cost is significant.
Releasing stamped permit sets before payment removes your leverage. Put a clause in your agreement that sealed documents are released on payment, and apply it consistently.
If you bring in a fire protection, controls, or commissioning sub-consultant, show their invoice amount and your markup as a separate line. Pay terms from the client may be slower than what you owe the sub, so check the agreement for pay-when-paid language.
Construction-phase work is unpredictable. Hourly billing with a not-to-exceed budget keeps you covered when RFIs and submittals run beyond what you expected.
Flat fees by phase work well when the scope is clear, such as a defined tenant improvement or new building with fixed drawings. Hourly is safer for surveys, code studies, existing building work with unknowns, and construction administration. Many firms use both on one project.
Yes, if your agreement defines the approved design as the baseline and lists revisions as additional services. Document the change request, the date, and the hours, and bill at your contract hourly rates.
Requirements vary by state and client. It is common to include it on proposals and drawings, and some public or institutional clients ask for it on invoices. Check with your state engineering board and your client's contract.
Send a reminder at the due date, then a written notice referencing the late fee and any clause on withholding sealed documents. For unpaid design work, many states allow lien rights for design professionals on certain projects, but the rules and deadlines vary, so check with a local attorney.
Professional engineering services are not taxed in many states, but some states tax certain services or tangible items such as printed plan sets. Check with your state department of revenue or a tax professional.
Send a MEP Engineer estimate for approval, then turn it into an invoice when the work is done.
MEP Engineer estimate template