Low voltage estimating is the work of turning a drawing set and a spec book into a priced, scoped proposal for cabling, security, audio-visual, and the other systems that run below line voltage. Done well, it comes down to four habits: read the specs before you count anything, write down what you include and exclude, take off by system, and price labor from your own history. This guide walks through that method the way a low-voltage sub's estimator would use it on a real bid.
TL;DR
- Define scope first. Specs and drawings together decide what is yours, what belongs to the electrical sub, and what the owner supplies.
- Take off by system, floor, and phase, and mark finished areas so you can see what you skipped.
- Price labor from your own crews' productivity, then apply overhead, profit, and contingency one way only so nothing is counted twice.
- Most losses come from scope gaps: pathway, firestopping, programming, testing, and commissioning that nobody priced.
- Track every invitation and due date in one place. A great estimate is worth nothing if it misses bid day.
Table of Contents
- What low voltage estimating covers
- Read the documents before you count anything
- Run the takeoff by system
- Price labor from your own numbers
- Materials, vendor quotes, overhead, and contingency
- Scope gaps that cost low-voltage subs money
- Tracking invitations and due dates
- Perspective: why we think estimating should live next to the job
- Where Subascent fits
- FAQ
- Sources
What low voltage estimating covers
"Low voltage" is a loose label. In commercial work it usually points at Division 27 (communications) and parts of Division 28 (electronic safety and security). One firm might do all of it. Most low-voltage subs pick a lane.
Typical systems an estimator prices:
- Structured cabling: Cat 6 or 6A copper, fiber backbone, patch panels, racks, and telecom rooms.
- Security: access control, video surveillance, intercom, and intrusion detection.
- Audio-visual: displays, conferencing, paging, and sound systems.
- Specialty communications: distributed antenna systems, nurse call, and wireless access point cabling.
- Fire alarm, where local rules and the spec place it with the low-voltage sub rather than the electrical or fire protection sub.
The estimate has to cover more than devices and cable. It includes pathway where you own it, terminations, labeling, testing and certification, as-built documents, programming, training, and warranty. The hardware is often the easy part to count. The labor around it is where bids drift.
Read the documents before you count anything
Start with the specifications, not the plans. Read Division 27 and 28 in full, then the sections that touch them: Division 26 for raceway and power, Division 07 for firestopping, and Division 01 for submittals, closeout, and schedule demands.
Then work through this list:
- Log every addendum and bulletin. A single revised sheet can move a rack room or add 40 cameras.
- Flag conflicts between drawings and specs. Write them up as RFIs before bid day, not after you win.
- Read the General Conditions. They set financial terms like retainage, sales tax exemptions, bond requirements, and temporary power responsibilities, and each one changes your number.
- Write the scope boundary. Who supplies conduit and back boxes? Who pulls the cable in conduit? Who provides the network switches and the cloud licensing? Who does the final connections to door hardware?
Put your inclusions and exclusions on paper while you read, not at the end. If you want a pattern for it, our guide on bid proposal exclusions shows how to word them so a GC can't read them two ways. For the bigger picture of what belongs in any trade scope, see what a trade bid scope includes.
Run the takeoff by system
A low voltage takeoff has three kinds of quantities: counts (devices, outlets, cameras, readers), linear measurements (cable runs, conduit, J-hook paths), and allowances (programming hours, commissioning days).
Organize the work so you can audit it:
- Split quantities by system, building, floor, phase, area, or alternate. A single bucket called "cabling" hides mistakes.
- Record assumptions as you go: ceiling height, assumed pathway, cable slack, who owns the core drilling.
- Mark each area as complete on the plans. Omissions are much easier to spot on a sheet with half the floor unmarked.
For cable lengths, don't just measure the straight line from device to rack. Follow the real path along the corridor, add vertical drops, add service loops at both ends, and add waste. Many estimators build a standard allowance per drop from past jobs, then adjust for long runs.
Working from PDFs saves time on counts and lengths. We cover the mechanics in electrical takeoff from PDF, and the same layer-by-system approach applies to low-voltage drawings.
A quick worked example
Say a two-story medical office has 96 data drops, 12 cameras, 8 card readers, and two telecom rooms. Your takeoff sheet might show:
| System | Count | Notes |
|---|---|---|
| Data drops (Cat 6A) | 96 | Average run from your routed path, plus slack |
| Cameras | 12 | Includes mounts and PoE connections |
| Card readers | 8 | Door hardware and power supplies by others |
| Racks and patch panels | 2 rooms | Grounding and labeling included |
| Testing and as-builts | 1 lot | Certification report per drop |
The numbers are illustrative, not a benchmark. The point is the structure: every line has a count, a unit, and a note saying what is and is not included.
Price labor from your own numbers
Published labor units are a starting point. Your crews, your typical ceiling types, and your pathway conditions decide what the work really costs. The best estimators track hours per drop, per camera, and per reader on finished jobs, then feed those actuals back into the next bid.
For a method to build and check units, our electrical labor units worked examples show how to turn a published unit into a number that fits your own shop. The masonry article on how labor units work explains the same logic in another trade.
Adjust base units for conditions:
- Ceiling height and access: lifts or scaffolds slow every drop.
- Occupied space versus new construction.
- Pathway: open ceilings, hard lids, and conduit all change pull time.
- Remote or phased work that adds mobilization.
- Testing and labeling requirements stricter than your normal practice.
Don't forget equipment. Lifts, trailers, and specialty testers cost money whether you rent or own them. Our equipment costing guide shows how to put those costs in the bid.
Materials, vendor quotes, overhead, and contingency
Get distributor quotes on the big-ticket items: cameras, access control panels, switches, racks, and fiber. Note the quote date and its validity period. Material prices on electronics move, and a quote that expires before award is a risk you are carrying.
When a vendor quote or allowance is in your number, say so in the proposal. Aligning the proposal with the final estimate and stating allowances and vendor quotes accurately cuts down on bid-day scope drift.
Then add the markup layers in a fixed order:
- Direct labor, with burden.
- Materials, with tax where it applies.
- Equipment and subcontracted work, such as core drilling or firestopping.
- Overhead, which recovers office and home-office costs.
- Contingency, which covers project-specific risk.
- Profit.
Apply each one once. If your unit rates already carry overhead, don't add overhead again on the proposal total. Mixing methods is how a bid ends up several percent higher than you meant, or lower because you thought something was already in.
How much markup is right? There's no single answer. According to AWCI, successful bidding involves judgment about overhead, profit margins, customer relations, and how badly you want the job. Set your overhead from your real annual costs, then let risk, competition, and backlog move profit and contingency job by job. Our post on electrical job costing mistakes shows what happens when overhead is guessed rather than measured.
Scope gaps that cost low-voltage subs money
Most low-voltage losses aren't math errors. They're things nobody priced. Check each of these before you submit:
| Gap | What to check |
|---|---|
| Pathway | Who supplies conduit, sleeves, J-hooks, cable tray, and back boxes? |
| Firestopping | Is penetration sealing yours, the electrical sub's, or a separate trade's? |
| Power | Who provides outlets and circuits for racks, cameras, and readers? |
| Programming and commissioning | Are hours for head-end setup, camera views, and credentials in the number? |
| Licensing and cloud fees | Are software licenses included, and for how many years? |
| Testing and documentation | Does the spec require certification reports, as-builts, and O&M manuals? |
| Network equipment | Who owns switches, UPS units, and the IT handoff? |
| Phasing and schedule | Is there night work, multiple mobilizations, or an owner move-in date? |
| Warranty | How long, and does it include labor and callbacks? |
Write each answer as an inclusion, an exclusion, or a qualification in the proposal. If a GC asks you to level your number against another low-voltage bid, the clearer your proposal reads, the less you have to defend. See bid leveling for trade subs for how the other side compares numbers.
Tracking invitations and due dates
A low-voltage sub often bids to a dozen or more GCs at once. Invitations arrive by email, through GC portals, and by phone. Due dates are often different from the date for questions, and addenda can shift both.
Keep one list with these fields for each bid:
- GC and contact
- Project name and location
- Bid due date and time, including time zone
- RFI deadline
- Addenda received
- Scope assigned: which systems you are pricing
- Status: reviewing, pricing, submitted, won, lost
If you are new to a market, a plain approach still works: call local GCs, ask to be added to their bid lists, and ask for their estimator. Then keep that list current, because every missed due date is a lost chance to price a job.
Perspective: why we think estimating should live next to the job
We built Subascent for specialty trade subs because the estimate, the bid list, and the job all feed each other. The takeoff counts become the budget. The budget becomes the line you compare against actual hours. That comparison is what makes your next low voltage estimate better.
Most software made for general contractors starts from a different place. It tracks owners, schedules across trades, and draws. A low-voltage sub's problems are narrower and sharper: a bid list that's too long, a takeoff that eats evenings, a scope with five systems and four different bosses, and a field crew whose hours never get back to the office.
Our advice: whatever tool you use, make sure your actual hours per drop, per camera, and per reader come back from the field and land next to the estimate. Without that, you're guessing at labor on every bid.
— Dave
Where Subascent fits
Subascent is job and bid management software for specialty trade subs, including low-voltage and electrical contractors. It brings bid tracking, estimating, PDF takeoff (a paid add-on), submittals and RFIs, change orders, daily reports, and QuickBooks sync into one place. Foremen get the free CrewTrack mobile app with the subscription, so field hours can feed your next estimate. You can see how it works at Subascent.
FAQ
What is a low voltage contractor?
A low voltage contractor installs systems that run on low-power circuits: data cabling, security, access control, audio-visual, and similar communications systems. On commercial projects they usually work as a specialty subcontractor to a GC or the electrical sub. The exact systems vary by firm and by what the spec assigns.
How do I price a low voltage job if I have no labor history?
Start with published labor units and distributor pricing, then add conditions such as ceiling height and access. Track real hours on your first jobs by system and unit. After a few projects, replace the published numbers with your own.
Do I need estimating software for low voltage work?
A spreadsheet works for a handful of small bids. Software starts to pay off when you are bidding many jobs, measuring from PDFs, reusing assemblies, and comparing estimates to actual hours. The deciding factor is whether the tool connects the bid to the job after you win.
What should a low voltage proposal state?
It should list inclusions, exclusions, and qualifications. Stating them explicitly clarifies bid scope and responsibilities. Cover pathway, power, firestopping, programming, testing, licenses, and warranty.
Sources
- Estimating Techniques, Electrical Resources (PDF)
- Electrical Scope of Work Estimating Guide
- Estimating: Aiming for Accuracy, AWCI