Electrical Estimate Revision Control: How to Compare Revisions Without Repricing the Entire Project
Every tender moves after you start pricing. Drawings are reissued, a supplier updates a quote, or the builder adds a floor. The question is whether you reprice the whole job each time or only what changed. Electrical estimate revision control is what makes the second option safe.
This guide covers how to set up estimate version control, how to compare Revision A and Revision B, how to apply delta pricing, and how to decide what to reprice and what to carry over. It focuses on managing your own estimate versions, not on finding changes in the tender documents.
Why Full Repricing Wastes Time and Adds Risk
Repricing everything on every change has three costs:
- Time. You re-measure and re-price areas that have not changed, while the tender deadline does not move.
- New errors. Each full pass is a chance to change an unchanged item by accident, such as a different cable rate or a missed line, and nobody notices.
- No explanation. If the total moves and you cannot say which lines caused it, you cannot defend the number to the builder or your own director.
Partial repricing is only safe if you know exactly what changed and can prove everything else did not. That is what revision control provides.
Setting Up Electrical Estimate Revision Control
Lock your baseline. When you finish a review or issue a price, save that version as read-only. Never overwrite it. Every later comparison depends on Revision A staying exactly as it was. A clean baseline is easier to build if the original follows a consistent process, as set out in the step-by-step process of preparing an electrical estimate.
Use a naming convention. Include the project code, document type, revision and date, for example PRJ2291_Estimate_RevB_2026-10-06. Use letters for estimate revisions and keep them separate from drawing revision numbers. Record which drawing and specification revisions each estimate revision is based on.
Know your triggers. A revised electrical estimate is usually prompted by changed documents, a client scope change, a new or expired supplier quote, or a correction to your own work. Log the trigger every time.
Keep a revision register. One table for the whole job:
Rev | Date | Based on | Trigger | Total (ex-GST) | Change | Prepared / checked |
A | 22 Sep | Drawings Rev 2, spec Rev 1 | Initial tender | $412,500 | n/a | JS / PM |
B | 02 Oct | Drawings Rev 3, MSB re-quote | Revised documents, new quote | $429,918 | +$17,418 | JS / PM |
Maintain an estimate change log. For every changed line, record the item reference, description, reason, quantity before and after, rate, cost change and source document. The register shows the headline. The change log shows the detail.
How to Compare Estimate Revisions Step by Step
To compare estimate revisions reliably, work in this order:
- Confirm both versions are locked and note which document sets each one is based on.
- Start from the list of document changes you have already identified. The comparison here is between your two estimates.
- Map each change to estimate lines and cost codes. One drawing change can touch several packages.
- Classify each change: added, deleted, quantity changed, specification changed, or price changed.
- Price only the delta, using the same rates, overhead and margin as Revision A unless you have a reason to change them, and say so if you do.
- Reconcile. Revision A plus the net delta must equal Revision B. Then run a line-by-line comparison of the unchanged items. Every one should show zero variance. Any difference is an unintended change.
Step 6 is the one that is skipped most often, and it is the one that catches mistakes.
Delta Pricing Worked Example
Delta pricing means pricing the difference between revisions rather than the whole job. The figures below are illustrative only, not market rates.
Revision A is $412,500 ex-GST. Revision B changes the lighting layout, adds containment, removes some power outlets and upsizes the main switchboard.
Change | Type | Basis | Direct cost change |
LED panels added | Added | 36 at $118 | +$4,248 |
LED panels removed | Deleted | 12 at $118 | -$1,416 |
Cable tray added | Added | 120 m at $48/m | +$5,760 |
General power outlets removed | Deleted | 18 at $103 | -$1,854 |
Main switchboard upsized | Price changed | New quote $38,600 vs $31,200 | +$7,400 |
Net direct change | +$14,138 |
Apply the same combined overhead and margin used in Revision A (23.2% in this example): $14,138 × 1.232 = $17,418.
Revision B = $412,500 + $17,418 = $429,918, a change of about 4.2%.
You now have a total, a reason for every dollar of movement, and an unchanged baseline to point back to.
What to Reprice and What to Carry Over
Reprice | Carry over |
Items with changed quantity, specification or location | Items with the same drawing reference and scope |
Items with a new, updated or expired supplier quote | Items with a valid, unchanged quote |
Items whose installation conditions changed (height, access, staging) | Labour assumptions that the change does not affect |
Flow-on items affected by a change | Rates, overhead and margin that remain appropriate |
Allowances that are now defined | Allowances that are still undefined |
Check for ripple effects. A larger switchboard can change cable sizes, upstream protection, containment and the space it needs. Ask what else the changed item touches before you carry anything over.
Know when to stop patching. If a change affects whole systems or a large part of the scope, a full reprice may be safer. There is no fixed rule, but many estimators set an internal threshold and record the decision in the change log.
If you need a fast, controlled revision turnaround and your team is already stretched, our electrical estimating services can maintain the revision register and price the deltas for you.
Tools: Spreadsheet or Takeoff Software
Spreadsheets. Save each revision as its own locked workbook. Add a comparison sheet that matches lines by item reference (using lookup formulas) and shows quantity, rate and cost variance side by side, with conditional formatting to highlight any non-zero difference. It is simple and flexible, but it relies on disciplined item references.
Takeoff software. Many platforms support drawing version comparison and quantity change reports, and they keep takeoff history attached to each revision. Check what your own software supports before relying on it. For a broader view, see digital takeoff vs manual estimating and the benefits of electrical estimating software for contractors.
Either way, the tool only helps if every line has a stable reference that survives from one revision to the next.
Reporting Changes to the Client
Builders do not want a new price with no explanation. Send a one-page revision summary:
- Revision, date and documents it is based on
- Previous total, new total and net change
- Changes grouped by package, with short descriptions
- Any change to assumptions or qualifications
- Items that need a decision from the client
A short example:
Revision B summary. Net change +$17,418 (ex-GST) on Revision A. Increases relate to additional lighting, cable tray and an upsized main switchboard. Reductions relate to removed power outlets. Pricing assumptions are unchanged.
This applies before the award. Once a contract is in place, changes move into the variation process, covered in electrical variation estimating.
Keep an Audit Trail
Keep every revision, the change log, the source documents and the supplier quotes with their validity dates. Record who prepared and who checked each version. If a price is questioned, you lose a tender and want to know why, or the job is handed to the delivery team, you can show exactly how the number was built and when it changed.
Common Mistakes
Overwriting the previous version. You lose the baseline and cannot prove what changed.
Not recording the basis. A revision without its document revisions listed cannot be checked later.
Skipping the reconciliation. If Revision A plus the delta does not equal Revision B, something has moved that you did not intend.
Ignoring flow-on costs. Pricing the visible change and missing what it triggers is the most common way to underprice a revision.
Using stale rates or quotes. Carrying over an expired quote because the item “did not change” quietly adds risk.
Frequently Asked Questions
What is electrical estimate revision control?
It is the process of naming, locking, logging and comparing each version of an estimate so you can show exactly what changed between versions and why the price moved.
What is delta pricing?
Delta pricing means pricing only the difference between two revisions, using the same rates and markups as the earlier version, then adding the net change to the previous total.
When should I reprice the whole project instead?
When the change affects entire systems, touches a large share of the scope, or you cannot confidently identify what has changed. Record the decision and the reason in your change log.
How do I compare two estimate revisions in Excel?
Keep each revision as a locked workbook with stable item references. Build a comparison sheet that matches lines by reference and shows quantity, rate and cost variance, and highlights non-zero differences on lines that should be unchanged.
Final Takeaway
Good electrical estimate revision control lets you reprice only what changed, explain every dollar of movement and keep a record you can defend. Lock the baseline, log every change, price the delta and reconcile the totals.
Want a hand managing revisions on your next tender? Contact our estimating team to discuss your project.
