Repair or Replace? A Lifecycle-Cost Worksheet for Building Equipment

Compare repair and replacement over the same period, for the same required service, using dated evidence for every important cost. A repair invoice and a replacement quote are only the starting amounts. Energy, maintenance, later repairs, interruptions and remaining value can change the result.

This guide provides a practical worksheet for owners and facilities managers comparing one building asset. It explains a method, not a recommendation for a particular purchase. First establish which options can meet the building’s actual operating requirements; a lower modeled cost does not establish technical suitability.

Define the service before comparing prices

Write a short decision statement: identify the asset, the service it must provide, the problem being addressed and the date by which a decision is needed. For example: “Compare a documented repair with a complete replacement proposal for the same occupied-space heating requirement over five years.” Define the hours, capacity and operating conditions that matter to that project.

Ask each provider to identify what its proposal includes and excludes. Your worksheet needs a complete repair scope and a complete replacement scope, not a component price on one side and a finished project on the other. Include access work, controls, commissioning, disposal and other enabling work where they actually apply. Record unresolved items separately instead of silently treating them as free.

A condition assessment supplies the technical basis for the repair option. Record the diagnosed issue, the proposed corrective work and what remains uncertain afterward. Do not turn the age of an asset into a prediction of its exact failure date, or a warranty term into a promised service life.

Use a common comparison period

NIST Handbook 135, August 2025, explains lifecycle-cost analysis for federal facilities and identifies the need for a common study period when comparing mutually exclusive alternatives. Its underlying approach can also inform private-sector analysis; its federal requirements are not automatically a private owner’s rules.

For your worksheet, write the start date, comparison end date and the reason for that horizon. A planned building sale, lease end or major renovation may be relevant. A short holding period and a long operating horizon answer different questions. Apply the chosen dates consistently to both options.

If a repaired asset is not expected to provide service throughout that period, show the later replacement and its timing. “Repair now” may really mean “repair now, replace in year three.” Identify that sequence explicitly. Conversely, do not erase the remaining service value of a new asset simply because the worksheet stops before its expected life ends.

Build an evidence ledger

Use the following fields for each option. Keep a source filename, date and responsible person alongside each entry so someone else can reconstruct the comparison.

Unknown is a useful entry. Assign an owner and a next step to it. A blank cell can otherwise be mistaken for zero. Preserve the original quotes and service history even after entering their values; a spreadsheet total cannot explain an excluded labor charge or a changed operating assumption.

For priced maintenance scopes, use the maintenance contract bid comparison guide to reconcile included tasks and exclusions. That article compares service offers; this worksheet compares the future costs of the asset alternatives.

Put cash flows on a dated timeline

Create one row for each cost event, with its amount and timing. Separate immediate project costs from recurring expenses and later capital work. Identify any credit or residual value with an explicit sign convention: in a total-cost calculation it reduces cost.

Exclude money already spent that the present decision cannot change. NIST calls these sunk costs. A past repair may supply evidence about condition or recurring problems, but adding the old invoice to only one future option would answer a different question.

Keep dollars and discount assumptions consistent. Constant-dollar estimates use a real discount rate; estimates including general inflation use a nominal rate. NIST distinguishes these approaches. This guide does not supply a required rate for your business or a current federal rate. Have the person accountable for the analysis specify the basis and document it.

For a simple year-end cash-flow convention, the present value of a cost in year t is its future amount divided by (1 + r) raised to t, where r is the annual discount rate in decimal form. A year-zero expense is not discounted. State your timing convention; deposits, delayed installation and monthly charges may require a more detailed model.

A fictional five-year calculation

The numbers below are invented solely to demonstrate the worksheet. They are not equipment prices, failure forecasts, savings claims or a recommended discount rate. Assume both alternatives meet the required service for five years, immediate work occurs at year zero, annual costs occur at each year end, and all figures are constant dollars. Use an illustrative 3 percent real discount rate and no real escalation.

The five annual discount factors sum to approximately 4.579707. Repair therefore totals $3,000 + $2,500 × 4.579707 + $2,000 ÷ 1.03³. Replacement totals $11,000 + $1,000 × 4.579707 − $2,000 ÷ 1.03⁵. Calculations use unrounded factors; displayed amounts are rounded to cents.

Under those assumptions, replacement has approximately $2,425.06 lower modeled cost. This result belongs to that invented scenario. It does not establish that an actual asset should be replaced, or that the assumed five-year service and residual value are achievable.

The immediate cash requirement is still $11,000 for replacement versus $3,000 for repair. Keep that funding question visible alongside the present-value comparison. A discounted total is not an invoice, a financing offer or the amount of cash required this month.

Test the assumptions that could reverse the result

Change an uncertain input and recalculate before presenting a preferred scenario. Start with assumptions whose evidence is weakest or whose amounts are large enough to affect the decision. Keep a record of the original value, changed value and resulting difference.

For example, change only the fictional repair scenario’s annual cost from $2,500 to $1,500. Its total becomes approximately $11,699.84, which is $2,154.65 below the unchanged replacement scenario. The apparent preference reverses. That is a reason to improve the operating-cost evidence, not a prediction that either number is correct.

NIST’s uncertainty chapter describes sensitivity analysis and explains that it does not establish the probability of an outcome. For this private-owner worksheet, test supported ranges for repair timing, operating expense and residual value. Keep correlated assumptions coherent: do not describe a collection of unrelated best-case figures as an expected outcome.

If the result depends on an unsupported future resale value or a guessed service life, show that dependency prominently. Label a scenario “unresolved pending evidence” when that better describes it than “lowest lifecycle cost.”

Keep interruptions, warranties and constraints explicit

Write an interruption scenario in ordinary language before assigning dollars: what stops, for how long, and what additional expense follows? Separate a planned installation shutdown from an unplanned failure scenario. Do not count the same consequence twice through both a lost-revenue estimate and another overlapping loss category.

When a consequence cannot be valued credibly, describe it separately. A decision memo can say that a particular service interruption is unacceptable without pretending that a precise probability or dollar loss was measured. Likewise, financing, insurance, tax treatment, incentives and eligibility can require a separate project-specific analysis. Do not enter an assumed rebate as a guaranteed reduction.

For warranty claims, list the applicable document, covered parts or services, exclusions, time limits and who confirmed applicability. A warranty does not automatically pay for every repair expense. If coverage is uncertain, retain the gross cost and show the proposed adjustment as an unresolved scenario.

Turn the worksheet into a reviewable decision

Keep a concise decision memo with the calculation. State the options considered, common service requirement and dates; identify the lowest modeled cost under each scenario; and list constraints, uncertainties and who must resolve them. Attach the source ledger and the dated cash-flow rows.

The DOE Building Life Cycle Cost Programs page points to NIST’s BLCC tools and related resources. The 2025 BLCC User Guide publication record identifies Technical Note 2346. This article did not run BLCC or validate a project in that application.

For an actual federal project, confirm the applicable current methodology, annual factors and agency requirements. Handbook 135’s 2025 edition notes that its examples retain older data; copying an example rate is not verification of current inputs. For a private project, document the owner’s chosen assumptions rather than presenting federal defaults as universal.

Frequently asked questions

Is there a universal repair-cost percentage that means replace?

This worksheet does not establish one. Compare the documented alternatives over a common period and identify the assumptions, service requirements and constraints that drive the result.

Should I include what I already spent repairing the equipment?

Exclude past costs that the present decision cannot change from the future-cost comparison. Keep the service history as evidence of condition and recurring issues.

Does the lowest lifecycle cost mean the smallest upfront payment?

No. Present-value cost combines costs over time. Show the immediate cash requirement and funding constraints separately.

Does the fictional 3 percent rate apply to my project?

No. It is an arithmetic example. Document the appropriate rate and inflation basis for the actual analysis; federal projects must follow their applicable current requirements.

Sources and scope

Sources checked October 27, 2026: NIST HB135e2025, August 2025, particularly study periods, discounting, cost estimation and uncertainty; DOE BLCC program resources; and NIST TN2346 publication record, August 19, 2025. Handbook sections were read through retrieved primary-source text; some direct automated NIST downloads returned HTTP403. The fictional arithmetic was independently recalculated. No actual bids, customer asset, financial advice, technical suitability assessment, hands-on testing or outside professional review is represented.

AI tools assisted with drafting. ClearTrade Report Editorial Team checked the cited sources and edited this guide. No hands-on inspection or testing was performed.