Topic hub
Earned value management and cost contingency
EVM the way the contract actually requires it. CPI failure modes, cost vs schedule contingency, EVM under NEC4, and the maturity model that distinguishes a working controls function from one going through the motions.
About this topic
Earned value management (EVM) is the controls technique that integrates scope, schedule and cost into a single set of performance metrics. The mechanics are simple — Budgeted Cost of Work Scheduled (BCWS or PV), Budgeted Cost of Work Performed (BCWP or EV), Actual Cost of Work Performed (ACWP or AC), and the derived performance indices CPI (= EV/AC) and SPI (= EV/PV) — but the discipline behind them is not. Done properly, EVM gives a project sponsor the earliest credible signal that a programme is over-running on cost or schedule, typically three to six months before the same signal would be visible from cost or schedule reporting alone.
On UK public-sector and defence programmes, EVM is increasingly contractually mandated. The ANSI/EIA-748 standard sets out the 32 guidelines an Earned Value Management System (EVMS) must satisfy to be considered compliant. NEC4 expects an Accepted Programme that supports earned value reporting; UK defence programmes operating under DEF STAN frameworks specify ANSI/EIA-748 compliance and reference AACE 11R-88 for implementation. AACE International’s Earned Value Professional (EVP) credential and the broader Total Cost Management framework set out the practitioner standards. Forecasts — Estimate at Completion (EAC) and Estimate to Complete (ETC) — are derived from the performance indices but should always be cross-checked against a bottom-up forecast from the delivery team.
A working Performance Measurement Baseline (PMB) is the foundation. It is the time-phased, resource-loaded budget against which performance is measured, formally baselined and put under change control. Without a credible PMB, every EVM number downstream is suspect — CPI and SPI become artefacts of the baseline rather than indicators of delivery. On MoD contracts the PMB is typically reviewed at an Integrated Baseline Review (IBR) within ninety days of contract award; on commercial NEC4 work the Accepted Programme plays the equivalent role.
The two common failure modes are not technical. The first is CPI and SPI being read as health metrics when they are in fact lag indicators that can be flattered by data-collection practices that do not reflect what is actually happening on site. The second is the conflation of cost contingency and schedule contingency — they answer different questions, sit in different parts of the model, and are owned by different people. The guides below cover both, plus the maturity ladder that distinguishes an EVM function generating actionable signals from one that is producing reports nobody acts on.
Guides on this topic
7 guides in this cluster
Guide
When CPI Is Lying — The Hidden Failure Modes of Earned Value
Why your CPI and SPI can look healthy on a project that is quietly falling apart, what to look at instead, and when to abandon earned value altogether.
10 min read
Guide
Cost vs Schedule Contingency — and Why Teams Confuse Them
The structural difference between cost and schedule contingency, how three-point estimates feed both, the EMV vs QRA distinction, and how to defend the contingency number in a board paper.
10 min read
Guide
Budget at Completion (BAC): Formula, Worked Example, and Where Projects Get It Wrong
A practitioner's walkthrough of how BAC is set, how it relates to EAC, VAC and EVM, and the housekeeping mistakes that quietly invalidate the metric on real programmes.
7 min read
Guide
Earned Value Management Under NEC4 — What the Contract Actually Requires
How EVM and NEC4 interact, what the contract demands, and how to build a system that satisfies both the commercial team and the programme director.
9 min read
Guide
Project Controls Day Rates UK 2026 — Benchmarks by Role and Sector
Realistic day rate benchmarks for planners, cost engineers, risk managers and PMO leads across UK infrastructure — inside and outside IR35.
7 min read
Guide
Project Controls Maturity — What "Good" Actually Looks Like
A practical view of what a well-run controls function looks like on a real programme — single source of truth, monthly cadence, honest reporting — without the five-level pyramid.
10 min read
Guide
Reporting That Actually Gets Read at Steering Group
Why most controls reports are ignored, what an effective monthly pack looks like, and how to calibrate to the audience without diluting the message.
10 min read
Frequently asked
Earned value (EVM) and cost contingency — questions we get asked
- When is EVM contractually required on a UK programme?
- NEC4 expects an Accepted Programme that supports earned value reporting; UK defence programmes operating under DEF STAN often specify ANSI/EIA-748 compliance. Public-sector capital programmes funded under HM Treasury Green Book typically expect an EVM-grade reporting structure on schemes above a defined threshold. Outside those frames, EVM is good practice rather than mandated.
- Why is CPI sometimes a misleading indicator?
- CPI is a lag indicator that depends on disciplined progress measurement. Where progress is recorded by activity manager judgement rather than by deliverable-based earning rules, CPI can flatter genuinely under-performing programmes — especially in the months before a major hand-back or invoice cycle. The fix is not to abandon CPI but to back it up with deliverable-based earning rules and an independent estimate-to-complete check.
- What’s the difference between cost and schedule contingency?
- Cost contingency is the budget held against quantitative cost risk — the QCRA P50/P80 outcome, less the deterministic estimate. Schedule contingency is float — calendar time held against quantitative schedule risk. They answer different questions, are owned by different people, and trading one for the other (“we’ll buy time with money”) requires explicit modelling, not assumption.
- What is ANSI/EIA-748 and does it apply to UK contracts?
- ANSI/EIA-748 is the US-origin standard that sets out the 32 management-system guidelines an EVMS must satisfy to be considered compliant. It is referenced contractually on UK MoD programmes operating under DEF STAN frameworks and on some non-defence GMPP programmes. Compliance is normally demonstrated through an EVMS description document and validated at an Integrated Baseline Review within ninety days of contract award.
- How is EAC calculated and which formula is most defensible?
- Estimate at Completion can be calculated several ways. The performance-index formula EAC = AC + (BAC − EV) / CPI assumes future work performs at the historical cost-efficiency rate. A composite EAC using both CPI and SPI assumes both indices persist. The most defensible position at gateway review is to publish the index-based EAC alongside a bottom-up forecast from the delivery team and reconcile the gap — a divergence of more than 5–10% is a signal worth investigating, not a reason to pick a number.
- What does the AACE EVP credential cover?
- The Earned Value Professional (EVP) credential is AACE International’s certification for practitioners running EVM at programme level. It tests the candidate against ANSI/EIA-748 guideline knowledge, PMB development, performance analysis, forecasting, and change-control discipline. UK defence and infrastructure clients increasingly expect EVP or equivalent on EVMS-mandated contracts; it is the most widely recognised practitioner standard in this space.
Got a programme where this matters?
Most engagements start with a short call. We work out whether we’re the right fit, then come back with a short scoping note — scope, duration, team, indicative cost.