Measurement & Verification (M&V)

The cheapest and cleanest unit of energy is the one you never use. But proving you didn't use it is harder than it sounds, because you're trying to measure something that, by definition, never happened.

This is where Measurement & Verification (M&V) comes in. M&V is the process used to plan, quantify and report the energy, cost and carbon savings attributable to an energy efficiency or decarbonisation project.

The best practice standard for M&V, and the basis for this guide, is the International Performance Measurement & Verification Protocol (IPMVP).

This guide explains what M&V is, why it matters and how IPMVP works in practice, alongside real-world use cases and practical applications. Whether you're commissioning M&V or reviewing someone else's numbers, you'll know what ‘good’ M&V looks like.

Your project is complete. The invoices have been paid, the equipment is operational and the business case says you should be saving a healthy amount each year. Then your Finance Director asks: how much are we actually saving?

It sounds like a straightforward question. In practice, it isn't.

M&V exists to answer that question in a structured, standardised way. Rather than simply comparing energy consumption before and after a project, it uses measured energy data alongside the factors that influence consumption (weather, occupancy, operating hours, production volumes) to build a robust counterfactual baseline: what energy use would have looked like under the same conditions if the project hadn't happened. Actual post-project consumption is then compared against that baseline, and the difference is the saving attributable to the project.

This approach matters because a simple before-and-after comparison of meter data can be misleading. Energy consumption changes for plenty of reasons that have nothing to do with an efficiency project: weather, occupancy, operating hours, production levels, how a building is used. A building might use more energy after an efficiency project than before, but that doesn't mean the project failed. It may simply mean consumption would have been even higher without it.

That's the core purpose of M&V: to separate the impact of a specific project from everything else that influences energy consumption, and provide credible evidence of the savings actually achieved.

Below is a step-by-step illustration of the core M&V process: metering a full cycle (often 12 months for larger schemes) of baseline data, building a model from it, installing the Energy Efficiency Measure (EEM), then projecting that same model forward as the counterfactual against what was actually metered afterwards.

The International Performance Measurement and Verification Protocol (IPMVP) is the long-standing global best practice framework for measuring and verifying energy savings, developed and maintained by the Efficiency Valuation Organization (EVO).

IPMVP is not a detailed ‘how to’ guide, but sets out the standardised good practice principles, processes and procedures that should be followed so that savings calculations are transparent, comparable and trusted.

Six key principles underpin an IPMVP-quality M&V approach

Accuracy

Use an appropriate level of measurement and analysis for the value and complexity of the project.

Completeness

Account for all material factors affecting energy performance, both within and outside the measurement boundary.

Conservatism

Where uncertainty exists, avoid overstating savings.

Consistency

Use a methodology that allows performance to be compared fairly over time and between projects.

Relevance

Focus measurement and analysis on the factors that actually influence the project's performance.

Transparency

Document the data, assumptions, calculations and judgements so another party can understand and reproduce the result.

M&V versus monitoring

M&V is not the same as monitoring, though the two are frequently conflated. Energy monitoring tells you what energy consumption is doing. M&V goes further: it uses measured data and an agreed methodology to determine how much of the change in monitored energy use can reasonably be attributed to a particular project. Monitoring is therefore an important input to M&V, but it isn't M&V itself.

IPMVP provides four recognised approaches for determining a project's savings. The appropriate approach depends on what you are trying to measure, where the measurement boundary is drawn, the data available and the level of confidence required, particularly where there are commercial outcomes riding on the result: for example, projects with performance guarantees or where a supplier retains ongoing maintenance responsibilities.

The underlying principle is the same for all four: establish what energy use would have been without the project, then compare it with what actually happened. The difference between the Options is in what you measure and where you draw the measurement boundary.

Which Option should you use?

As a basic rule of thumb:

• AOption A is typically used where the parameter(s) driving the saving can be measured reliably on their own, but measuring everything needed for full before-and-after consumption isn't practical or proportionate (e.g. a lighting retrofit, where wattage is measured but operating hours are estimated).
• BOption B is typically used where the equipment or system can be isolated and metered directly, provided there's time for a long enough period of metering to capture a baseline and the cost of the additional sub-metering is proportionate.
• COption C can be used where several measures are implemented together and isolating an individual measure isn't practical or required. It often benefits from the reliability of fiscal energy data.
• DOption D can be used where there's no pre-existing consumption data to build a baseline from, such as a new building.

These are only rules of thumb. There is no single ‘best’ M&V Option. The approach should be chosen to suit the project and provide a reliable, practical and cost-effective way of determining the savings.

What this means for you: your M&V provider should be able to explain why the chosen Option is appropriate for your project. If they can't, ask them to set out the approach, the data required and how it will demonstrate the savings.

In accordance with IPMVP, every credible M&V exercise should follow the same broad sequence, whether it is a single lighting upgrade or a multi-site Energy Performance Contract (EPC).

1. 01

   Develop an M&V Plan

   Sets out how the savings will be calculated and reported, before the project is implemented.

   A crucial reference document setting out the agreed ‘rules of the game’: the scope of the project, the IPMVP Option to be used, the baseline, the metering and data that will be used, how changes will be treated, and how savings will be quantified, verified and reported. Because savings are often calculated using a mathematical model, rather than being measured directly, this agreement helps build certainty around the modelling process and stops the parties reaching different conclusions from the same data later on.

   For anything linked to contractual payments or funding decisions, ensure the M&V Plan is independently verified (to IPMVP standards) and signed off by all parties before it is written into the contract.

2. 02

   Collect and validate data

   Assemble the evidence needed for robust analysis, as specified in the M&V Plan.

   Good M&V depends on more than meter readings. You may also need weather data, occupancy and operating hours data, Building Management System (BMS) data, and a record of anything unusual that happened on site: power cuts, generator tests or one-off events. Before analysis starts, check the data is complete, uses the right meters, and reflects normal operation. Poor-quality data creates baseline errors that are hard to fix later.

   Modern metering and analytics tools can flag that consumption has changed far faster than a monthly bill ever could, but they cannot tell you why. That still takes someone who knows what happened on site.

3. 03

   Develop the baseline model

   Predict expected energy use as if the project hadn't happened.

   The baseline model predicts what the building would have consumed without the project. Since savings cannot be measured directly, they are calculated as the gap between this prediction and what was actually metered. For simple projects this may just be a pre-installation measurement; for whole-building projects (Option C) it is usually built with regression analysis, modelling daily, weekly or monthly energy consumption against variables like temperature (via degree days), occupancy or production. A well-built baseline model is representative, accounts for the key variables, is transparent enough to reproduce, and is documented in the M&V Plan.

   A baseline model should not just be built; it should be tested. Good practice checks it two ways: does it make engineering sense (heating use, for example, should clearly track outside temperature), and does it perform well against statistical checks such as how much of past energy use it explains, how accurately it predicts, and whether it is biased toward over- or under-predicting. A model that passes the statistical tests but does not reflect how the building actually operates should still be treated with caution.

4. 04

   Implement the project

   And verify it was correctly installed and commissioned.

   Installing new equipment does not automatically deliver savings. An operational verification step means confirming the installation matches the specification, checking control strategies and schedules, and verifying meters and sensors are working correctly, so the project can be confirmed as capable of achieving its anticipated savings before monitoring begins.

5. 05

   Monitor performance

   Collect energy and operational data throughout the reporting period.

   Throughout the agreed reporting period (as defined in the M&V Plan), energy and operational data is collected to compare against the baseline and, just as importantly, anything that changes on site is recorded. M&V is an ongoing process, not a single calculation at the end. Regular monitoring catches problems early and builds the evidence base for the final numbers.

6. 06

   Calculate savings

   Apply the agreed M&V methodology to determine the savings.

   The methodology set out in the M&V Plan is applied to the reporting-period data, with routine adjustments (for predictable factors like weather) and non-routine adjustments (for one-off changes, like extended opening hours or power cuts) applied so the result reflects only the project's impact. Where payments or guarantees are at stake, independent verification can be used to check that the methodology was correctly applied and the savings accurately reported.

7. 07

   Report & verify savings

   Communicate results and use the findings to optimise future performance.

   The final step is to report the savings and, where required, have them independently verified. A good M&V report does not just state a savings figure; it provides an audit trail setting out how that figure was derived: the methodology and IPMVP Option used, the baseline and any adjustments applied, measured consumption and the resulting verified savings, alongside key assumptions and any uncertainty.

   Independent verification can be a condition of funding, a requirement under energy performance contracts, or simply good practice when results will be reported to a board or the public. It means someone with no stake in the outcome externally audits that the report follows the M&V Plan, that there are no errors or misstatements, and that the savings can be reproduced from the data.

   A figure that cannot be explained should not be treated as verified. Beyond proving the project worked, comparing actual against expected performance over time also flags opportunities to optimise further, which is why M&V is as useful for improving a project as it is for judging it.

Measurement & Verification is intended to provide an objective assessment of the savings delivered by an energy or decarbonisation project. Where the results determine supplier payments, performance guarantees, funding releases, investment decisions or other significant commercial outcomes, having an independent party involved can provide an important additional layer of confidence.

There are two ways an independent M&V provider can add value:

In both cases, independence helps reduce the potential for commercial interests to influence the outcome.

M&V involves professional judgement. Establishing the approach requires decisions about the appropriate method and measurement boundary, baseline period, which variables influence energy consumption, how changes in operating conditions should be accounted for and how unusual events should be treated. Different reasonable assumptions can sometimes produce materially different estimates of savings.

Where the party calculating the savings also has a financial interest in the result, there is an inherent potential for conflict of interest. Independent M&V provides greater separation between the project outcome and the organisation responsible for determining or reporting the savings.

For customers and funders, this can provide:

• Greater confidence that reported savings are credible and independently assessed
• Reduced risk when payments or investment decisions depend on project performance
• Greater transparency around assumptions, calculations and evidence
• A defensible evidence base for boards, auditors, funders and other stakeholders
• Consistency in how savings are calculated and reported

For suppliers and project developers, independent M&V can also strengthen the credibility of their performance claims. A saving verified by an independent specialist is more readily trusted than a saving that has simply been self-reported.

“

Just as financial auditors protect the integrity of a set of accounts, independent M&V protects the integrity of a reported energy saving, creating trust precisely where the customer's and the supplier's interests diverge. In practice that means acting as referee, fact-checker, and often the glue that holds a performance relationship together once real money is riding on the number.”

Ian Jeffries, Managing Director, EEVS

Measurement & Verification is a specialist discipline, and the quality of the people carrying it out can have a significant impact on the reliability of the results. EVO oversees two professional M&V qualifications, providing a recognised framework for developing M&V knowledge and expertise:

What qualification should you look for?

A qualification is useful evidence of M&V knowledge and competence, but it is not a guarantee of the quality of an individual assignment. When appointing an M&V professional, you should also consider their practical experience, understanding of your project, approach to data and analysis, and ability to explain and defend their methodology.

For more complex projects, it is particularly important that the person responsible for the M&V has the appropriate level of experience to develop and justify the methodology, rather than simply holding a qualification.

Buildings are dynamic, and energy use is influenced by many factors beyond the measures themselves. Good M&V recognises this, accounts for them transparently, and makes sure reported savings fairly represent the project's impact. For example:

M&V can be applied to almost any energy efficiency or decarbonisation project where you need to understand what savings have actually been achieved. The level of M&V should be proportionate to the size, complexity and commercial importance of the project. The following are some of the most common applications:

A handful of habits separate M&V that holds up under scrutiny from M&V that does not.

1. 01Agree the M&V Plan and baseline models before work starts, and (where possible) write them into the contract, not just the tender documents.
2. 02Match the rigour to the value at stake. A £15k lighting upgrade does not need the scrutiny of a multi-million-pound energy performance contract.
3. 03Insist on independent verification wherever savings determine a payment or a claim your board will rely on.
4. 04Keep a record of anything that changes during the reporting period: occupancy, opening hours, refurbishments. Failure to do so is a major source of M&V disputes.
5. 05Build M&V into the tender or spec from the outset, not as an afterthought once a supplier is chosen.
6. 06Ensure suppliers confirm their approach: ask what IPMVP Option is being proposed and why, and who is qualified (PMVA, PMVE or CMVP) to review it.

Going back to the question this guide opened with: your Finance Director asking how much a project actually saved. There is no shortcut to that answer. Savings can't be read off a meter; they have to be calculated. But with the right M&V approach in place from the start, it is always an answerable question. In summary:

• Savings can't be measured directly.

  They only exist by comparison: actual consumption against a modelled counterfactual of what would have happened without the project. That's the problem M&V exists to solve.

• IPMVP makes that comparison credible.

  Six principles (accurate, complete, conservative, consistent, relevant, transparent) and four measurement Options (A–D) give everyone (customer, supplier, funder) a shared, standardised way to calculate and check a savings figure.

• The process is the same shape whatever the scale.

  Plan, collect data, build the baseline, implement, monitor, calculate, report. Get the M&V Plan agreed before the project starts, put good governance in place to follow it, and allow issues to be resolved as they arise rather than letting them harden into disputes.

• Independence builds trust precisely where commercial interests diverge.

  Wherever a saving determines a payment, a guarantee, or a number your board will rely on, independent M&V (or independent verification of a supplier's own numbers) is what turns a claimed saving into a defensible one.

• There's no single ‘right’ approach.

  Only the approach that's proportionate to what's at stake, and robust enough to survive being challenged.

Quick definitions for the terms used throughout this guide.

AMR

Automatic Meter Reading: meters that transmit consumption data remotely at frequent intervals, rather than being read manually.

CMVP

Certified Measurement & Verification Professional. The M&V certification awarded by the Association of Energy Engineers (AEE).

Counterfactual baseline

The energy consumption a building or system would have had without the project: the reference point savings are measured against.

Degree days

A measure of how much colder or warmer a period was than a building's base temperature, the outdoor temperature above which no further heating (or below which no further cooling) is needed. Building-specific, though 15.5°C is a common default for heating in offices. Heating (HDD) and cooling (CDD) degree days are used to normalise consumption for weather in baseline models.

EEM

Energy Efficiency Measure: a project or intervention intended to reduce energy consumption, such as a boiler upgrade or lighting retrofit. Also known as an Energy Conservation Measure (ECM); IPMVP moved from ECM to EEM in its latest edition.

Fiscal meter

The meter used for billing purposes, often the main utility meter used as the data source for whole-building (Option C) M&V.

Gain-share

A commercial arrangement where savings, and sometimes the cost of achieving them, are shared between customer and supplier.

IPMVP Option

One of four standard IPMVP approaches (A to D) to calculating savings, chosen to match the project type and required accuracy.

Measurement boundary

The boundary drawn around what is actually being measured: narrower for single-measure projects (Options A/B), wider for whole-building approaches (Option C).

Non-routine adjustment

An adjustment for one-off or unplanned changes, such as extended opening hours or a temporary closure.

Operational verification

Confirming an installed measure is commissioned correctly and operating as intended, before savings are assessed.

Regression analysis

A statistical technique used to model the relationship between energy use and variables like temperature or occupancy, commonly used to build Option C baseline models and calculate routine adjustments.

Routine adjustment

An adjustment for predictable, expected-to-vary factors, most commonly external temperature via degree days.

EEVS is the UK's largest independent team of Measurement & Verification (M&V) specialists.

1. Efficiency Valuation Organization (EVO), International Performance Measurement and Verification Protocol: Core Concepts 2022 (EVO 10000-1:2022), March 2022.
2. EVO, IPMVP Core Concepts 2022 (EVO 10000-1:2022), Section 5.1, p.20.
3. Greater London Authority, GLA 82615 RE:FIT 5 – National Carbon and Energy Performance Contracting Framework, Find a Tender notice 010988-2025; Zero Carbon Accelerator, “RE:FIT 5: The Mayor of London's new energy performance contracting framework”, 18 November 2025.
4. Scottish Government, Non-Domestic Energy Efficiency Framework (over £1m projects) 2020–2024: buyer's guide.
5. Real Decreto 36/2023, de 24 de enero, por el que se establece un sistema de Certificados de Ahorro Energético (BOE-A-2023-2027), Articles 2(k) and 12.4.
6. EVO, IPMVP Core Concepts 2022 (EVO 10000-1:2022), Section 13.1.3, p.78.