Energy audit vs ongoing energy monitoring: which one moves the numbers

Owners searching for an energy audit in Ontario usually want one of two things: a list of measures with paybacks, or evidence for a board or a lender that the building is being looked after. An audit delivers both. What it does not deliver is the next eighteen months, during which schedules drift, a boiler is left in hand, a tenant changes, and the savings quietly disappear.

This article compares the audit with ongoing monitoring and targeting, and argues that for most portfolios the question is not either or; it is which one you are missing.

What an energy audit is

ASHRAE Standard 211 defines the procedures for energy audit Levels 1, 2 and 3 and sets minimum reporting requirements. In broad terms a Level 1 audit is a walk-through with a utility bill review, a Level 2 adds a detailed survey and analysis with costed measures, and a Level 3 is an investment-grade analysis of capital projects. All three are point-in-time studies delivered as a report.

The value of an audit is discovery. A good auditor finds the oversized pump, the simultaneous heating and cooling, the domestic hot water recirculation running at the wrong temperature. The audit report becomes the priorities section of the action plan.

What ongoing monitoring is

Monitoring and targeting (M&T) is the management discipline of treating energy as a controllable resource: measure it continuously, model what it should be given weather and occupancy, compare actual against expected, and act on the difference. The Bureau of Energy Efficiency's M&T chapter describes the key tool, CUSUM, as the running difference between baseline (expected) consumption and actual consumption; the line oscillates around zero until something changes the pattern, for better or worse.

For building portfolios, monitoring runs at the utility meter. Each month the bills and Green Button data are captured, validated and put on one calendar, intensities are recomputed, and the results are compared with last year and with the baseline. In VE-MAP that produces a monthly review report with priorities and a calendar, so the findings land with the people who can act.

Side by side

• Timing. Audit: once, or every few years. Monitoring: every month.
• Question answered. Audit: what could we save? Monitoring: what are we saving, and where did it stop?
• Data. Audit: a site visit plus one to three years of bills. Monitoring: every bill and interval feed, continuously, with validation.
• Output. Audit: a report with measures and paybacks. Monitoring: a trend, a variance, a short list of actions, and a verified savings figure.
• Weather. Audit: normalized once at the time of study. Monitoring: normalized every period using heating and cooling degree days, which Environment and Climate Change Canada defines against an 18 degree Celsius base.
• Cost structure. Audit: a project fee per building. Monitoring: a subscription per meter or site.

Why audit savings erode

Audit recommendations assume the building is operated as described in the report. Operations change. Setpoints are overridden after a complaint and never reset. A replacement contractor programs a schedule differently. A new tenant runs a data closet. Each of these is small and invisible on a total bill, and each is obvious on a CUSUM chart, where the slope turns up within a month or two of the change.

Monitoring also catches the class of problem an audit cannot: billing errors. A bill that does not match the meter, a duplicate invoice, an estimated read that was never trued up. The validation article covers what to check.

What each one costs, and what each one returns

An audit is a project fee per building, scaled by size and by level. Its return is the list of measures, and the return is only realized if the measures are implemented and stay implemented. Monitoring is a subscription per meter or per site. Its return is twofold: the savings it protects (drift caught in month two instead of month fourteen) and the savings it finds on its own (billing errors, schedule creep, base load growth, leaks visible in water intensity). For a portfolio where audits have already been done, the second category is often the larger one in the first year, simply because nobody has been looking.

The two also differ in who does the work afterward. An audit report is handed to the owner, who must find the time and the people to act on it. A monitoring service comes with a reviewer whose job is to read the numbers each month and bring the property team a short list. That difference, not the analytics, is why monitoring programs keep producing savings after the audit binder has gone on the shelf.

When you need the audit first

If a building has never been assessed, or a major capital decision is pending (boiler plant, chiller, envelope), get the audit. Monitoring will tell you a building is 30 percent above its peers; it will not tell you which piece of equipment to replace. Ontario buildings that already report under EWRB have a head start, because the benchmark position tells you which buildings deserve a Level 2 audit first.

When you need monitoring first

If audits have already been done and the measures implemented, monitoring is the missing piece. It is also the right first step when the portfolio is large and the budget for audits is limited: rank the buildings by intensity and variance, then audit the worst. The use cases page shows how multi-site and public sector portfolios sequence this.

How the two connect in VE-MAP

1. Audit measures are entered as priorities with owners and dates.
2. The baseline period is set before implementation, from validated bill and meter data.
3. Each month, actual consumption is compared with the weather-adjusted baseline; CUSUM and M&V tables show cumulative savings, following the whole-facility approach the IPMVP describes as Option C.
4. Drift shows up as a slope change; the review report names it and assigns a follow-up.
5. At year end, the annual benchmark report records where the building landed relative to its peers.

FAQ

Can monitoring replace an audit for EWRB or municipal reporting?

Reporting programs require consumption data, not an audit. Monitoring produces the data; an audit is separate. Toronto's by-law additionally requires buildings of 100,000 square feet and larger to have a certified professional verify their data once every five years.

How much data do you need before monitoring is meaningful?

Twelve months of validated bills gives a baseline that covers a heating and a cooling season. Interval data adds the daily and hourly shape; see interval data heat maps.

Do you perform audits?

VE-MAP is the monitoring and management service. We work alongside the auditor your organization chooses, and the audit findings become priorities in the plan.