Interval data vs monthly bills: what each one is good for

The same building can produce nearly identical monthly bills two years running and hide a completely different story underneath. A monthly bill tells you what you paid. Interval data tells you when the load happened, how sharp the peaks were, and whether something is running that should not be. Both are useful. The mistake is treating one as a substitute for the other.

What each data set actually is

Monthly billing data is roughly 12 readings a year per meter, plus demand and cost line items. Interval data is a reading taken every 15 minutes or every hour. The gap in resolution is enormous: a monthly bill provides 12 data points a year while a smart meter produces more than 35,000, specifically 96 reads a day and 35,040 a year at 15-minute granularity. That is why meter-level data now exists at scale, with US utilities reporting about 119 million advanced metering installations, near 72% of all electric meters.

Granularity and what it supports

Why interval data changes M&V and fault detection

For measurement and verification, resolution drives precision. High-frequency meter data is typically at 15-minute or hourly intervals, with hourly models reaching useful accuracy that monthly billing data cannot match, and IPMVP-grade savings verification depends on that granularity. Interval data also enables fault detection: a chiller that never fully cycles off overnight shows up as a raised baseload long before it shows up on a bill. Research now pairs the IPMVP framework with automated anomaly detection precisely because interval data makes deviations visible.

The cost of granularity: storage and volume

Interval data is your largest dataset by a wide margin. A utility running 10,000 15-minute meters generates roughly 35 million interval readings a month, which is why interval data belongs in time-series-oriented storage rather than the one-row-per-month tables that billing systems were built around. If you plan to keep years of history for trend analysis and M&V baselines, size for that from the start.

When you need which

• Reach for monthly bills when the job is settlement, budgeting, accruals, cost allocation, or a quick portfolio cost view.
• Reach for interval data when the job is demand charge diagnosis, peak reduction, fault detection, savings verification, or matching load to a tariff's time-of-use windows.
• Use both for anything that has to be defensible: interval explains the behavior, and the bill confirms what it cost.

You still need both

Monthly bills remain the source of truth for what you owe, complete with the delivery charges, riders, and taxes that interval data never carries. Interval data explains the shape behind those charges but does not settle them. Reading load profiles well, separating baseload from peak, is its own skill worth building, and whichever stream you ingest, the formats vary enough that standardizing them is half the work. Keep the two aligned to the same meters and periods and you get the full picture: interval explains, bills settle.