Interval Data & AMI Meters: Using Your Data to Negotiate Better Rates

What an AMI meter records

Advanced metering infrastructure, the industry term for a smart meter, records consumption in fixed intervals and reports it back to the utility, instead of accumulating a single monthly total for a meter reader. As of 2022, U.S. utilities had about 119 million AMI installations, about 72 percent of all electric meters, and about 88 percent of those were residential [eia-ami-faq], so commercial coverage varies more than the headline number suggests. Larger commercial accounts have often had interval meters for demand billing since long before AMI, because a demand charge cannot be computed without one.

The interval is typically 15 minutes, though some utilities bill on 30-minute demand; ComEd's delivery classes, for instance, are defined on 30-minute demand [comed-rate-rds]. Either way, a year of data is a long list of timestamps and kWh values: 35,040 rows for 15-minute data, 17,520 for 30-minute. Divide each interval's kWh by the interval length in hours and you have average kW for that window, which is the number the utility uses to set your billed demand. The demand charges page explains that mechanic.

Getting the data: Green Button

Green Button is the common format utilities use to hand customers their own usage data. It came out of a 2012 White House call for utilities to give customers secure access to their data, and it is built on the Energy Services Provider Interface standard, an XML format that can carry data at 15-minute, hourly, daily, or monthly intervals [doe-green-button]. DOE lists more than 50 utilities and suppliers committed to the standard, covering more than 60 million homes and businesses, including PG&E, Southern California Edison, National Grid, and American Electric Power [doe-green-button].

There are two flavors.

Download My Data. You log in to the utility portal and download a file. The Green Button Alliance describes it as a consistent XML format, in contrast to the varied CSV exports utilities used to offer [gba-download-my-data]. It is a one-time snapshot; you download again when you want newer data.

Connect My Data. You authorize a third party, and the utility sends the data to them directly over an automated connection. The Green Button Alliance describes the customer defining how long the authorization lasts and being able to revoke it at any time, with utilities able to deliver intervals from one minute to monthly depending on the meter [gba-connect-my-data]. The standard is NAESB REQ.21 and it separates personally identifiable information into a stream distinct from the usage data itself [gba-connect-my-data]. This is the flavor a broker or energy management platform wants, because it keeps flowing.

If your utility does not offer Green Button, most still provide interval data on request, sometimes as a CSV from the business account team. Ask for "interval usage data, 15-minute, kWh, for the last 12 months, for account number X."

Reading your load shape

Once you have the file, three views tell you almost everything.

The daily profile. Average each interval across all days in a month and plot 96 points. A grow's profile is a plateau with sharp edges: a step up when flower lights come on, a smaller step when veg lights come on, a step down at lights-off, with HVAC riding on top. If the edges of every room line up, you will see one tall step. If rooms are staggered, you will see stairs. The tall step is what sets your demand charge.

The peak interval. Sort the whole year by kW and look at the top ten intervals. What day, what time, what was running. The peak is often not lights-on. It can be a maintenance day when every room was tested at once, a heat wave when HVAC stacked on lighting, or a drying room's dehumidifiers all cycling together.

Load factor. The EIA defines load factor as the ratio of average load to peak load over a specified interval [eia-glossary-l]. Compute it for the month: monthly kWh divided by (peak kW × hours in the month). A facility that used 200,000 kWh in a 720-hour month with a 500 kW peak has a load factor of 200,000 ÷ (500 × 720) = 0.56, or 56 percent. A grow with staggered rooms and steady HVAC can run 60 to 75 percent. An office runs 30 to 40. A facility that peaks once and idles runs lower still.

Every number in this example is an input we chose. The point is the formula, which you can run on your own data in a spreadsheet in five minutes. See peak demand vs. peak usage for why the ratio matters more than either number alone.

How suppliers price load factor

In a competitive state, a supplier quoting you a fixed price per kWh is building it from components: energy, priced hour by hour off the wholesale forward curve; capacity, allocated by your share of the regional peak; transmission and ancillary charges; losses; risk premium; and margin. Interval data changes several of those.

• Energy. A load that is flat around the clock buys a lot of cheap overnight energy. A load concentrated in the afternoon buys expensive on-peak energy. Your interval data tells the supplier which you are, and the price follows. Two facilities with identical monthly kWh can get different fixed prices for this reason alone.
• Capacity. In PJM, NYISO, and ISO-NE, your capacity cost depends on what you drew during a handful of system peak hours. A supplier with your intervals can estimate your peak-hour draw precisely; without them, it assumes a class-average profile, which for a 24-hour grow is usually worse than the truth. That is why cultivators often see better pricing once real data is on the table.
• Risk premium. Suppliers charge for uncertainty. A year of intervals removes most of it. A new facility with three months of data and a build-out coming gets a fatter premium because the supplier is guessing at the shape.
• Volume tolerance. Fixed contracts have bandwidth clauses that let the supplier re-price if you use much more or less than expected. Interval data lets you negotiate a wider band from a documented baseline instead of the supplier's guess. The contract structures page covers how bandwidth and swing work in fixed, index, and block-and-index products.

The upshot is that a high-load-factor facility, which describes most indoor grows, is a customer suppliers want. If you have never sent interval data with a request for pricing, you have probably been quoted as if you were a class-average commercial building, and you are leaving money on the table. This is one of the main reasons a broker who shops multiple suppliers can find a better price than a direct quote; see energy broker vs direct supplier.

What to send a broker or supplier

A complete package looks like this:

1. Twelve months of interval data per meter, 15- or 30-minute, in Green Button XML or CSV, or a Connect My Data authorization so it can be pulled directly.
2. Twelve months of bills for the same meters, so the interval data can be reconciled to billed kWh and demand. The bill walk-through shows the lines that matter.
3. The utility account and meter numbers, the rate class shown on the bill, and the service voltage.
4. The current supply contract, if any: supplier, price, term, end date, and the notice and termination provisions.
5. What is changing. Rooms coming online, a lighting retrofit planned, a photoperiod change, a new chiller. Suppliers will price a known change; they charge extra for a surprise.
6. What you want. Budget certainty, lowest expected cost, renewable content, or a particular term length. Different products fit different goals, and the supplier contract comparison worksheet lays them side by side.

Most of that comes from the utility portal in an afternoon. If pulling it feels like a project, that is usually the sign the facility has never had a real procurement done.

Privacy: who can see your intervals

Interval data reveals when you run lights, how many rooms you have, and roughly when you harvest. It is worth being deliberate about who gets it.

The rule at most utilities is that customer-specific usage data is released only with the customer's authorization. California wrote this down formally: the CPUC's Decision 11-07-056 adopted rules to protect the privacy and security of electricity usage data for PG&E, SCE, and SDG&E customers, built on the Fair Information Practice Principles, and it applies to third parties that receive data with customer consent [cpuc-d-11-07-056]. Other states have their own versions, and the Green Button Connect standard was designed with revocable, time-limited customer authorization as its core [gba-connect-my-data].

Practical steps:

• Sign a letter of authorization or a Connect My Data consent that names the recipient and the purpose. Do not hand over portal credentials.
• Set an end date on the authorization, and revoke it when the engagement ends.
• Ask a broker who receives your data how it is stored and whether it is shared with suppliers in identified or anonymized form. Suppliers need the shape; they do not need your name on it until you are ready to contract.
• Treat interval data like a financial statement. It is one.