Before interpreting a utility portal or home monitor, identify what each field measures and the period it covers. A utility import total, a household-consumption estimate and a plug-level reading can all be correct while showing different numbers. Write a data dictionary before comparing them.

Label the fields you actually have

Field Unit and meaning to confirm Common mistaken comparison
Instantaneous power W or kW at a stated update time Treating it as a day’s energy
Interval-average power Average kW over the interval Treating it as the peak within that interval
Interval energy Wh or kWh during a stated interval Adding it to an overlapping daily total
Cumulative meter register Running total with reset or rollover rules Treating the displayed total as this month’s usage
Grid import/export Separate directions or a net figure Treating net grid exchange as all household consumption
Estimated cost Included tariff components and dates Expecting it to reproduce every bill charge

Work one interval example

A 2 kW interval-average reading over 15 minutes represents 0.5 kWh. It does not establish that demand stayed at 2 kW throughout. A 6 kW load for five minutes and no other use in that interval also averages 2 kW. These illustrative patterns have equal energy but different short-term demand.

If a file instead reports 0.5 kWh for the interval, do not multiply it by 0.25 again. Check the unit and whether the timestamp marks the start or end. Preserve missing, estimated or revised readings as such.

Match the boundary before reconciling totals

Align account, start and finish time, time zone and included equipment. A plug reading is usually already included in the home total, so adding the two double-counts that load. A detached building or subpanel may or may not be inside the consumer monitor’s measured boundary.

For solar, import and export are only part of the accounting. Production and any battery flows are needed to derive total consumption from the appropriate measurements. Use the solar measurement guide before interpreting lower imports as lower use.

Check what the utility actually publishes

The EIA smart-meter FAQ defines advanced metering infrastructure (AMI) as meters that “measure and record electricity usage at a minimum of hourly intervals and that provide the data to both the utility and the utility customer at least once a day.” By the EIA’s count, about 73% of U.S. residential electric meters were AMI meters in 2022. So a portal that adds hourly data once a day meets the EIA’s definition, and a meter’s capability does not guarantee that every customer portal provides the same resolution or delay. Ask the utility about available intervals, publication timing and estimated-data flags.

Download your smart meter data with Green Button

Green Button is an industry standard for exporting your own usage data from a utility’s website. The Department of Energy describes it as an industry-led effort to give utility customers “easy and secure access to their energy usage information in a consumer-friendly and computer-friendly format,” downloaded with “a simple click of a literal ‘Green Button’” on the utility’s website. It is built on the Energy Services Provider Interface (ESPI) standard from the North American Energy Standards Board, which DOE says has two parts: “a common XML format for energy usage information” and a protocol for transferring data to a third party “based on customer authorization.”

Those two parts are the two ways to get your data:

Download My Data Connect My Data
What happens You download your usage file to your own computer An app you authorize receives your data automatically
File format Standard Green Button XML; some utilities also offer CSV Standard Green Button data, fetched by the app
Your control You choose whether to pass the file on Opt-in consent; revocable at any time, per the Green Button Alliance
Typical use A spreadsheet check, a solar or contractor quote Ongoing tracking in a third-party app

Steps to download, using one utility as an example

Menu names differ between utilities, so treat these as a pattern rather than exact instructions for yours. San Diego Gas & Electric lists these steps:

  1. Log in to My Energy Center, the utility’s online account.
  2. Click the Usage tab.
  3. Choose Electric or Gas from the Meter menu above the graph.
  4. Click Green Button Download below the graph.
  5. Select the date range and file format.
  6. Click Download.

SDG&E requires a registered online account first, set up with the account number from a bill and the billing ZIP code. Con Edison, as another example, offers “up to one year of energy use data in a simple spreadsheet,” and precise usage data from your smart meter “either in a CSV or XML file.” If you can’t find the button, the Green Button Alliance runs a Green Button Directory that lists participating utilities; it says utilities “in nearly all 50 U.S. states” offer Green Button.

What the file contains

  • Interval length. DOE says Green Button data “can be provided in 15-minute, hourly, daily, or monthly intervals depending on what a utility decides to make available.” Green Button isn’t limited to smart meters; DOE notes it also covers utilities that can provide only monthly billing data.
  • History. It depends on the utility. SDG&E’s file holds “up to 13 months of Smart Meter energy usage data, for every hour or 15 minutes of every day.” Con Edison offers up to one year.
  • Fuel. At SDG&E, natural gas use is available only through Download My Data, while electricity is available through both options.
  • XML or CSV. The Green Button Alliance says utility CSV downloads “differ from site-to-site,” while Download My Data XML is “consistent across all energy-provider websites.” Choose XML if an app or service will read the file, and CSV if you plan to open it in a spreadsheet.

Once the file is open, apply the field checks at the top of this page: confirm whether each row is interval energy or average power, whether timestamps mark the start or the end of the interval, and which readings are estimated.

Before you share it with an app

DOE says customers must “first authenticate themselves on a utility portal with a login and password” before downloading, and that Connect My Data transfers “will happen only if a customer has granted explicit permission.” The Green Button Alliance adds that a Connect My Data authorization “is valid for an agreed-upon length of time and can be revoked at any time by the customer.” SDG&E advises customers not to give their account login to anyone else. Review the requested permissions before connecting a third party; the home energy monitor privacy checklist covers what to ask about accounts, copies and deletion.

Decide whether another monitor fills a real gap

Use existing utility information for broad account-level questions. Add a suitable plug meter for an appliance question, or qualified circuit monitoring for a defined hardwired-load question. The whole-home monitor versus portal comparison covers that purchase decision.

This guide defines measurement concepts and comparison checks. It does not validate a particular bill, inspect a customer export or establish consumer-monitor accuracy.

Sources

Green Button details were checked on October 9, 2026. Utility menus change; follow your own utility’s current instructions.