Your smart meter data shows when electricity was used, not just how much accumulated during the billing month. If an interval contains 1.80 kWh over 15 minutes, the average demand during that interval was 7.20 kW—not 1.80 kW and not necessarily the instantaneous peak. Start by checking the measurement unit, interval duration, and timestamp convention; those details determine whether your data can explain energy use, time-of-use charges, or billed demand.
Smart Meter Data: Which Reading Answers Which Question?
| Reading or data view | Key number or calculation | What it helps you decide | Conditions and limitations |
|---|---|---|---|
| Billing-period energy | Total kWh for the bill’s date range | Whether total electricity consumption increased or decreased | A monthly total does not identify when consumption occurred |
| 15-minute interval energy | Average kW = interval kWh ÷ 0.25 h | Which quarter-hours had the highest average load | Use this divisor only for an actual 15-minute energy interval; demand billing must follow your tariff’s measurement rules |
| Hourly interval energy | Average kW = interval kWh ÷ 1 h | Which hours used the most electricity | Hourly data cannot recover the highest 15-minute demand hidden inside an hour |
| Time-of-use energy | Sum of interval kWh within each tariff period | Whether moving a flexible load could reduce energy charges | Match timestamps to the applicable season, weekday, holiday, and local-time rules |
| Demand-billing data | Maximum qualifying interval demand, in kW | Whether overlapping loads contributed to demand charges | The qualifying interval and billing window come from the tariff; the highest visible reading is not automatically billed demand |
| Import, export, or net energy | Separate channels or a signed value, as defined by the utility | How grid purchases and exports changed | Confirm the direction and channel definition before adding values |
The U.S. Department of Energy explains that Green Button data may use 15-minute, hourly, daily, or monthly intervals, depending on the utility and available metering. Demand and energy charges also measure different things: energy charges use kWh, while demand charges use kW under the applicable billing rules.
What Your Smart Meter File Actually Contains
A useful interval record identifies a time period, a measured quantity, its unit, and the meter or service associated with it. Some downloads also include reading-quality information, separate import and export channels, or cost information. Green Button’s technical documentation distinguishes the measurement type, interval length, flow direction, unit, and scaling multiplier; a numeric value alone is not enough to interpret the record correctly. Before calculating anything, distinguish these three quantities:
- Interval energy, in kWh, is electricity used during a defined period.
- Average demand, in kW, is interval energy divided by that period’s duration in hours.
- A cumulative energy reading is a running register total, not the energy used in one interval. For cumulative readings, calculate the difference between successive readings before treating the result as interval energy. For an interval-energy export, do not take another difference between rows. Green Button identifies incremental interval data separately through its reading metadata.
Check Units and Scaling Before Importing XML
A spreadsheet-friendly export may already display kWh. Raw Green Button XML can instead contain an integer value, a base unit such as Wh, and a power-of-ten multiplier. The Green Button Alliance explains that the multiplier must be applied together with the unit to recover the intended measurement. For a record whose base unit is Wh:
[ E_{\text{kWh}}=\frac{\text{value}\times10^{m}}{1{,}000} ]
Here, (m) is the file’s powerOfTenMultiplier. For a hypothetical value of 1,800 with a multiplier of 0:
[ E=\frac{1{,}800\times10^0}{1{,}000}=1.80\text{ kWh} ]
Apply this conversion only when the metadata identifies Wh. Do not apply XML scaling again to a CSV column that the utility has already converted to kWh.
Download Your Data From the Utility
Use the utility account associated with the correct service address and electric meter. Downloading your own file and authorizing ongoing third-party access are different actions; Green Button provides both Download My Data and Connect My Data approaches. The following official instructions were checked for this 2026 guide. These are California utility examples, not a nationwide portal or a guarantee that every customer receives the same interval resolution.
| Utility and service area | Official entry point | Published download path | Interval information |
|---|---|---|---|
| PG&E, California service territory | Energy Usage Tools | Sign in → Usage and rates → Bill period usage → View Usage Details → Green Button Download my data | The customer usage-tools page lists downloadable 15-minute electric data. |
| SDG&E, California service territory | Download My Green Button Data | Sign in to My Energy Center → Usage → select Electric in the Meter menu → Green Button Download → choose dates and format | SDG&E describes hourly or 15-minute records and up to 13 months of history. |
PG&E’s separate Share My Data documentation describes generally hourly residential data and 15-minute commercial data. Because published guidance differs by access channel and customer, inspect the duration in your actual download rather than assuming that every PG&E export is quarter-hourly. For another utility, locate its official usage-data or Green Button page through your account portal. Export the exact billing period when checking a bill; use a longer available history when comparing seasonal patterns or rate options. A short sample can explain one event without representing the entire year.
Read a Daily Load Profile Without Mistaking It for a Benchmark
A load profile shows how consumption changes over time. Low overnight use can help establish a comparison baseline, while larger daytime or evening intervals can identify periods worth investigating. The profile narrows the timing of an event; it does not, by itself, identify which appliance caused it. The following table is a hypothetical training example for one complete 24-hour day. It assumes interval energy has already been converted to kWh and grouped into the time blocks shown. It is not measured customer data, a national average, or a recommended operating target.
| Local-time block | Duration | Energy used | Average demand | Interpretation to investigate |
|---|---|---|---|---|
| 12:00–6:00 a.m. |
| 6 h | 1.80 kWh | 0.30 kW | Overnight baseline |
|---|---|---|---|
| 6:00–9:00 a.m. |
| 3 h | 3.60 kWh | 1.20 kW | Morning activity |
|---|---|---|---|
| 9:00 a.m.–4:00 p.m. |
| 7 h | 2.80 kWh | 0.40 kW | Lower daytime activity |
|---|---|---|---|
| 4:00–9:00 p.m. |
| 5 h | 8.00 kWh | 1.60 kW | Evening load overlap | |
|---|---|---|---|---|
| 9:00 p.m.–midnight | 3 h | 1.20 kWh | 0.40 kW | Return toward baseline |
| Full day | 24 h | 17.40 kWh | 0.725 kW | Daily total and average, not peak demand |
Each block uses the same calculation:
[ P_{\text{avg}}=\frac{E}{t} ]
For the evening block:
[ P_{\text{avg}}=\frac{8.00\text{ kWh}}{5\text{ h}}=1.60\text{ kW} ]
Grouping helps you see broad patterns, but it hides shorter peaks. Keep the original interval rows when investigating demand; a five-hour average cannot identify the highest quarter-hour within that block.
Calculate the Highest 15-Minute Average Demand
Use the original interval-energy file, not an hourly or daily summary. The demand calculation divides energy by interval duration; a utility’s demand interval is commonly 15 or 30 minutes, but the applicable tariff determines the relevant period.
Inputs and Assumptions
This hypothetical excerpt uses four consecutive 15-minute intervals within the evening block above. Values are imported energy in kWh, timestamps label interval starts, and there are no missing rows in this one-hour excerpt.
| Interval start | Interval duration | Interval energy | Calculated average demand |
|---|---|---|---|
| 6:00 p.m. |
| 15 min | 0.20 kWh | 0.80 kW |
|---|---|---|
| 6:15 p.m. |
| 15 min | 0.30 kWh | 1.20 kW |
|---|---|---|
| 6:30 p.m. |
| 15 min | 1.80 kWh | 7.20 kW |
|---|---|---|
| 6:45 p.m. |
| 15 min | 0.40 kWh | 1.60 kW |
Calculation Process
1. Confirm that each value represents interval energy in kWh.
- Convert the interval duration to hours.
- Divide each row’s energy by its duration.
- Find the largest calculated average demand.
- Preserve the corresponding timestamp so you can compare it with operating schedules and tariff windows. For the 6:30–6:45 p.m. interval:
[ t=\frac{15}{60}=0.25\text{ h} ]
[ P_{\text{avg}}=\frac{1.80\text{ kWh}}{0.25\text{ h}}=7.20\text{ kW} ]
The highest 15-minute average in this excerpt is 7.20 kW. This calculation does not establish the peak for the full billing period; that requires all qualifying intervals. You can use the site’s kWh converter as a companion unit-conversion check. Keep the interval-duration calculation above explicit so the result remains independently reproducible.
Why Hourly Data Can Hide the Peak
The four interval-energy values total:
[ E_{\text{hour}}=0.20+0.30+1.80+0.40=2.70\text{ kWh} ]
The one-hour average is therefore:
[ P_{\text{hour}}=\frac{2.70\text{ kWh}}{1\text{ h}}=2.70\text{ kW} ]
That hourly average is much lower than the excerpt’s 7.20 kW quarter-hour average. If all you have is 2.70 kWh for the hour, you cannot reconstruct the four underlying quarter-hour demands: many different load patterns could produce the same hourly total.
A 15-minute average is not an instantaneous maximum. It cannot reveal a brief motor-starting surge or establish conductor, breaker, or service sizing. Use interval data for energy and billing analysis, not as a substitute for applicable NEC requirements, local AHJ requirements, manufacturer instructions, or a site-specific electrical assessment.
Connect Interval Data to Your Rate Plan
Interval data becomes useful for cost decisions only when it is paired with the rate schedule applicable to your account and billing dates. A high-use interval may be expensive under a time-of-use plan, relevant to a demand charge, both, or neither. SCE’s business billing explanation separates energy charges, overall demand charges, and demand charges tied to particular time-of-use periods.
| Rate structure | Calculation to perform | What changing load timing can accomplish |
|---|---|---|
| Flat energy rate | Total kWh × applicable USD/kWh rate | Timing alone does not change the energy charge when the rate and total kWh remain unchanged |
| Time-of-use energy rate | Sum of interval kWh × the applicable USD/kWh rate for each period | Moving flexible consumption to a lower-priced period may reduce energy charges |
| Demand-based rate | Apply each demand component’s qualifying kW and USD/kW rate | Reducing overlapping loads may lower qualifying peak demand |
| Energy plus demand charges | Calculate energy and demand components separately | A lower energy charge does not necessarily mean a lower total bill |
These are calculation structures, not local price estimates. Use your utility’s effective tariff rather than a national average or another customer’s rate. For a concrete California example, SCE’s 2026 TOU-GS-3 fact sheet distinguishes facilities-related demand based on monthly maximum demand from time-related demand within specified periods. It also describes an Option DD with different demand treatment, demonstrating why a single “highest kW × rate” calculation may not reproduce every bill. The fact sheet explicitly directs customers to CPUC-approved tariffs for complete pricing and conditions. Do not treat an interval-energy calculation as the full invoice. Include applicable fixed charges, separate supply and delivery components, demand charges, taxes, adjustments, and export credits when reconciling the bill.
Reconcile the Download With Your Bill
Reconciliation checks whether you are analyzing the right records before making an operating or rate decision.
1. Match the service address, meter or service identifier, and billing dates.
- Check whether timestamps identify interval starts or interval ends.
- Confirm the time zone and daylight-saving treatment before assigning tariff periods.
- Sum interval energy within the billing boundaries.
- Compare the result with the corresponding billed energy quantity.
- Investigate missing records, duplicated imports, estimated readings, unit scaling, and import/export treatment before calculating savings.
- Calculate billed demand separately using the tariff’s qualifying interval and windows. For solar customers, PG&E provides a separate Detail of Bill view for applicable net-energy-metering accounts. Its documentation describes grid energy and time-of-use information, reinforcing the need to compare the correct billing quantity rather than treating every energy channel as interchangeable.
Do not replace a missing interval with zero unless the utility confirms zero consumption. Do not delete a repeated local-time row solely because its clock label matches another row: first check the date, time-zone offset, interval boundaries, and daylight-saving convention. If totals differ, resolve the cause before using the file to justify a rate change or a claimed reduction. A spreadsheet result is an analytical estimate, not a utility-approved bill adjustment or a savings guarantee.
Smart Meter Data Self-Check
Use this checklist before relying on your analysis:
- Verify that the file covers the correct service and billing period.
- Confirm whether values are interval kWh, average kW, or cumulative readings.
- Read interval durations from the file or documentation rather than assuming 15 minutes.
- Check units and any XML scaling multiplier.
- Confirm timestamp start/end labeling, time zone, and daylight-saving treatment.
- Investigate missing, duplicated, or estimated records.
- Keep import, export, and net-energy channels distinct.
- Retain original-resolution data when calculating interval peaks.
- Apply the rate schedule effective for the account and dates being analyzed.
- Compare billing quantities before drawing cost conclusions.
- Keep billing analysis separate from electrical design, permitting, and equipment-sizing decisions.