ED wait times at California hospitals: what CMS's timing measures show

What do CMS's ED timing measures count?

Each one is the median number of minutes from a patient's arrival in the ED to the patient's departure, for patients who were not admitted to the hospital. There are four versions, one for each group of patients, and CMS adds a fifth measure for patients who left before anyone saw them.

CMS's files and Care Compare call these times averages, but they are medians. CMS's data dictionary says hospital data are "reported in median time only", and that the median "is often referred to as the 'average time'" for readers. About half of a hospital's patients in each group spent longer than its figure.

None of the four OP-18 measures counts a patient who was admitted. CMS's measure of boarding was ED-2, the median time from the decision to admit a patient to the patient's departure from the ED. CMS retired its data collection, and the data dictionary says ED-2 was removed "beginning with the October 2025 release." Since then, Care Compare has shown no boarding time for any hospital.

How does California compare with other states?

California's 174 minutes for patients sent home is longer than 38 states and shorter than 11 states and DC. The median of the 50 states and DC is 151 minutes, by Kent Applied's count. North Dakota had the shortest figure, 110 minutes, and DC the longest, 303.

These state and national figures are CMS's own. According to CMS's footnotes, its state and national figures for OP-18b and OP-22 include Veterans Health Administration and Department of Defense hospitals, and its OP-18c figures include Veterans Health Administration hospitals. CMS does not say in the files or the data dictionary how it combines hospitals into a state figure, so this report uses the figures as CMS prints them. California's 174 minutes happens to equal the median of its own 267 hospitals, while the national 162 minutes is above the median hospital in the country, at 148.

Are California's ED times longer at every size of ED?

No. Within each of CMS's ED volume groups, California's figure for patients sent home is close to the national one or below it, except at the smallest EDs. CMS puts each hospital that reported its 2024 ED volume (its EDV measure) in one of four groups, and publishes OP-18b for each group by state.

• Low volume: 144 minutes in California, against 123 nationally.
• Medium volume: 158 minutes, against 165.
• High volume: 192 minutes, against 202.
• Very high volume: 203 minutes, against 201.

California also has more of its EDs in the biggest group. Of the 259 California hospitals that CMS places in a volume group, 88 (34%) are in the very high volume group, against 703 of 3,826 hospitals nationally (18%). In California, each larger group has a longer time than the one below it. Nationally the same holds up to the high volume group, and the high and very high groups are about even, at 202 and 201 minutes.

The mix of ED sizes could account for most of the 12-minute gap between California and the nation, by a rough check. If each of CMS's national group figures is weighted by the number of California hospitals with a reported time in that group, the result is 175.6 minutes, close to California's 174. Weighting California's group figures by the national mix of hospitals gives 165.4 minutes, close to the national 162. The check is rough because it counts hospitals rather than patients, and medians do not add up exactly; CMS does not say how it combines hospitals into a state figure, so an exact answer cannot be worked out from its files.

How much do California hospitals differ from one another?

By hours, even among hospitals of the same size. The 267 California hospitals with a reported time for patients sent home ran from 69 to 413 minutes, and the middle half sat between 146.5 and 208.5 minutes. Thirty-three of them had a median above 240 minutes, or 4 hours.

The spread holds within each volume group. Among very high volume EDs, the middle California hospital's time was 199.5 minutes and the range ran from 139 to 413. Among low volume EDs, the middle hospital's time was 139.5 minutes and the range ran from 74 to 322.

CMS shows 62 of the 329 California hospitals as "Not Available" for OP-18b. For 50 of them, CMS's footnote says "Results are not available for this reporting period," and for 12 it says "Data are shown only for hospitals that participate in the Inpatient Quality Reporting (IQR) and Outpatient Quality Reporting (OQR) programs."

A longer time tells a reader how long patients stayed in the ED. It does not show why, or whether their care was worse, and this report makes no claim about either.

How long do patients wait in a California ED before a transfer?

Patients transferred from a California ED to another facility spent a median of 398 minutes in the ED first, against 287 minutes nationally (OP-18d). Of the 50 states and DC, five states and DC had a longer figure.

The other groups are closer to the national figures. Psychiatric or mental health patients who were not admitted spent 260 minutes in California's EDs, against 257 nationally (OP-18c), and all patients not admitted spent 180 minutes, against 168 (OP-18a).

The transfer figure rests on fewer hospitals than the others. Only 102 of the 329 California hospitals have a reported OP-18d time; for 156 more, CMS's footnote says "The number of cases/patients is too few to report." Among the 102, the times ran from 170 to 917 minutes, and the middle hospital's was 405. The state figure of 398 minutes comes with no list of the hospitals whose patients it includes.

Do more patients leave before being seen where ED times are longer?

In 2024, 2% of ED patients in California left before being seen, the same share as nationally (OP-22). Among California hospitals, the share ran from 0% to 13%.

California hospitals with longer times for patients sent home tended to have more patients leave unseen. Across the 259 hospitals with both measures, the rank correlation (Spearman) was 0.37, where 1 would mean the two measures rank the hospitals in the same order and 0 would mean no link between the two rankings. The two measures also cover different periods: OP-22 covers 2024, and OP-18b covers October 2024 to September 2025. A link between two measures says nothing about cause.

What replaces these measures, and when?

CMS's CY 2026 outpatient payment final rule, published November 25, 2025, adopted the Emergency Care Access & Timeliness measure for hospital outpatient departments. Reporting is voluntary for 2027 and mandatory from 2028. The same rule removes the median time for discharged ED patients and Left Without Being Seen from the 2028 reporting period. Care Compare reports those two as OP-18b and OP-22, and it splits the median time into the four groups of patients, OP-18a to OP-18d. The rule removes the measure as a whole and does not discuss the four groups one by one.

The new measure counts the share of ED visits with any of four problems, as the rule lists them: a wait of more than 1 hour from arrival to a treatment room, a patient who left without being evaluated, boarding of more than 4 hours from the decision to admit to leaving the ED, and an ED stay of more than 8 hours. So boarding returns to a public CMS measure, as a share of visits over 4 hours rather than a median time, once the 2028 data are published. It is an electronic clinical quality measure, calculated from the hospital's electronic health record.

CMS will not publish the voluntary 2027 data. The rule says CMS "will begin to publicly report these data beginning with the first mandatory reporting period," which is calendar 2028, and it gives hospitals until "the submission deadline for the CY 2028 data in May 2029." The rule sets no date for publishing. The reporting requirement belongs to CMS's Hospital Outpatient Quality Reporting program, which the rule calls "a pay-for-reporting program that penalizes hospitals for not submitting data," so it applies to hospitals in that program rather than to every hospital.

For its inpatient quality programs, CMS asked for comments on using the measure in its FY 2027 inpatient payment proposed rule of April 14, 2026, and the final rule of August 4, 2026 adopted nothing. The CY 2027 outpatient proposed rule of July 7, 2026 describes 2028 as "the first year that submitting four quarters of data for this measure is mandatory." The CY 2027 outpatient final rule had not been published in the Federal Register as of October 20, 2026.

Boarding itself is the subject of ED boarding starts with inpatient capacity, and the delays on the inpatient side that hold beds are in discharge delays at 52 hospitals in one quarter.

What can a hospital do with these numbers?

Start by comparing a hospital's own times with the middle California hospital in its CMS volume group, which the explorer shows for each measure. Then check the measures CMS shows as "Not available" and the footnote that gives the reason, because a measure with no public number is a gap a reader of Care Compare will see too.

For the measure that replaces these, the 4-hour boarding threshold counts the time from the decision to admit a patient to the patient leaving the ED, which is the wait for an inpatient bed. Kent Applied's Throughput Diagnostic finds the one step causing your discharge delays, ED boarding or OR backlog, and puts a dollar cost on each day of delay. It takes 3 weeks, for $14,500.

How we did this

Kent Applied downloaded CMS's Timely and Effective Care files for hospitals, states and the nation on October 20, 2026. CMS last modified the hospital file on July 22, 2026, and its data dictionary for this release is dated July 2026. We kept every California row for the ED measures: OP-18a to OP-18d for October 1, 2024 to September 30, 2025, and OP-22 and the ED volume group for 2024. That gives 329 California hospitals, each joined to its hospital type in CMS's Hospital General Information file.

Every hospital's number is CMS's as printed. Where CMS shows "Not Available", the table shows the same, with CMS's footnote number and its text from CMS's footnote crosswalk, never a zero. Ten hospitals' OP-18b times carry CMS's footnote 3, "Results are based on a shorter time period than required," and stay in. CMS's general information file lists 30 of the hospitals with an OP-18b time as having no emergency services; their times also stay as CMS printed them.

State and national figures are CMS's own, never recomputed. Kent Applied computed the rest from CMS's hospital file: the counts of hospitals, the median, quartiles and range of California hospitals' times, how many of the 50 states and DC have a longer figure than California, the share of hospitals in each volume group, the middle California hospital in each group for each measure, and the Spearman rank correlation between OP-18b and OP-22. Quartiles use the inclusive method, so the middle half runs from the 25th to the 75th percentile of the hospitals' own values. Rankings and medians of states use the 50 states and DC; Puerto Rico and the other territories in CMS's file stay in its national figure and in the state download, and the map leaves them off.

The dot chart of California hospitals leaves off 8 critical access hospitals that have an OP-18b time but no ED volume group, including the 69-minute hospital, so its range starts at 74 minutes. CMS's hospital file also has a "Sample" column for OP-18b and OP-22. The data dictionary does not define it, so the report does not use it, and the download carries it as printed.

The report shows each hospital by a number rather than its name. Numbers run from the shortest OP-18b time to the longest, and the 62 hospitals with no OP-18b time come last.

The two periods differ. The ED times cover October 2024 to September 2025, and OP-22 and the volume groups cover calendar 2024.

Questions and answers

Is OP-18b the time until a patient sees a doctor?

No. OP-18b runs from a patient's arrival in the ED to the patient's departure, for patients sent home. The wait for a treatment room is one of the four parts of the Emergency Care Access & Timeliness measure, which counts a wait of more than 1 hour, and hospitals in CMS's outpatient quality reporting program must report it from 2028.

Why does a hospital show "Not available"?

Each one carries a footnote from CMS that gives the reason. For OP-18b in California, 50 hospitals carry footnote 5, "Results are not available for this reporting period," and 12 carry footnote 19, which says CMS shows data only for hospitals that take part in its inpatient and outpatient quality reporting programs. The transfer time is missing more often, mostly with footnote 1, "The number of cases/patients is too few to report."

Do CMS's California figures include VA and military hospitals?

Yes for OP-18b and OP-22: CMS's footnotes say its state and national figures for those measures include Veterans Health Administration and Department of Defense hospital data. Its OP-18c figures include Veterans Health Administration data, and its files say nothing either way for OP-18a and OP-18d. The hospital file, and so the explorer, holds the 5 Defense Department hospitals in California but no VA hospitals, which CMS publishes in a separate file.

When will these numbers change?

The OP-18 times are refreshed every quarter, and OP-22 and the ED volume groups once a year, according to CMS's data dictionary. Hospitals in CMS's outpatient quality reporting program stop reporting OP-18b and OP-22 with the 2028 reporting period, when the Emergency Care Access & Timeliness measure becomes mandatory.

Where is the data?

The explorer above lists every California hospital in CMS's file, and the two downloads hold the hospital table and CMS's state figures. CMS's figures are in the public domain, and Kent Applied's tables and labels are free to reuse with credit under CC BY 4.0.