When the grid failed
- The battery gateway records the moment my house stops drawing from the utility and starts to run on its own.
- Since the system was energized on 8 November 2024, that happened 17 times in 24 months: 16 grid failures and 1 intentional off-grid test.
- The longest grid failure kept the house islanded for 9 minutes, including the 5-minute hold. The utility itself was out for about 4 minutes of it.
- The headline number is not the one you would expect.
- The house spent 96 minutes disconnected from the grid, and 93 minutes of it in grid failures.
- But most of that is a delay the inverter must observe before it reconnects. The utility was not absent then.
- Take the delay out of the grid failures, and leave the test out.
- Then the grid itself was down for about 13 minutes.
- This control zooms the charts that have a date axis. Totals are for the full record.
utility out
reconnect hold, computed
17 interruptions in 24 months
- Each mark is one time the house went to battery. Its height is how long it stayed there.
- The pale part of every mark is the five minutes the inverter must wait once the grid is back.
- So only the solid part is the time the utility was out.
- 9 of these marks have no solid part at all.
No grid failure ends before the five-minute hold, to within 3 seconds
- IEEE 1547 clause 4.10 sets an Enter Service delay: the inverter watches five minutes of healthy grid before it reconnects.
- New York's Department of Public Service publishes 300 s as the required default.
- The floor shows without a label. The shortest grid failure lasted 299.9 seconds.
- That is within the 3 seconds of jitter the gateway's edges carry.
- Only the single intentional off-grid test is below it. No anti-islanding rule governs that test.
When they happen
- Hour of the day runs across, and month runs down.
- A run is failures that each began within 3 hours of the one before.
- A run of two came within 9 minutes, from 14:22 on 13 May 2026.
- A run of three came within 61 minutes, from 15:54 on 2 July 2026.
- A run of two came within 6 minutes, from 02:30 on 6 July 2026.
- A run of two came within 43 minutes, from 23:20 on 13 August 2026.
What the weather was doing
- Every hour on record is a pale dot. The hours that hold an outage are marked.
- Hover for each one's rank against hours from the same fortnight and time of day. A rank against all hours would only say that July afternoons are warm.
- The two failures from 13 May 2026 began at 67 and 67°F, with gusts of 4 and 6 mph.
- The three failures from 2 July 2026 began at 93, 89 and 88°F, with gusts of 0, 1 and 4 mph.
- The two failures from 6 July 2026 began at 70 and 70°F, with gusts of 0 and 0 mph.
- The highest gust against comparable hours came on 4 April 2026: 10 mph, at 57°F.
- That gust is at or above 98% of hours from the same fortnight and time of day.
- A percentile says an hour was unusual for the season, not that conditions were extreme. The dashed lines mark absolute thresholds.
- The station is in the garden, so this is the weather at my house, not at an airport.
grid
solar
battery
house
Each one, close up
- Twenty minutes either side: each trace shows that much time before and after its outage.
- Grid power drops to exactly zero and then stops being written at all.
- Home Assistant records on change, and a steady value produces no rows.
- The gap in the line is the outage. The battery supplies the house throughout.