Residential Service — Voltage Monitoring Report

Generated 2026-07-24 16:50:48 · Continuous monitoring since 2026-06-29 20:49:29 · 1,962,742 samples recorded

Measurement Method

Three calibrated energy meters, each on a separate 120 V branch circuit, spanning both legs (Leg A and Leg B) of the split-phase service.
One 240 V line reference measuring line-to-line voltage and grid frequency.
Sampled continuously every 1–2 seconds since 2026-06-29 20:49:29.
Legs measured independently; Leg A + Leg B cross-checks against the 240 V line reference.

Worst Recorded Events

Leg imbalance: Leg A 101.8 V and Leg B 122.8 V simultaneously — a 21.1 V imbalance — on 2026-07-23 08:31:29

Whole-service sag: the 240 V line voltage dropped to 220.2 V (2026-07-02 22:34:32) — both legs sagging together, distinct from the leg-to-leg imbalance.

Key Findings (measured)

Leg-imbalance events (≥3 V)582

Major events (≥8 V)34

Lowest single-leg voltage101.8 V (2026-07-23 08:31:27)

Highest single-leg voltage130.1 V (2026-07-24 12:36:39)

240 V line range220.2–246.6 V (nominal 240)

Grid frequency range59.783–60.017 Hz (normal)

What the Data Shows

The two 120 V legs move in opposite directions — one sags sharply while the other rises — the leg-to-leg imbalance.
Separately, at times the 240 V line voltage itself drops (both legs sagging together, down to ~220.2 V) — indicating a voltage drop across the service under load, not only a neutral imbalance.
Grid frequency remained normal (~60 Hz) throughout, indicating the variation originates in the local service, not the wider grid.
Events are concentrated in evening and overnight hours and largely absent midday (see timing below).
Peak imbalance has increased over the monitoring period (see daily trend).

Daily Worst Imbalance (trend)

Date	Worst leg imbalance
2026-06-29	4.8 V
2026-06-30	14.0 V
2026-07-01	11.7 V
2026-07-02	16.8 V
2026-07-03	17.6 V
2026-07-04	5.2 V
2026-07-05	15.9 V
2026-07-08	3.4 V
2026-07-10	4.8 V
2026-07-11	4.4 V
2026-07-12	8.4 V
2026-07-13	7.9 V
2026-07-14	7.2 V
2026-07-15	6.4 V
2026-07-16	5.6 V
2026-07-17	6.2 V
2026-07-18	3.5 V
2026-07-19	3.7 V
2026-07-20	7.4 V
2026-07-21	6.8 V
2026-07-22	4.9 V
2026-07-23	21.1 V
2026-07-24	6.6 V

Timing — Events by Hour of Day

00:00	30
01:00
02:00	1
03:00	2
04:00	2
05:00	4
06:00	1
07:00
08:00	36
09:00	10
10:00	4
11:00	3
12:00	19
13:00	4
14:00	6
15:00	15
16:00	63
17:00	78
18:00	37
19:00	140
20:00	23
21:00	20
22:00	62
23:00	22

Recorded Major Events (≥8 V imbalance)

Timestamp	Leg A	Leg B	Imbalance	Low leg	240V line
2026-07-23 17:55:48	104.4 V	123.4 V	19.0 V	Leg A	224.9 V
2026-07-23 09:18:42	108.0 V	123.1 V	15.1 V	Leg A	226.2 V
2026-07-23 08:48:45	112.9 V	123.2 V	10.3 V	Leg A	239.7 V
2026-07-23 08:31:29	101.8 V	122.8 V	21.1 V	Leg A	225.1 V
2026-07-23 05:37:57	108.1 V	122.2 V	14.1 V	Leg A	236.3 V
2026-07-23 05:21:10	113.0 V	122.6 V	9.7 V	Leg A	237.3 V
2026-07-23 04:55:45	107.4 V	122.2 V	14.8 V	Leg A	228.5 V
2026-07-23 03:24:52	106.9 V	122.6 V	15.7 V	Leg A	230.9 V
2026-07-12 22:00:27	122.3 V	113.9 V	8.4 V	Leg B	236.0 V
2026-07-05 20:19:01	104.7 V	120.5 V	15.9 V	Leg A	225.6 V
2026-07-05 20:18:34	110.9 V	120.4 V	9.5 V	Leg A	228.5 V
2026-07-05 19:35:32	107.5 V	120.5 V	13.0 V	Leg A	229.7 V
2026-07-05 17:43:01	112.5 V	121.4 V	9.0 V	Leg A	—
2026-07-03 05:49:53	106.8 V	120.8 V	14.0 V	Leg A	231.6 V
2026-07-03 00:41:36	103.2 V	120.7 V	17.6 V	Leg A	226.4 V
2026-07-02 23:41:17	105.1 V	121.9 V	16.8 V	Leg A	233.7 V
2026-07-02 23:00:24	104.2 V	121.1 V	16.8 V	Leg A	225.7 V
2026-07-02 22:50:13	110.5 V	121.0 V	10.5 V	Leg A	234.9 V
2026-07-02 22:38:14	104.5 V	120.8 V	16.2 V	Leg A	228.6 V
2026-07-02 22:34:33	104.2 V	120.9 V	16.7 V	Leg A	220.3 V
2026-07-02 22:29:54	112.5 V	120.7 V	8.2 V	Leg A	228.4 V
2026-07-02 22:22:27	106.2 V	120.6 V	14.4 V	Leg A	230.0 V
2026-07-02 22:17:28	105.6 V	120.6 V	15.1 V	Leg A	230.5 V
2026-07-02 20:40:00	111.8 V	121.0 V	9.2 V	Leg A	232.8 V
2026-07-02 20:09:33	108.6 V	120.4 V	11.8 V	Leg A	231.8 V
2026-07-02 19:52:17	108.8 V	120.6 V	11.8 V	Leg A	231.6 V
2026-07-02 18:36:26	106.5 V	121.7 V	15.1 V	Leg A	224.4 V
2026-07-02 10:22:01	113.0 V	123.2 V	10.2 V	Leg A	231.2 V
2026-07-01 19:16:32	108.6 V	120.2 V	11.7 V	Leg A	232.0 V
2026-06-30 08:57:35	110.6 V	120.0 V	9.4 V	Leg A	—
2026-06-30 08:54:04	110.3 V	121.5 V	11.2 V	Leg A	—
2026-06-30 08:52:56	113.5 V	121.6 V	8.1 V	Leg A	—
2026-06-30 08:52:24	107.1 V	121.0 V	14.0 V	Leg A	—
2026-06-30 08:52:02	109.2 V	121.0 V	11.8 V	Leg A	—

Measured at the point of use with calibrated metering; values are RMS voltages sampled at 1–2 second intervals. Leg A and Leg B are independent 120 V measurements; their opposite-direction movement summing to a constant ~240 V is characteristic of a shared-neutral / service-side condition.