How to Run a Whole-House Baseline Test at the Electric Meter

Why this matters

A customer says the house "isn't doing anything different" and the bill keeps climbing. Half the time the answer is a load that never shuts off: a dehumidifier set to continuous, a heat cable left plugged in since February, a second freezer in the shed. You can argue about it for an hour, or you can stand at the meter for twenty minutes and watch the house tell you. The baseline test turns the electric meter into a single instrument that reads the whole house, then uses the panel to split that reading circuit by circuit until the constant load has nowhere to hide.

It is also the test most often done badly. A reading taken while the refrigerator happened to be running, a breaker flipped without asking about the oxygen concentrator, a meter constant misread by a factor of ten. The steps below are ordered so each one protects the reading that follows it.

What you need and what you never touch

• A stopwatch (a phone is fine) and a notepad or the job record.
• The meter's faceplate constant, printed on the meter. On an electromechanical meter it is Kh, the watt-hours per revolution of the disk. On a digital meter it is usually the watt-hours per pulse of a small blinking indicator, sometimes labeled Kh as well, and many digital meters also scroll an instantaneous demand reading in kW.
• The customer's permission, in words, before any breaker moves.

The meter, its seal and the meter base belong to the utility. You read the meter; you never open it, pull it, or cut the seal, because that is tampering in most service territories and the meter base holds unfused service conductors. The panel's dead front (the inner cover with the breaker handles poking through) stays on. Operating a breaker handle with the dead front in place is ordinary use; removing the dead front is electrical work for a qualified person. If you see scorching, smell hot insulation, hear buzzing, find water in or on the panel, or a breaker is hot to the touch, stop the test there and route it to a licensed electrician.

Step 1: Read the meter with the house running normally

Before anything is switched off, time the disk or the pulse light. Count the seconds for one full revolution (the black mark on the disk edge passing the front) or between two pulses. If the disk is fast, time five revolutions and divide.

The arithmetic is the same for both meter types:

watts = Kh x 3,600 / seconds per revolution (or per pulse)

The 3,600 converts watt-hours to watt-seconds. With Kh 7.2 and one revolution in 12 seconds, the house is drawing 7.2 x 3,600 / 12 = 2,160 W at that moment. Check it the other way: 2,160 W for 12 seconds is 25,920 watt-seconds, divided by 3,600 is 7.2 Wh, one revolution. If a digital meter shows instantaneous kW, write that down too, and expect it to agree with your timed number within the meter's display rounding.

Why first: this is your sanity check on the constant. If the house is plainly busy (dryer running, AC on) and you compute 216 W, you misread the Kh or miscounted, and every later reading would be wrong by the same factor. Skip this and you can spend an hour chasing a load that exists only in a decimal point.

Step 2: Agree which loads go off, and which stay on

Walk the house with the customer and list what will be switched off at the device: HVAC at the thermostat (set to Off, not just turned down), water heater, dryer, dishwasher, pool or spa equipment, EV charger, lights, TVs. Then ask the questions that change the plan:

• Is anything medical or life-safety on a plug? An oxygen concentrator, a CPAP in use, a powered lift, a sump pump during wet weather, a fire alarm or security panel monitored offsite. These stay on and you work around them.
• Is the well pump or a sump pump on its own breaker? Switching off a sump pump in a storm is how a bill call turns into a flooded basement.
• Anything that loses data or resets? Computers mid-task, irrigation and pool timers, a programmed oven clock. Say what will need resetting before you cause it.

What breaks if skipped: the test ends early because someone panics about a beeping alarm panel, or worse, a protective load sits off for twenty minutes without anyone deciding it could.

Step 3: Switch off known loads and read what remains

With everything on the list off at the device, wait a couple of minutes so any compressor finishes coasting down, then time the meter again. Take two readings a minute or so apart. Two readings, not one, because the refrigerator, a chest freezer and a dehumidifier all cycle on their own thermostats. If the two readings agree closely, you have a stable floor. If one is much lower, a cycling appliance just shut off; wait and take a third.

This remaining draw is the house baseline: everything that runs when the occupants are asleep. A normal baseline is made of small things that are supposed to be on: the refrigerator when its compressor runs, a modem and router, the furnace or air handler control transformer, smoke and CO alarms, a security panel, TVs and audio gear in standby, a doorbell transformer, smart speakers, chargers left in the wall, a garage door opener. In kind, a healthy baseline is a collection of small loads plus whatever refrigeration happens to be running. What does not belong in it is a single large, steady draw that nobody can name.

Why the HVAC goes off at the thermostat and not the breaker: setting the thermostat to Off lets the equipment finish its own shutdown and keeps the compressor's restart delay in charge when it comes back on. A breaker flipped under a running compressor and closed again a minute later can restart it against high pressure.

Step 4: Switch breakers one at a time and read after each

Now the panel. Stand to the side of the panel rather than square in front of it, use one hand, and turn one breaker off. Time the meter. Turn that breaker back on before moving to the next. One at a time, back on before the next, every time.

Why one at a time and not all off then back on: turning everything off and then restoring breakers one by one sounds faster, but it puts every load in the house through a simultaneous restart, and you lose the clean comparison. With one breaker off, the drop in the reading is exactly what that circuit was carrying.

Why back on immediately: a breaker left off by accident is the most common way this test causes a callback. The freezer in the garage thaws, the sump pump never restarts, and the customer's next bill call is about a different problem you caused.

Skip the breakers already accounted for (the dryer, range and water heater breakers serve loads you already turned off at the device), and log every reading as you go. Here is a real log, Kh 7.2, house baseline from Step 3 at 30 seconds per revolution (864 W), confirmed by a second read at 31 seconds (836 W):

BREAKER LOG   Kh 7.2   floor 30 s/rev = 864 W
------------------------------------------------
brkr  label              s/rev   watts   drop
 1    kitchen recep        31     836     28
 3    living rm / hall     30     864      0
 5    bedrooms             31     836     28
 7    furnace / air hdlr   31     836     28
 9    bath GFCI            30     864      0
14    garage / basement    90     288    576
16    exterior / porch     30     864      0
------------------------------------------------
drop = 864 minus watts with breaker off
breaker 14 back on: 30 s/rev, 864 W again

Notice the 28 W drops on breakers 1, 5 and 7. They are not loads. At this disk speed, one second of stopwatch error is 864 minus 836, which is 28 W, so anything that small is timing noise. Treat a drop as real only when it is several seconds of revolution time and repeats when you re-read. If the floor suddenly falls and stays down on a breaker that should not matter, a cycling appliance such as the refrigerator just shut off; re-read the floor before blaming that circuit.

Breaker 14 is the finding. Turning it off moved the disk from 30 seconds to 90 seconds per revolution: 7.2 x 3,600 / 90 = 288 W remaining, so the circuit was carrying 864 minus 288, which is 576 W, steady.

Step 5: Walk the circuit and find the load

A breaker narrows it to a circuit; the circuit label narrows it to rooms. On this job the garage and basement circuit fed eleven receptacles. With breaker 14 on, the tech and the customer walked them. In the basement, a dehumidifier sat with its humidistat turned to continuous run, bucket draining to a floor drain, running since the spring the basement flooded. The customer had forgotten it was there because it was behind the furnace.

To confirm, unplug the suspected load and time the meter again. The disk went back to 89 seconds per revolution (291 W), within a second of the breaker-off reading. That agreement is your confirmation: the whole 576 W on that circuit was the one appliance. If unplugging the suspect had only recovered half the drop, there would be a second load on the circuit still to find.

What it means for the bill, carried in kWh so it holds at any rate:

• 576 W running 24 hours is 0.576 kW x 24 h = 13.8 kWh per day.
• Over a 30-day billing period, 0.576 kW x 720 h = 414.7 kWh.
• Cost is that figure times the rate per kWh printed on the bill, plus any tier effect if the house sits near a tier boundary.

Check against the bill before saying anything: if the customer's bills run around 1,100 kWh a month, 415 of them being one forgotten appliance is a big share and plausible. If the bills run 400 kWh a month, this load cannot be running continuously, and something in your reading is wrong. Do not tell the customer what they will save; tell them what you measured and let the next bill show it. See related: Savings Claims Without Overpromising: The Honest Language.

Step 6: Restore everything and prove it is restored

Turn back on anything you switched off at the device, in reverse order of your list. Set the thermostat back to its original mode and setpoint and confirm the system starts on its own delay rather than forcing it. Read the panel one more time with your eyes: every handle in the same position, none tripped to the middle. Reset any GFCI the test tripped and any timer the customer flagged in Step 2. Then take one last meter reading with the house running normally and compare it to Step 1: it should be in the same range, less the load you found if the customer chose to leave it off.

Why this step exists: the test is only finished when the house is back to where you found it, minus the one thing you agreed to change. Anything else you leave behind becomes the next call.

What changes the method

• Solar on the house. A net-metered meter can run backward or show received energy in daylight, which hides the baseline. Run the test at night or with the solar disconnect off per the system owner's instructions. See related: Net Metering and Net Billing: What a Solar House Bill Is Saying.
• A load too small to see on the disk. Below a hundred watts or so, one revolution takes over a minute and cycling loads swamp the difference. Switch to a plug-in watt meter at the receptacle, or an energy monitor on the circuit. See related: Using a Home Energy Monitor to Find a Problem Load.
• The load is intermittent, not constant. A well pump, a heat tape on a thermostat, or a pool pump on a timer may be off during your twenty minutes. If the bill pattern says the problem lives at 3 AM, get the interval data instead of standing at the meter. See related: How to Get a Customer's Interval Usage Data Without Their Password.

References

• See related: Using a Home Energy Monitor to Find a Problem Load
• See related: Standby and Phantom Loads: What Is Worth Chasing
• See related: How to Diagnose a High-Bill Call, in Order
• See related: kW Versus kWh: The Difference That Confuses Every Bill Call
• Meter faceplate data and the serving utility's meter-access rules