How does a net meter work with solar?

It records energy flowing into the building and energy flowing out on separate registers. At any instant it sees the difference between what the array produces and what the building uses, not the array's total output. The two registers are read separately for billing.

Why does my meter show zero during the day when the panels are producing?

The import register falls to zero when on-site production covers the building's load. Export appears on a different register, which the display may cycle to a few seconds later. A zero import reading at midday is normal and does not mean the array has stopped.

Do I need a second meter for solar?

Only if the programme the system is enrolled in pays for production rather than for export. That is a utility and state rule, not a technical requirement. The utility specifies the meter and the wiring point, and the work is licensed.

Can I read production from the utility meter?

No. The meter is at the service point and measures net flow. Production is reported by the inverter or by a separate production meter. Comparing the two over a day shows how much of the array's output was used on site.

Who changes the meter when solar is installed?

The utility or its contractor. The meter and the service conductors are utility property, and the work is not done by the homeowner or a general electrician. The change is a step in the interconnection process and can affect the timeline.

How a Net Meter Reads Solar Import and Export

A grid-tied photovoltaic system shares one piece of equipment with the utility that the owner rarely thinks about until a bill arrives: the meter. Once a PV system is connected, the meter no longer measures consumption alone. It measures flow in two directions, and the way it records that flow determines what appears on the bill. The rules governing that recording are set by the state and by the individual utility, and they change; nothing in this page should be read as a statement of what a particular utility does. It describes what the hardware is doing and what the owner has to look up.

What the meter measures, and what it cannot

A conventional electricity meter accumulates energy passing from the grid into the building. A bidirectional meter, often called a net meter, accumulates the same quantity but keeps a separate register for energy passing the other way, from the building out to the grid. The two registers are sometimes labelled import and export, sometimes delivered and received, sometimes with numeric codes on a cycling display.

The important limitation is that the meter sits at the service point, not at the array. It sees the net of production and consumption at any instant. If the array is producing 4 kW and the building is drawing 3 kW, the meter sees 1 kW of export. It does not see 4 kW of production. Production is measured by a separate device, or not at all.

That distinction matters because some programmes pay for production rather than for export, and those programmes require a production meter, sometimes called a solar meter, wired between the inverter and the service panel. A production meter is a second meter, owned or specified by the utility, that counts every kilowatt-hour the array makes regardless of where it goes. Whether one is required is a programme rule, not a property of the technology.

Reading the display

Most modern meters cycle through several screens. The exact codes are set by the manufacturer and by the utility’s configuration, so the same code can mean different things on different systems. The general pattern is that one screen shows total energy imported, another shows total energy exported, and others show instantaneous power, time and date, and diagnostic registers.

A few conventions are common enough to be worth knowing before looking anything up:

A register labelled with a direction arrow pointing toward the building is import.
A register labelled with an arrow pointing away is export.
Instantaneous power may be shown as a signed number, with negative meaning export.
Some displays alternate between registers every few seconds; others require a button press.

None of this substitutes for the utility’s own documentation. The register layout is configured when the meter is commissioned, and a meter installed for a solar account may have registers disabled or renamed relative to the same model on a non-solar account.

Why the meter is changed

When a PV system is interconnected, the utility frequently replaces the existing meter with one capable of recording export, or reconfigures the existing meter if it already supports bidirectional registration. The work is done by the utility or its contractor. The meter is utility property, and the service conductors on either side of it are not a place for the owner or a general electrician to work. Anything involving the meter enclosure, the meter socket, or the service conductors is licensed electrical work and, in most jurisdictions, utility work specifically.

The meter change is also a point where the timeline can slip. The interconnection application, the utility’s review, the inspection, and the meter swap are separate steps, and the array may be energised before the new meter is in place. During that interval the old meter may run backwards, may record export as import, or may simply not register it. That is a billing question, not a safety question, and it is resolved with the utility.

Net metering, export compensation, and the limits of a general answer

Net metering is the arrangement in which import and export are netted against each other over a billing period. It is one of several possible arrangements. Others include compensation for export at a rate different from the retail rate, compensation only for a portion of export, or no compensation for export at all. Which applies depends on the state, the utility, the programme the system was enrolled under, and the date of enrolment.

These rules change. A system interconnected under one set of rules may be grandfathered under those rules for a period, or may not. The reader has to check four things with the utility and the state public utility commission:

Whether the account is on net metering, a successor tariff, or a buy-all/sell-all arrangement.
Whether compensation for export is at the retail rate, a avoided-cost rate, or something else.
Whether unused credit carries forward, and for how long.
Whether a production meter is required, and who pays for it.

No page can answer those for a given address. The utility’s interconnection agreement and the state commission’s current order are the sources.

Where the diagnosis goes wrong

Observation	Likely cause	When this cause does NOT apply
Meter shows export but bill shows a charge for it	Export compensated at a rate below retail, or not at all	Account is on true net metering with monthly netting
Meter shows no export at midday	Export register disabled, or production never exceeds site load	A production meter is installed and reading normally
Meter runs backwards	Older electromechanical meter without a detent	Meter has been replaced with a bidirectional unit
Bill shows consumption higher than expected	Interval includes fixed charges and fees, not just energy	Bill is itemised and energy line alone is high
Production meter reads lower than inverter	Clipping, soiling, or inverter derating	Inverter and meter are within a few percent over a full day

The most common misreading is treating the export register as a production figure. It is a natural mistake because the number rises on sunny days and falls on cloudy ones, which is exactly what production does. But the export register is production minus consumption at each instant, summed. A house that uses most of its solar output on site will show a small export figure even when the array is performing to specification. The error is not carelessness; the meter is doing what it was designed to do, and the display does not announce the difference.

The second common misreading is expecting the meter to show a negative consumption figure during export. On a bidirectional meter, import and export are separate registers, not a single signed total. A display showing zero import at midday is consistent with substantial export on the other register.

Checking a reading without touching the DC side

The array produces dangerous DC voltage whenever there is light on it, and that voltage cannot be switched off at the panel. Nothing in this section involves opening a combiner, probing a string, or disconnecting an energised connector. The checks below use the meter display, the inverter’s own interface, and the utility bill.

# On the inverter's local interface or monitoring portal, note
# today's production in kWh. This is the array's output, not the meter's.

The inverter reports production directly. Compare it with the meter’s export register over the same interval; export should be less than or equal to production, and the gap is self-consumption.

# On the meter display, cycle to the import register and record the value.
# Cycle to the export register and record the value.

If the export register does not change across a sunny midday period while the inverter reports production, the register may be disabled or the meter may not be configured for bidirectional operation. That is a call to the utility, not an invitation to open the enclosure.

# Compare the utility bill's energy line with the meter's import register
# for the same billing period.

A mismatch between the bill’s energy charge and the import register usually indicates fixed charges, taxes, or a demand component on the bill rather than a meter fault.

# If a production meter is installed, read its total and compare
# with the inverter's lifetime production figure.

A persistent gap of more than a few percent over a full month points to a metering or configuration issue; a gap that appears only in summer points to clipping or high-temperature derating.

Any work inside the meter enclosure, on the service conductors, or on the DC array is licensed work. Roof work and mains connection are licensed trades. The meter itself belongs to the utility.

What to ask the utility

When the numbers do not reconcile, the productive questions are specific: which registers are active on this meter, what rate applies to export, whether credit carries forward, and whether a production meter is required under the programme the system was enrolled in. Those answers are set by the state and the utility, and they are the only answers that apply to a given service.

Bidirectional and Net Meters on a Solar Service