Import units, export units and what net metering does to your bill
After solar, your electricity bill grows two numbers instead of one. Understanding what they mean, and why one of them is worth more than the other, is what turns a solar quotation into a decision you can actually check.
Two numbers, two directions
Before solar, your meter counted one thing: electricity entering your property. After solar, electricity can flow both ways, so the meter is replaced with a bidirectional one that keeps two separate totals.
Import
Units you drew from the grid
Everything you consumed that your array was not producing at that moment: the whole of the night, cloudy periods, and any time your load exceeded generation. These are units you buy, at your retail tariff.Export
Units you sent to the grid
Generation nobody in the building was using at that instant, which flowed outward instead. These are units you are credited for, at the rate the net-metering regulations set, not at your retail tariff.
Notice what is absent from that pair: the units you generated and used. They never touch the meter, because they never left the building. They are the largest part of most systems’ value and they are invisible on the bill, which is why people who judge their system by its export figure alone consistently underestimate it.
How the netting works
01
Generation meets load first
Whatever is switched on consumes solar output directly. Nothing is recorded, nothing is billed, and nothing is credited. This is the cheapest electricity in the arrangement.02
Surplus flows out and is counted
What is left over passes through the net meter, incrementing the export total. This happens continuously through the day as generation and load rise and fall against each other.03
Shortfall flows in and is counted
At night, and whenever load exceeds generation, the grid supplies you and the import total increments. The same meter, the opposite direction.04
The DISCOM nets them at billing
At the end of the billing period your export credit is set against your import charge according to the net-metering rules in force for your connection. What remains is what you pay.
That is the entire mechanism. The complexity people expect is not in the netting. It is in the rates applied to each side, which are set by the state electricity regulatory commission — TGERC in Telangana, APERC in Andhra Pradesh — and revised periodically.
We publish no tariff figure on this page deliberately — rates change by state commission order, and a number written into a paragraph like this one has no way to show you how current it is. Our calculators carry the rate with the date it was verified attached instead.
Why self-consumption beats export
This is the one insight that changes how people use a solar system, and almost nobody is told it at the point of sale.
A unit you consume yourself is a unit you did not have to buy. Because solar displaces your most expensive units first (the ones in your highest tariff slab), that avoided unit is worth your marginal retail rate, which is the highest rate you pay. A unit you export earns the net-metering credit rate instead, which is generally lower.
So the same kilowatt-hour is worth noticeably more used than sold, and the difference is entirely within your control. Running the washing machine, the water heater, the pump or the pool filter during daylight rather than in the evening moves units from the export column into the invisible self-consumption column, and increases what the system saves you without changing a single piece of hardware.
It also has a consequence for sizing. A system substantially larger than your daytime consumption pushes an increasing share of its output into the lower-value export column, so each additional kilowatt returns less than the one before. Right-sizing to your consumption pattern generally beats maximising capacity, which is what the ROI calculator is modelling when it asks how much of your usage falls in daylight hours.
What stays on your bill regardless
Solar reduces the energy component of a bill. Several other components are levied on the connection rather than on consumption and continue whatever your array does:
- Fixed or service charges tied to your sanctioned load, not to units consumed.
- Demand charges on commercial and industrial connections, based on peak demand drawn, which solar reduces only if it happens to be generating at your peak.
- Duties, cess and statutory levies, applied per the tariff order.
This is why a bill rarely reaches zero and why anyone promising that it will is describing one line of it. Once you can read the two meter totals and separate the energy charge from the rest, you can check any savings claim anyone makes to you, including ours. Next, see how a solar system works for the equipment behind those numbers, or Solar On-grid for the configuration this all assumes.
If your generation looks low for your system’s size, see our solar maintenance guide or annual maintenance options.
Common questions
What is an import unit and what is an export unit?
An import unit is a kilowatt-hour you drew from the grid: at night, or at any moment your consumption exceeded what the array was producing. An export unit is a kilowatt-hour your system produced that nobody in the building was using at that instant, so it flowed out to the grid instead. A net meter counts both, as two separate running totals.
Why is my export number lower than I expected?
Because your building consumes generation first. Export is only the surplus after everything switched on at that moment has taken what it needs. A house with a daytime air conditioner or a business running through the working day can generate a great deal and export very little. That is not a fault. It is, in fact, the more valuable pattern.
Is an exported unit worth the same as one I use myself?
No, and this is the most important thing to understand about solar economics. A unit you consume yourself avoids buying a unit at your retail tariff, including the higher slab rates, since solar displaces your most expensive units first. An exported unit is credited at the rate your DISCOM applies under the net-metering regulations in force, which is generally lower than retail. Self-consumption is therefore worth more per unit than export.
What happens to unused export credit at the end of the year?
That depends on the net-metering regulations your DISCOM operates under, and the treatment of surplus at the end of a settlement period is set by the state commission rather than by your installer. It is a question worth asking your DISCOM directly, or asking us to confirm for your specific connection, before sizing a system substantially larger than your consumption.
Will my bill go to zero?
Usually not entirely, even with a well-sized system. Fixed charges, demand charges and duties are generally levied on your connection rather than on your consumption, so they continue regardless of how much you generate. Solar reduces the energy component of the bill. A quotation promising a zero bill is describing the energy charge and quietly omitting the rest.
Do I need a new meter for solar?
Yes. An ordinary meter counts flow in one direction only. Net metering requires a bidirectional meter, and its installation is a DISCOM process with an application, approval and inspection sequence rather than something an installer simply fits on the day. Until it is in place, exported units are not being credited to you.
What do import, export and generation mean on a solar bill?
Import is the units you drew from the grid. Export is the surplus units your system sent out to it. Generation, where your bill or meter shows it, is the total your panels produced. That total splits into what the building used directly and what was exported, so generation is always at least the export figure, and when both readings cover the same period, the difference between them is what you consumed yourself.
What does it mean if my import units are more than my export units?
This is normal for many homes with solar panels. You still draw electricity from the grid at night, in the evening, or whenever your panels are not producing enough. Under net metering, how exported units are credited against imported ones depends on the billing rules that apply to your connection and your DISCOM. Higher import than export does not by itself mean the system has a fault. If your solar generation looks unusually low for your system's size, have the system checked: our solar maintenance guide and annual maintenance options, linked on this page, cover what to look for.
Bring your last bill
A free site survey with a recent bill in hand gives you real import figures, your actual slab, and a system sized to your consumption rather than to your roof.