How to read a Visiontek three-phase net meter: import, export and net in three screens

After solar, you will want to know three things between bills: how much you have taken from KSEB, how much you have sent back, and where the two stand against each other. All three are on the net meter, but the meter shows a dozen other screens on the way, and different models order them differently. This walkthrough is for the Visiontek three-phase net meter, the 37TM model, which KSEB fits on many three-phase solar connections in Kerala. Check the model on the front of yours before following it screen by screen; a different model will have the same values in a different order.

The buttons and the reset point

The meter has two push buttons, up and down, and everything is reached by stepping through pages. There is a reset point, a home screen; pressing forward from it walks the pages in a fixed sequence. The first few are identification and live values: the meter's serial number, today's date and time, then the voltage on each of the three phases R, Y and B, then the current on each phase, then the power factor. On the site in the video the power factor read 0.99, which is what a healthy home with a modern inverter should show.

Next comes live power, the instantaneous flow through the meter. The interesting part is the direction. With a 3 kW system running at midday and the house lightly loaded, this screen showed about 725 watts flowing out to KSEB. If the house were drawing more than the roof was making, the same screen would show power flowing in. It is a snapshot, not a total, but it is the quickest way to see whether you are exporting right now.

Screen one that matters: cumulative import

Keep stepping forward and you reach a screen marked IMP, with a cumulative figure: the total units imported from KSEB since the meter was installed. On the video site it read 95 units. Two rules here. Take only the kWh value. The meter also shows kVAh figures, apparent energy, which are used in some commercial tariffs but not for your domestic settlement; ignore them. And the figure is cumulative, so your monthly import is this month's reading minus last month's, exactly as the bill calculates it.

After the import total, the meter shows the same import split by time zone, T1, T2 and T3. These are the periods KSEB uses for time-of-day tariffs. You do not need them for a solar settlement on a domestic connection, so step past them.

Screen two: cumulative export

The screen marked EXP is the mirror image: total units sent to KSEB. This site showed 104 units exported, against roughly 140 units the plant had generated in the same period. The gap is the daytime consumption of the house, the units used live before anything was left to export.

Export is also split by time zone, and here the pattern is a useful sanity check: all of it sits in T1, the 6 am to 6 pm zone, because that is the only time a solar plant produces. T2 and T3 should read zero. If they do not, something odd is happening with the wiring or the meter, and it is worth a call to your installer.

Screen three: net, and what the sign means

The meter then shows net active energy, which is simply import minus export. On this site: 95 minus 104, a net of minus 8 units. The sign is the whole story. A negative net means you have sent KSEB more than you have taken; those 8 units go into your banking on the next bill and are carried forward. A positive net means you have taken more than you sent, and the difference is what you will be billed for, at the applicable tariff, before fixed charges and meter rent.

So the shape of a good month, on the meter, is: export growing faster than import, and a net that stays negative or hovers near zero. Through the monsoon it will drift positive as generation falls and you draw on the bank you built in the bright months. That is the system working as designed, not a fault.

Three values, once a month

IMP, EXP, and net. Note all three on the same day each month, ideally the day before the KSEB reader is due, and keep them with your bills. Then when the bill arrives, the import and export figures on it should match what you wrote down. That is the check that catches a mis-entered reading while it is still easy to correct. Your inverter app tells you what the roof made; the net meter tells you what KSEB saw. You need both, and now you can read both.