How to read your solar meter and electricity bill

The three places to read

1. The inverter. Its screen, and its app if it has one, shows the units your panels made today and the total since it was installed.
2. The net meter. PSPCL fits a bi-directional meter when a system is connected under net metering. It keeps two running totals: units imported from the grid and units exported to it.
3. The bill. PSPCL reads the net meter and bills you on the units you drew, after taking account of what you exported.

Some systems also have a separate one-way generation meter, which counts only what the panels make. If yours has one, it should roughly agree with the inverter.

Reading the net meter

A net meter’s display steps through several readings in turn, either by itself or when you press the button on its front. Among them are the import total and the export total, both in kWh (one kWh is one unit). Meters from different makers label them differently, so check the meter’s leaflet, or ask us to point them out on your meter the first time.

Both totals only ever go up. What matters is how much each has grown since your last reading.

The sum that tells you what you used

No single meter shows your home’s real consumption, because some of what the panels make is used directly and never passes through the net meter. Work it out like this:

Of what the panels made, the part you did not export went straight into your home. Those are the units worth the most to you, because each one replaced a unit you would otherwise have bought.

Keeping a simple record

On the same date each month, write down four numbers: the inverter’s total, the import total, the export total, and the date. Subtract last month’s figures and you have the month’s generation, import and export. A notebook or a phone note is enough.

After a few months you will see the pattern. Generation is higher from spring to early summer and lower in foggy winter weeks. Averaged over a year, we plan on roughly 100 units a month for each kW of panels in Punjab; how many units 1 kW makes explains the figure and how it changes by season.

When to look closer

• Generation falls well below the same month last year, in similar weather. The panels may need cleaning; see solar panel maintenance.
• The inverter shows zero on a sunny day, or an error on its screen. Photograph the screen and send it to us.
• The export total never rises, even on bright afternoons when the house is quiet. Either you use everything you make, which is fine, or something needs checking.

Reading the bill

A PSPCL bill after net metering shows the previous and current readings for import and export, and the units it charges you for. Fixed charges and any duties still appear, because solar changes the units you are billed for and not the connection itself.

How exported units are credited is set by PSERC’s net metering rules. How net metering works in Punjab explains it, and why a unit you export is generally worth less than a unit you use yourself.

If a bill does not match your own readings, compare the dates first: PSPCL’s reading date is rarely the day you read the meter. If they still disagree, send us both and we will go through them with you.