After a rough start, I now love our rooftop PV system

It’s been over 3 months since our rooftop system has been hooked up to net metering. I remember the day, October 31st, 2017 when our utility (PECO), replaced our old meter with one that could read the flow of electrons in both directions.

The installers got the panels onto our roof in early August. But to get the generation from our panels interconnected with the grid took some time. This was critical, because we wanted net metering – credit for excess generation that was fed back to the grid.

Why the 3 month delay? The power line to and from our house could have high voltage, said our utility. Meaning sending homegrown electrons out to the grid could be unsafe. The recommendation? Join a pilot program to use an inverter that would limit the voltage we’d push onto the line.
We jumped on this suggestion. But, the initial settings caused the inverter to turn off when voltage hit 253 Volts for one second, taking 5 minutes to come back on. This happened so often (663 times in a 2-week period, for a total of 55 hours of lost generation) that I began dreading sunny days and system shutdown. In fact, our system appeared to work better on cloudy days. 
To share my frustration visually, take a look at the 2 charts below showing solar production throughout the day. The one on the left is our system; the one on the right is a neighbor’s, on the same day. Our system kept shutting down, right at mid-day, wiping out the beautiful green hump of solar generation that the neighbors saw.

It took a few phone calls with both PECO and our installer, and a re-reading of the PUC regulations, to discover that a setting change (power down the system only after a full minute of high voltage, instead of one second) could resolve this. That made all the difference. Now I’m in love with sunny days and my chart looks more like my neighbor’s.

Our system has been running nicely since mid-November, about 3 winter months. From that date through the end of February,  we generated 1,604 kWh of solar electricity. Our household used 512 kWh of that before it went to the grid, and we imported 1,068 kWh from PECO, mostly at night, for a net export to PECO of 24 kWh. Agreed, this is a tiny amount, but this was over the winter! Given that generation is expected to be much higher in other seasons, this should allow us to gradually replace gas appliances to electric, and eventually charge an electric car.

How big is our system? A total of 29 panels, 12 on the roof facing southeast, and 17 on the rear southwest roof, at a few different angles on an 1880’s Victorian with steep roofs. We selected 335 Watt panels, for a total system size of 9,715 Watts (9.7 kW). Curious what this looks like? Take a look at the time lapse photography of the installation.


Whatever became of our 1st buying group from February?

Having recruited a dozen households for rooftop solar in February, the first installation began in early March. Seven months later, we have ten completed installations enjoying electricity from the sun.

The last two installs were in late August and early September.

Our eleventh household had some challenges with PECO’s transformer supplying their house. This has caused a major delay, but they are now waiting on PECO to do some work and should be able to move forward soon.

The first install, completed in late April, has produced seven megawatt hours of electricity so far! The homegrown electricity not only runs their household, it also charges the family car, a Nissan Leaf, while pushing the surplus generation back onto the electrical grid. Their monthly electric bill has dropped to $8.45, the minimum to maintain an account with PECO.

If you like charts, you’ll love the one below about this same household. Yellow is daytime electric use; blue is nighttime electric use. Columns are the 23 months before their installation went live, and the few months after. You’ll notice the expected seasonal variation, but see what happens after April. At night, they still get electricity from the grid. But their monthly average usage is negative, and has been for the six months so far. They are thrilled with their decision.

Pushing electricity onto the grid has many steps: Make the decision, Sign the contract, Obtain interconnection go-ahead from PECO, Obtain permit from the City, Order the solar panels & components, Install the system,
Coordinate City inspection, Coordinate meter replacement by PECO, Register for SRECS (Solar Renewable Energy Certificates). Remember if you are considering solar, you only need to do the first two steps. The installer takes care of the rest!

Below is the chart showing all the steps, completed and not, for each household in our first round. The steps are down the side, and the number of households is along the bottom. Soon, this chart will be all green!


Rooftop solar and your PECO bill

This post will explore the PECO power bill, before and after going solar. Be sure to check out the “Interesting Issue” near the end of this post.

Looking at a sample of page 2 of a PECO electric bill before going solar, you’ll see 

  • one meter reading showing monthly usage (451 kWh in our sample)
  • one fixed Customer charge of $8.44
  • three charges based on usage for Generation, Transmission & Distribution.

If you’ve gone to PAPowerSwitch and selected another electricity supplier, then you would see Generation & Transmission combined onto one line, with the rate set by that supplier.  

On your first month with solar, it will be a bit complicated for two reasons.

  1. PECO charges the installer for the new meter (part of your payment to the installer), and then PECO gives you a credit on your bill. The amount is between $300 and $400.
  2. You’ll therefore be billed part of the month with the old meter, and the remainder with the new meters.

You’ll see a bill like the one below with 3 meter readings:

  1. Old meter reading, partial month’s usage before switch to solar (sample: 81 kWh)
  2. New “in” meter (also called general service) for electricity you used from PECO (sample :232 kWh)
  3. New “out” meter, for electricity your rooftop system sent to PECO (sample 340 kWh)

plus a Customer charge of $8.43 (or 8.44, not sure why it varies a little).

What this means:
The energy from solar that was sent back to PECO was 27 kWh more than the amount received from PECO (340 – 232 – 81). This surplus 27 kWh will be banked towards next month’s use. You are billed just the Customer charge of $8.43 for the month.


To make it more complicated, for this particular bill, the 27 kWh surplus resulted in a  “Renewable Energy Credit” of $2.15 because the bill happened to be in May which is the month when PECO zero’s out the banked distribution of kWhs. They call this “settlement.”

This plus the credit mentioned earlier, for the meter, results in a total credit of $327.06.  Given that the customer charge was $8.43 the bill ends up with a credit of $318.63 that will be carried over to the next month. The image below is Page 1 of the May bill.
Note the “Message Center” which describes the “banked distribution” and the “settlement.”

The following months, when your grid-connected system is in full swing, you’ll see a bill like the one below:

  • 2 meter readings:
    “In” meter, for electricity you used from PECO,  (sample 287 kWh)
    “Out” meter, for electricity your rooftop system sent to PECO, (sample 525 kWh)
  • Customer charge $8.43

In the example, 238 kWh more electricity was sent to the grid than you pulled down  (525-287) . The surplus will go into your “banked distribution” and will be added to next month’s “out” meter reading to determine next month’s bill. If the total of these two is more than the “in” meter, then no charge, if it is ever less than the “in” meter, then you will see the three charges for generation, transmission and distribution for the extra kWh’s used.  This rollover and comparison will occur each month until the next May. In May, PECO will zero out the surplus “banked distribution” with a check or a credit on the bill.

INTERESTING ISSUE – There is one piece of usage information that is not visible on the PECO bill: How much electricity was actually consumed by the loads in the house. Since solar energy is used by the house loads first, PECO does not see this energy so can not meter this energy.

On the 13-Month Usage chart shown above, compare the usage for the prior year’s month of June, before the solar installation, to June of the current year which was after the solar installation. The current year is significantly lower than the prior year. This is because the big usage in June is the air conditioner, and the air conditioner tends to be on during the day when the sun is out and power is being generated by the panels. This is a clear picture of the value of solar because the electricity for the air conditioning load never had to enter the electrical grid. The electricity was consumed right where it was generated.   

The load information is not lost to the homeowner as it is being tracked by the monitoring system from the solar company which is used to track the output of the solar arrays.

This data in combination with the information available on the PECO bill will allow a full picture of the energy flow.


May 20th update on our 1st group of solar installs

Two more homes have their panels connected to the grid and generating electricity for a total of three!

See the updated chart below listing the steps required to fully implement rooftop solar, along with the status for each of our 12 initial households.

Green = number of households that have completed each step
Red = number of households not yet completed.

Dara Bortman from Exact Solar is managing each of these steps to ensure a smooth process.


Where are we with our 1st group of solar installs?

Kicked off last October, by the end of February, we had 12 area households step up for rooftop solar installations. Two and a half months later, 3 homes have panels on their roofs. One of these is connected to the grid and generating electricity.

We’ve learned there are quite a few steps to the installation process. See the chart below listing the steps required to fully implement rooftop solar, along with the status for each of our 12 initial households.

Green = number of households that have completed each step
Red = number of households not yet completed.

Dara Bortman from Exact Solar is managing each of these steps to ensure a smooth process.


see your PECO bill online

Ever wondered how much electricity you use in a year? Or how all your energy saving devices actually reflect on your electric bill? You can see this and more at, even compare your usage with your neighbors. Here’s how:

  • You’ll need to setup an online account on your first visit to
    1. Go to
    2. Under the log-in boxes, click Register
    3. Enter your account number, your primary phone number associated to your account and the last 4 digits of the primary account holder’s social security number or business tax id.
    4. You will then need to create a password.
  • Once logged in, you can see your current bill, check out the history, enroll in auto pay and other payment options.
  • To get a copy of your bill, go to My Bill Details where you’ll see a button that says Download Bill PDF.  Scroll down to bottom of page 2, where you’ll see Your Usage Profile. The Total Annual kWh Usage shown here is used to determine the system size when you inquire about rooftop solar. If possible, print this page 2 when you come to one of our member meetings.  On average, each Pennsylvanian home uses about 10,000 kWh per year. With energy efficient devices, it’s possible to use only about half that.

  • You can also see how your energy use compares to neighbors with similar sized homes. You can find this under My Account, then choose My Bill & Usage,  and then click on the neighborhood comparison tab under View Bill Details.
  • Want to see your usage over time? To see charts of this overlaid with the average monthly temperature, go to My Account, choose My Bill & Usage,  and then, on the Electric Bill Usage tab, scroll down and click on View detailed usage“.

The site has a lot of other information as well where you’ll discover you can check for outages, even report outages.

Curious about how to use less electricity? You should be when considering investing in solar, since you’ll need fewer panels to generate enough electricity for your needs. See tips for saving energy under Ways to Save.

If you need help deciphering all this data, come to our next member meeting where neighbors await to translate this for your life.