Electricity Bill Part 2: Impact of Solar Panels

In Part 1, we explored how to read an electricity bill, and now in Part 2 we will explore the impact our solar panels had on our bill. The Inglewood Community League had its solar panel system installed in October 2019. Now that spring is here, the sun is out longer, the snow has melted off our panels, and we are generating a great deal of electricity! In April, we saw an immediate impact on our electricity bill and wanted to share it with the community. Solar panels will impact your bill in two ways.

The first way solar impacts your bill is any electricity generated in excess to what you are consuming within the building is sold back to the grid. This shows up as a credit directly on your electricity bill as “MircoGen”. In March, we exported 1280 kWh, nearly double our import of 680 kWh.

Credit on our electricity bill for exported solar power

It is important to note that when exporting electricity (i.e. selling back to the grid), we get credited at electricity rate (7.104 ¢/kWh). We are not credited the variable delivery charges on exported electricity, but are not charged for them either. The delivery and transmission infrastructure (i.e. power lines) are still utilized when exporting and therefore we not doing anything to warrant a credit on delivery.

As an aside, the average usage in March for the last three years was about 1400 kWh. Our consumption this year was less than half the average. This change was primarily from the hall being shut down due to COVID.

The second way solar panels impact your electricity bill is not actually observable on the bill itself. This is the electricity which is generated and then self-consumed; i.e. consumed in the building rather than being exported to the grid. If there were no solar panels, we would otherwise be importing/buying this power from the grid. Our solar inverters have an added electricity meter which allow us to better record how much we have self consumed.

March 2020 Solar Production

For the date range of our bill, we used our SolarEdge data portal found to have self-consumed 33 kWh during Feb 27-Feb 29 and 240 kWh Mar 1-Mar 25. Knowing this, we can now re-calculate the bill by adding in the self-consumed power and removing the Microgen export. The “with solar” column is our actual bill, and the “without solar” gives us an accurate comparison of what our bill would have been without solar. The values that changed are highlighted in yellow, which is everything except the fixed costs.

Recalculation of Electricity bill without solar

The total difference between the two scenarios is $137.67. Not only are we getting credited $91 on what we export, but we have saved an extra $40 by self-consuming an extra 263 kWh! For the electricity you export, you get credited only the electricity rate, approximately 7 ¢/kWh. For electricity you self-consume, you are avoiding importing/buying which means you are effectively saving ~16 ¢/kWh, about double!

DescriptionAmount
MicroGen Export $   90.93
Self-Consumption $   40.18
GST $    6.56
Total $  137.67
Breakdown of money saved with solar – March 2020
Breakdown of money saved with solar – March 2020

Key Takeaway 1: Solar panels impact your electricity bill in two ways. a) The amount you export which is visible right on your bill and b) The amount you self consume, which is hidden and impacts your bill without you ever seeing it.

Key Takeaway 2: You get the most bang for your buck by self-consuming electricity. Each kWh you self consume is worth 2-3 times more than a kWh exported! With solar, if you can shift more of your electricity usage to daytime hours when the sun is shining, such as washer and dryer, you will save substantially more money!

I hope you enjoyed these articles. We are half way through our first year with solar, and I have several more topics ready to dig deeper into. Stay tuned!

Electricity Bill Part 1: Understanding Your Bill

Your electricity bill gives a great deal of information, but only if you know what to look for. The most common misconception is that the delivery charges are all fixed fees, and reducing your electricity usage will have little to no impact on your bill. In fact, most of your bill is variable including most of the delivery charges. This myth is propagated since the long list of delivery charges and riders do not have their rates stated anywhere in the bill! In part 1, we will explore the components of your electricity bill, and how to read it. Our electricity retailer is EPCOR, but there are many other retailers that serve Edmonton. While other retailers may present the bill slightly differently, the same overall concepts apply.

The Inglewood Community League has three different electricity services, and three separate meters. Service 1 is for our field hall, which is slated for demolition and currently powered off at the main breaker. Service 2 is for our parking lot lights, which typically add about 5% to our monthly usage. Service 3 is for the main hall, including the solar panel installation. For simplicity, we will only discuss Service 3 in this article.

Inglewood March 2020 Electricity Bill

The bill is broken down into two parts:

  1. Electric Energy Charges: This pays for the actual electricity, an administration fee, and a credit for the electricity we sold back to the grid from our solar panels (MicroGen).
  2. Delivery Charges: The delivery charges pay for the infrastructure to deliver electricity to your home. Most of these fees are variable, however this is not made clear on the bill.

While electricity rates are clearly shown on the bill, delivery rates are not. The rates change month to month or quarter to quarter and can be found on the EPCOR website, although unfortunately not in an easily accessible way.

There are three different types of charges, each highlighted a different colour on the bill:

  • Fixed: The “Administration Charge” from EPCOR is $5.59 per month.
  • Mixed: The “Distribution Charge” has is made up of two components: a daily fixed fee (currently 37.844 ¢/day), plus a variable fee (currently 2.669 ¢/kWh). There were 28 days in this billing period, which means $10.60 (about 1/3rd) is the daily fixed fee.
  • Variable: All other fees are variable and are charged in ¢/kWh. These scale directly with how much electricity you consume.

VARIABLE COSTS: THE TRUE COST OF ELECTRICITY

All the variable costs on the bill are what we consumers actually pay to use electricity in our homes/buildings, and can be summed up into a single monthly rate with units of ¢/kWh. The total variable cost we end up paying each month is often 2-3 times the amount as the raw electricity rate we see written on our bill, that most of us tend to focus on.

Total electricity cost in ¢/kWh

SIMPLIFIED ELECTRICITY BILL

The average consumer is not interested in the breakdown of electricity vs. delivery costs. From a billing perspective, it makes more sense to split between variable and fixed. A simplified bill is presented below using the total variable rate from above. I find this a much more transparent way to to breakdown how your money is actually being spent. Note that there is 1 cent difference between this and the EPCOR bill due to some early rounding from EPCOR.

Simplified Electricity Bill

A simple pie chart shows the breakdown of fixed vs. variable costs on this bill. For simplicity, and to make it more in line with an average home users bill, it excludes our solar panel export and GST.

Comparison of Fixed vs. Variable costs

Key takeaway: Delivery charges are not fixed! They are mostly variable and depend on your electricity consumption. They can effectively double or triple your electricity rate!

Next up in Part 2, we will explore how our Solar panels impact our bill.

The Impact of Snow

We’ve had a fair bit of snow this winter, which has been impacting the production of electricity from our solar installation. This was entirely expected, and according to NAIT, we should only see about 5% drop in production on average over the course of the winter due to snow. In the winter, the sun is so low in the sky and for such short days that the snow cover has a pretty minimal effect overall. Once spring hits, the winter performance won’t really matter at all!

After a pretty dismal December through to most of February, this warm spell has finally melted the snow cover. This photo was taken on the 22nd, two days before it fully melted.

February 22nd at 4:45 PM. Photo has been perspective corrected.
February 22nd at 4:45 PM. Power output per module.

There are a few interesting observations here. We can easily see that even minor coverage of a module significantly impacts the production. This is most apparent in the top row on modules 1.1.7 and 1.1.8, which have snow covering just a small portion of the bottom, but the output has dropped by half or more.

We can see that the snow guards are working effectively. In an ideal installation, there would be no snow guards and the snow would easily slide off. Due to our proximity to the playground, a robust snow retention system was installed. While this helps keep our children safe, it causes some extra snow accumulation. A worthy compromise by any standard!

The pattern of how the melting occurred is also interesting. You can see here, and I’ve observed on other days, that far left and right melt first, while the center stays covered. There may be poorer or degraded roofing insulation around the vents and chimney, which leaks heat from the building, warming the modules from below and melting the snow. The central area is clear of vents and the building insulation is probably better, resulting in more snow accumulation.

Each colour coded section is a string of 13 or 14 modules. Each inverter has two strings.

Another phenomenon we can see is that some modules, even though they are clear of snow, have very little output. You can see this most clearly in the bottom left (2.2.1 and 2.2.2) but also in the middle row (2.1.2 and 2.1.11-13). To explain this, we need to explain how the system is laid out. We have two inverters, each with two strings, for a total of four strings. For our purposes, each of these 4 strings effectively operate independently. Our inverters expect an input voltage of about 400V, and the current is the same through all modules in a string. With optimizer outputting with the same current, they need to adjust their output voltage to optimize the voltage.

Solar module optimizer voltage at February 22nd at 4:45 PM. Snow cover and shadowing overlain.

On the far right, string 1.2 has all twelve modules free of snow and shadow. Each is outputting roughly the same at 33 Vdc, and the entire string is at 392V. The top string (1.1) has some shading and snow cover, so the lesser producing modules operate at a lower voltage, while the higher producing modules output at a higher voltage.

On string 2.2 (the bottom row), there are three modules outputting 60V, the max for the optimizers. There is still enough voltage to hit the minimum for the inverter, the current is very low (I calculate 0.1 Amps). This means that the production of the three clear modules is capped at 60V * 0.1A = 6W, which is close to what we see in the first image showing ~8W. If microinverters were used here instead of SolarEdge string optimizers, we would be able to get the full 80W out of each of these three modules, a difference of 68W.

Likewise on string 2.1 (the middle row), there is a bit less snow cover and the current higher at about 0.8 Amps. For the four optimizers at 59V, this means they are capped out at 59V * 0.8A = 47W, roughly what we see for the four top producing modules. For each of these, we are losing out on a potential 30W per module.

Overall, this particular issue doesn’t have much of an impact. At this snapshot in time we are looking at a loss of about 200W for a few hours a day for a few weeks a year. A rough calculation puts this at around 16 kWh, or about $1.50 per year in electricity. Clearly not a major impact, but an interesting exercise nonetheless!

Solar Education for Inglewood Grade 5 Class

The Inglewood Community League and our Solar installer Generate Energy recently hosted the Inglewood Elementary School grade 5 class at the hall for some class about solar energy! Special thanks to Jeremy and Beth from Generate Energy for educating the class about solar energy generation. This included hands on with all the different system components (modules, optimizers, and inverters) and how systems are designed. They even brought in some fun solar toys!

The timing of this was great, and coincided with our system coming online and the grade 5’s electricity and magnetism lesson.

This was the first of many of our planned community engagement programs! Stay tuned for more! 

First Day of Production!

The system is now operational, and our first full day of production was October 31st, 2019! There were brief periods of full sun at around 11:30 AM and 1:30 PM, but was otherwise unfortunately a relatively cloudy day. We generated 15.7 kWh for this first day, which is about half of the expected average for this time of year according to simulations by pvwatts. We are heading into the least productive part of the year, so won’t be seeing a top production for a few months. There are plenty of milestones we can hit this winter!