Solar Power Monitoring with SolarCity

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solarpanels runningAfter many struggles getting my SolarCity system installed and up and running, the system has been up and running since February 23rd, 2015 and I wanted to share a few experiences in monitoring the system and the billing which finally started.

Savings

Once your SolarCity system starts running you immediately benefit from reduced measured kWh usage from your power company. This affects both the supply and delivery portions of your bill and is just like you didn’t use the power.

The reductions can be pretty dramatic, for example last May I used 2,646 kWh and this May I used 238 kWh, or a 91% reduction. The electric company provides a good summary of this too:

SolarCity Before AfterBut my costs didn’t go down by 91%.

Billing

The kWh savings come at a price. Almost everyone who signs up with SolarCity goes with a Power Purchase Agreement (PPA) which means you pay nothing upfront (for the gear, install etc.), but you pay SolarCity for the kWh their system generates. That rate can be variable or fixed. I pay a fixed rate of $0.1420 per kWh generated for 20 years. That may sound high to you but my local electricity rate is $0.2470 so i’m saving 43% per kWh.

I’m saving 43% per kWh with SolarCity.

It takes SolarCity some time to get up and running with their billing system. For me it took them 3 months to send me the first bill so I got a hefty bill (thankfully late winter months) for all 3 months in one shot. After that the bills are coming monthly (note that SolarCity requires EFT/Autopay to be set up).

The bills are not complex and just state the kWh generated and the rate you pay and then the total along with other usual account information:

SolarCity BillIn the following sections i’ll cover how you can see your generation as it happens but there’s a key point to note — the data they give you (the customer) is not the data they use for billing.

Warning: The data they give you (the customer) is not the data they use for billing

In a fit of bad logic/programming/design, while they collect the data from the system that they use for billing over your internet connection and they also collect the data they show you over that same internet connection the two are only loosely related. On my first (large/3 month) bill I found a difference of 10% (additional cost for me) between the billing amount and the amount the system had reported being generated through the charts and tables you’ll see below.

Naturally I called to complain but their billing people are fairly close to useless here and just tell you thats the way it is and then instruct you on reading each of the meters at the beginning and end of each month if you want to confirm things. Not that the meters couldn’t be wrong/rigged.

In the end I track the savings knowing how much I used to use before SolarCity, how much I’m now supposedly using and then what i’m paying and my total cost per kWh.

Since inception i’ve saved $320 (over roughly 3 months) or about 42% off what I would have paid National Grid. And the system cost me nothing to install (I actually got a $1,000 Tesla-owner check from them).

They also have an estimated cost savings on the front page when you log in but its totally incorrect:

SolarCity Estimated SavingsThe mistake they made here is that they’re assuming your electricity rate doesn’t change over time. My electricity rate rose significantly after I signed up for SolarCity and so i’m getting a larger than average savings and one they’re not reporting back to me. No matter, the savings are real anyway even if they’re confused.

If an electricity rate hike is coming sign up for SolarCity before it does.

Monitoring

Monitoring happens online at MySolarCity.com. They unfortunately are more fixated on referrals etc than they are in making good interfaces yet their referral system is also messed up. The section you want is the PowerGuide where you can get a lot of data.

The one I often look at is the daily generation data:

SolarCity - DayThis gives an hour by hour account of your generation as well as the running total for the day and environmentals like how much daylight there is that day and how much cloud cover happened. The different color bars represent each inverter and hovering over them shows the generation per inverter. You can download the data in CSV format and import into Numbers or Excel. You can move forward or back to different days as needed.

If you have multiple inverters the CSV data for the day is a bit of a pain since it also gives the generation data every 15 minutes per inverter.

The month view does the same thing but over a month period:

SolarCity - MonthSimilar data. The CSV has it only broken down by day but still an entry for each inverter for each day.

They also have the summary for the year:

SolarCity - YearFor the CSV is month by month data for each inverter.

As homeowner I don’t care about the individual inverters and including that breakdown in the CSVs is just annoying.

The last piece which is just a bit odd is they have a live view of your generation as its happening updated continually:

SolarCity - LiveThis updates live as you watch it so you can watch the sun rise and set as viewed by your panels 😄 Im not sure what use this view has but its sort of cool, for a brief period.

If you look closely at some of the days you’ll see some odd behaviors:

Odd Solarcity ResultThis is technically impossible but they seem to have no validation around the data. And don’t bother calling them, they’re uninterested in these aberrations.

API – Not

Automated SolarCity TweetSince I have automated tweets for SuperChargers and Tesla Versions I wanted to have automated daily tweets on my solar production. Unfortunately SolarCity doesn’t provide an API for this or even a clean set of web pages that facilitate this. I used a tool called Selenium and some Python code to automate fetching the current day’s data and tweeting it:

It would be really nice if they’d create a simple REST API to fetch this data rather than forcing people to do these odd kind of hacks.

Summary

SolarCity makes a lot of sense for the cost savings it provides with no upfront costs. You have to look at the savings gap between your generation cost versus your electricity cost and decide if the savings is worth the hassle. If you want to see if it can work for you, get started with no commitment by just filling out a contact form, just don’t expect anything to happen quickly.

On the billing and monitoring side SolarCity has some growing up to do and unfortunately they’re not very interested in customer opinions, data, and suggestions but hopefully over time with a successful business they can improve in those areas.

I hope this post and series has been helpful. Let me know if you have any questions or thoughts in the comments below.

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