Going Solar - Analysing my energy usage

Part I - Planning to add solar panels to my roof, I started with an initial analysis of my electricity consumption pattern.

My old house had a solar pool heater covering the roof. It was relatively new and sturdy – it seemed a shame to rip it out for what was then this new fangled solar panel stuff. But recently, I moved to another house and the idea of solar panels was now becoming an obvious choice. Still, it took a year before I decided to explore it. A brand spanking new smart meter had been installed just days before I moved in.

The smart meter is an EDMI Atlas Mk10D. From what I can tell, it is a 3 phase smart meter that can also handle net metering once the solar panels start feeding power back to the grid. It has an antenna to send the data back to base. With the frequent usage record, it allows me (forces me?) to have a time of usage tariff. The fact that I can spy with my eagle eye, a set of three fuses in the top corner confirms that I have a 3 phase supply. This means I should be able to have a solar panel array exceeding 5 KW.

I had taken an electricity plan from AGL. After the year had passed, I checked the AGL website and was delighted to find a downloadable version of the smart meter readings.

I don’t remember seeing that before. Several queries before, on the phone, had disappeared down the we-will-get-back-to you-or-stuff-will-be-mailed-emailed-to-you runaround. The file was in CSV format. Besides several obscure fields, it has the start and end of 30 minute intervals and the consumption for that period. So I had about a year’s worth of data in 30 minute chunks.

The columns in the file are:

• AccountNumber Your account number and appears on your bill
• NMI Your National Meter Identifier and appears on your bill
• DeviceNumber Meter number and this should be on the label on your smart meter
• DeviceType, RegisterCode No idea! But any solar feedin line has a different code.
• RateTypeDescription Always set to Peak even though I am on a time-of-day tariff. Update: Once solar feedin starts, there is one line for solar feedin for each interval and this field is set to Solar.
• StartDate The start of the 30 minute interval as a date and time (e.g. 1/09/2017 17:30)
• EndDate The end of the 30 minute interval as a date and time (e.g. 1/09/2017 17:59)
• ProfileReadValue The all-important usage in KWh
• RegisterReadValue No idea. Always 0. Is this the feedin part? Or does the previous field go negative? Can't wait! Update: Still 0. Extra line for solar for each interval, even if 0. ProfileReadValue is always positive.
• QualityFlag No idea - always A. Might be a good thing too.

That was way too much data to crunch and I could not find a source on the web that gave the corresponding solar output for the same period at 30 minute intervals. So I summarised the data into 1 hour intervals on a monthly basis. This allowed me to look at the consumption by time of day as well as across seasons.

The seasonal consumption over a year was all over the place. I applied a trend line of about 255 intervals (the max I could use) or a little over 5 days. The consumption across seasons showed that it was higher during the winter months. A prolonged dip towards the end of the year was probably when we were on vacation. There was a jagged edge with a period of about a fortnight that I can’t explain.

The consumption over the course of the day was a bit interesting. If you go to work during the day and the house is empty then, the power consumption has a small peak in the morning as you get ready and then flattens out. After that, you get a spike in the evening between 6 PM and 10 PM when everyone gets back home. But I work from home most days and so I have a peak in the middle of the day. There is also a second peak later in the day. This was markedly higher during winter. This makes sense as heating is turned on once the sun is down during winter.

With most of my usage being in the middle of the day, the solar panels would really help as that is when they put out the most power. The second peak, especially in winter, will happen after dark and cannot be addressed. Even use of a storage battery would be only marginally effective. What might work is moving some of the usage towards the middle of the day.

In the next blog I will look at the numbers for a solar panel setup on my roof.