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Use your own meter data

If your utility offers Green Button, you can download a year of your own electricity use, hour by hour, and the rooftop calculator will run on it instead of on homes like yours. It's the most accurate way to use it. In my tests on 50 real homes, a home's own year landed within half a percent of an exact calculation; typical homes alone missed some households by more than 20%.

What you need

The dates to ask for: the 12 months ending yesterday. That's the latest full year your utility has, ending with the last complete day.

Downloading it

Menu names change now and then. If yours look different, look for "Green Button" or "Download my data" on your utility's usage page.

PG&E

  1. Sign in at pge.com.
  2. Under Usage and rates, choose View usage details.
  3. Choose Green Button: Download my data, near the bottom of the page.
  4. Choose the 12 months ending yesterday and the XML format.

PG&E sends a zip file, which may hold a gas file too. Choose the zip as it is: the calculator opens it and uses the electric file.

SCE

  1. Sign in to My Account at sce.com.
  2. On the left, choose Data Sharing & Download, then Green Button Download My Data.
  3. Choose the 12 months ending yesterday and the XML format.

SDG&E

  1. Sign in to My Energy Center at sdge.com.
  2. Open the Usage tab and choose Electric in the Meter menu above the graph.
  3. Click Green Button Download below the graph, choose the 12 months ending yesterday and XML, then Download.

Other utilities

Many utilities across the country offer Green Button downloads. Some, including APS, SRP, NV Energy and LADWP, offer only spreadsheet (CSV) downloads, which the calculator can't read yet. If that's you, tell me which utility; real files are what I need to add one.

Using it

In the rooftop calculator, under Household usage, choose Use my meter data and pick the file. The guided walkthrough asks for it too, when it comes to your household's use. Before anything changes, the calculator shows what it found: the dates, how often the meter read, kWh bought and sent back, and any missing days. Choose Use this year.

While it's in use, your yearly kWh comes from the file, and the usage pattern and heating questions are hidden, because your data already answers them. Future loads, a car, a battery and rate plans work as usual, on top. A missing hour is filled from the same hour on that month's other days; a missing day is covered by the month's other days.

If you already have solar

Your meter sees what you bought and what you sent back, but not what your panels supplied to the house directly. The calculator estimates that hour by hour from your existing system's yearly production and direction, which you enter under The solar you already own, and holds the year's total to what must be true: what the panels made, less what was sent back. Take the yearly production from your system's app or your installer if you can; it's the number that matters most here. If the file shows more sent back than that system could make, the calculator says the figure is probably too low.

What happens to your file

Your own browser reads it. It isn't uploaded or put in share links. It's kept in this browser tab so the rooftop and balcony calculators can both use it, and it's gone when you close the tab. Nobody else sees it, including me. More on the privacy page.

If it doesn't work