How Much Did I Save With Solar ? And will a Different Rate Plan Help?

I installed a 4.2kW solar system in late 2013, and spent a lot of time trying to quantify my cost savings. At the time, it was maddeningly hard because my data came from two difference sources (utility billing and solar inverter) and many billing plans are just plain complicated. A few months ago, I built out a billing calculator that utilizes Sense exported data to compute monthly billing costs for 95% of the residential public company rates in the OpenEI rates database, without solar and with solar. With that I was able to see my savings with a few caveats.

When I first installed solar in 2013, I was on a standard PG&E residential E1 tiered plan. With solar, I stayed on that plan, but moved to net metering (NEMS1). About 2 years ago I moved to the EV-A plan for EVs, though I already had several EVs and the plan had been around for a few years. The table below shows the comparison between those two plans, with (Full Usage) and without solar (Net Metering/ToU) given my exported hourly Sense data for the past year.

So it looks like my first move from non-solar to solar cut my bill by about 3K/year, offset by a 15K install cost back in 2013. But the second move, charging at night and moving to a ToU plan saved me an additional 5K/year. The caveats:

  • This is all done in terms of today’s rate plans, not “at the time” rate plans. Costs have gone up over time and there might have been other underlying changes.
  • I’m not really on the EV-A rate plan anymore, due to a variety of changes in both PG&E plans, plus my move to a Community Choice Aggregation energy supplier. But EV-A is still close to my current rate plan.

I would like to try this calculator against other users’ datasets and rate structures. I’m willing to run for a few Sense users as long as they:

  • Are willing to share their hourly export files for 2020 and potentially 2019 with me, along with info on their billing cycles. It’s probably best if you have data for a full year or more.
  • Have Sense solar - where’s the fun without the benefits of solar ?
  • Have a “from” and “to” rate plan that lives in the OpenEI rates database, or have rates that are similar. One of the most challenging things is entering rate tables, so I prefer to just pull them out of an existing database.
  • Are willing to post final results after collaborative checks and corrections

The final output would be a table like the one above, plus a comparison of your costs vs the world of other residential public company rates, like the chart below.

LMK via PM if you meet these criteria and are interested.

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