TOU revenue calculator

[J.P.M.]

Your approach to calculate revenue will work well for the very simple rate plans like SDG&E's EV-TOU-2 and DR-SES. The next generation of plans (like those of SCE and PG&E already) will be a bit more complicated, in which revenue and cost can not necessarily be calculated independently due to baseline credits or tiering on the *net* (SDG&E's TOU-DR plan is like this already).

In any case, the only way revenue can be compared to cost is if you re-calculate your cost under the new rate assumption... it is unlikely your cost under the DR plan would match your cost under DR-SES. To do this, you typically need access to past consumption on at least an hourly basis, if not 15 min. There may be programmatic ways to pull this from SDG&E with the right credentials, but otherwise you'll be counting on users to manually upload the necessary information.

I've just finished a spreadsheet to do a PV evaluation for a business on the AL-TOU plan. As you are programming you might also want to have some hooks in place to evaluated non-coincident demand and peak demand... not applicable to residential yet but probably will be eventually (maybe 10 years out?).

FWIW, +1

For SDG & E, DR-SES is pretty straight forward. Easiest approach for me was to start by treating generation as an asset and pricing out the production as revenue, separate from use and an expense. System revenue estimates are quite easy to do w/a spreadsheet. Annual expense is about as easy once the SDG & E download of usage is handled in 15 min. increments.

Depending on how much you believe your recent historical usage matches future usage, and how realistic long term estimates of annual system output from models like PVWatts might be, it's possible to see if/how much a system size can be reduced under current T.O.U. vs. tiered rates, at least for the simple tariffs. Also helpful to see if/how much time shifting of loads can do.

I suspect T.O.U can save money for consumers but probably won't as a practical matter because folks are clueless about how they're charged for power and anyway, don't want to reduce usage or go through the hassle of load time shifting.

In the end, the recent rate reform seems suspiciously silent (to me anyway) about any future control or direction of the times and durations of peak/off peak pricing periods, leaving the POCO's some freedom to shift peak times around as they see the need.

[sensij]

Your approach to calculate revenue will work well for the very simple rate plans like SDG&E's EV-TOU-2 and DR-SES. The next generation of plans (like those of SCE and PG&E already) will be a bit more complicated, in which revenue and cost can not necessarily be calculated independently due to baseline credits or tiering on the *net* (SDG&E's TOU-DR plan is like this already).

In any case, the only way revenue can be compared to cost is if you re-calculate your cost under the new rate assumption... it is unlikely your cost under the DR plan would match your cost under DR-SES. To do this, you typically need access to past consumption on at least an hourly basis, if not 15 min. There may be programmatic ways to pull this from SDG&E with the right credentials, but otherwise you'll be counting on users to manually upload the necessary information.

I've just finished a spreadsheet to do a PV evaluation for a business on the AL-TOU plan. As you are programming you might also want to have some hooks in place to evaluated non-coincident demand and peak demand... not applicable to residential yet but probably will be eventually (maybe 10 years out?).

[LDinSD]

Hi everyone.

As some on the forum have pointed out, the typical estimates of trying to offset total watts consumed vs. generated and determining system size is inaccurate for those on time of use and net metering rates. I decided to try and calculate my revenue generated based on time of use rates and power generation from hourly PVWatts estimations to determine how much revenue I would generate. The idea is to better determine the system size needed to offset what I actually spent annually. I know some on the forum have done this calculation (spreadsheets?) but have yet to hear of anyone coding this out. I went ahead and coded a calculator myself but want to make sure I am using the correct formula. Any input/corrections would be greatly appreciated.

Inputs
1) Hourly estimate of AC system output using PVWatts website which is based off my location and system size (export hourly csv file).
2) Net metering schedule and rate information. For example, month range:hour range:rate

Calculations
Multiply rate based on month, hour by watts generated and find the sum to get total revenue.

Once total revenue is generated, I can then compare to my annual electric cost to see if my system size is appropriate. Of course, net metering rates may change and the power companies are always looking to maximize profit, so this calculation is only appropriate for the rates entered. For example, in San Diego, SDGE is proposing to change peak hours from 4-10PM which changes my revenue $300-600 less annually depending on system size and orientation.

Finally, I'm toying around with the idea of throwing this up on a website for others to use as an additional reference/estimator. Would this be useful or is something already out there for this?

LDinSD