Tweet
A bit inconsiderate, maybe, but I think the discussion is still relevant to the OP and others have found it useful, so I'm not going to let it go just yet. If nothing else, this is a nice stress test for the TOU spreadsheet I made, which may be used by the OP or others for planning, and it is good to verify that the results make sense. It is also nice to have someone with actual knowledge contributing to the thread... I can run numbers and learn from them, but just don't have the experience to identify the corner points intuitively.
For example, since it was pointed out that W & S achieve energy parity at some high tilt angle, another good test case comes up. I find under the model conditions I've been running that this energy parity occurs near 78 deg tilt.
At 78 deg tilt, the annual TOU credit from EV-TOU2 (accounting for DST, weekends, holidays, etc), with the 12pm - 6 pm peak
South facing: $1123
West facing: $1290
With a 2 pm - 9 pm peak
South facing: $992
West facing: $1169
Finally, a result that mostly makes sense to me. When energy generation is equivalent, west does better than south since the production is better matched to the peak TOU period. The overall credits are lower than those discussed earlier because the tilt is too far from optimal, and less energy is generated. Shifting the peak later in the day penalizes south facing more than west facing ($132 vs $121), but the difference is smaller than I might have guessed.
I had started a TOU thread a couple months ago and can move any further posts on the subject there, if the OP prefers. As a discrete point, it might be fun to figure out at what tilt south facing and west facing achieve $ parity. More revealing would be a tilt / azimuth sensitivity analysis for some different TOU conditions, like I did in this post for PG&E (although in retrospect, I didn't account for DST in that post so there might be some inaccuracy there).
The value of this discussion, I think, is that people are trying to determine what system size and roof face makes sense under current plans, but also with an eye to the future and what the plans *might* become. Generally, for those who have projectable consumption that is a good fit for TOU, a smaller, more cost-effective PV system can be installed, especially if some educated guesses about the future can be made and the system can still be shown to make sense in that environment.
For example, since it was pointed out that W & S achieve energy parity at some high tilt angle, another good test case comes up. I find under the model conditions I've been running that this energy parity occurs near 78 deg tilt.
At 78 deg tilt, the annual TOU credit from EV-TOU2 (accounting for DST, weekends, holidays, etc), with the 12pm - 6 pm peak
South facing: $1123
West facing: $1290
With a 2 pm - 9 pm peak
South facing: $992
West facing: $1169
Finally, a result that mostly makes sense to me. When energy generation is equivalent, west does better than south since the production is better matched to the peak TOU period. The overall credits are lower than those discussed earlier because the tilt is too far from optimal, and less energy is generated. Shifting the peak later in the day penalizes south facing more than west facing ($132 vs $121), but the difference is smaller than I might have guessed.
I had started a TOU thread a couple months ago and can move any further posts on the subject there, if the OP prefers. As a discrete point, it might be fun to figure out at what tilt south facing and west facing achieve $ parity. More revealing would be a tilt / azimuth sensitivity analysis for some different TOU conditions, like I did in this post for PG&E (although in retrospect, I didn't account for DST in that post so there might be some inaccuracy there).
The value of this discussion, I think, is that people are trying to determine what system size and roof face makes sense under current plans, but also with an eye to the future and what the plans *might* become. Generally, for those who have projectable consumption that is a good fit for TOU, a smaller, more cost-effective PV system can be installed, especially if some educated guesses about the future can be made and the system can still be shown to make sense in that environment.
Comment