ERCOT RE News SAWG Rooftop PV Forecast & W TX HVDC Transmission Line Option


Electric Reliability Council of Texas Renewable Energy News: Supply Analysis Working Group Rooftop Photovoltaic (Solar) Forecast and High Voltage Direct Current Transmission Line Option in the Long-Term West Texas Export Study Report

1) Rooftop PV Forecast: Slide 9

“- An hourly rooftop PV forecast was created
- A forecast was created for residential ESIIDs using the load profile assignment for each weather zone
- Total installed capacity was approximately 1,030 MW as of September, 2021
- Forecast is for the total installed capacity to increase to approximately 6,000 MW by August, 2031
- The gross forecast minus the rooftop PV forecast results in the net forecast”

Ref: “2_SAWG_2022 Long_Term_Load Forecast_1-12-2022.pptx”, slides 9 – 14:


My comments:

My points in posting this are to show that ERCOT is working on rooftop PV forecasting, and to show the scale of the increase they are looking at in this particular case.


One way to look at this is: 6,000 / 1,030 over 10: years = increase of 19.3% each year (assuming the same % increase each year & not taking into account what happens after 2031).

Increase in 2022 would be 198 MW; in 2031 it would be 969 MW.

Units are actually MWac, which is typically 70 to 80% of the typically quoted system “nameplate” size in MWdc: example = 30 modules at 300 W/module = 9 kWdc = typically 6.3 to 7.2 kWac. Using this example, the increase in 2022 would be about 28,000 to 31,000 homes.

2) Long-Term West Texas Export Study Report: Pg 14:

Table 4: Reliability and Economic Results Summary:
Improvement Option 2 (3 AC lines + 1 HVDC) has a TSP cost estimate of $5,203 M compared to Option 1 (4 AC lines) at $2,738 M & Option 3 (5 AC lines) at $3,459 M.

Ref: “Long-Term West Texas Export Study Report”:


My comments: My points in posting this are to show that ERCOT is indeed looking at HVDC transmission line options; that they are expensive; and that the cost/benefit analysis is complicated.

Also, the reason they are looking at this is that there is a forecast for large increases in Wind & Solar generation and this creates problems for the transmission system both due to the amount of energy that needs to flow from West Texas to where it is used and due to complications due to the differences in Wind & Solar generation sources (Inverter Based Resources or IBR) and traditional thermal generation sources (natural gas, coal, & nuclear).

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