1. Was it worthwhile? Where have the benefits of rooftop solar photovoltaic generation exceeded the cost?
Dr. Parth Vaishnav
Dr. Nathaniel Horner
Prof. Inês Azevedo

2. Motivation
Have historic rooftop solar PV installations, in aggregate, paid off?
Under what circumstances does installation of a current system pay off?
How are the subsidies – rebates, grants, and federal investment tax credits – distributed among counties with different median incomes?

3. Evolution of benefits over time - EASIUR

4. Evolution of benefits over time – AP2

5. x ( + ) Benefits AP2 EASIUR CEMS NREL TMY3 data
LBNL dataset of installed systems (560k systems)
Marginal benefits based on Siler-Evans et al.
Summed for each year of a system’s 20-year life
Electricity generated
x (
Electricity price +
Environmental benefits )
Consumption displaced
Electricity sold back to grid
LMP
Retail price
Commercial and Residential Hourly Load Data (NREL)

6. x Cost to consumer Cost to consumer Federal ITC Deflator
Total installed price
Rebate

7. + x - x Cost to public Federal ITC Rebate Deflator
Summed for each year of a system’s 20-year life
Retail price -
LMP x
Electricity sold back to the grid

8. System owners recover costs if they receive the retail price for all electricity sales
(Using a 7%pa discount rate)

9. Air quality and climate change benefits are smaller than the federal ITC and rebates
(Using a 2%pa discount rate)

10. At current prices, installed base would have cost <$1b less
Barbose, G., Darghouth, N., Tracking the Sun VIII: The Installed Price of Residential and Non-Residential Photovoltaic Systems in the United States. Lawrence Berkley National Lab.
Don’t show line for EIA installed capacity

11. Public benefit < cost in all cases
For current systems, private benefit > cost in CA, CT, NV, NY, TX assuming retail price
Private benefits and costs discounted at 7%; public at 2%
Public benefit < cost in all cases

12. Significant within-state diversity in current per-kW annual costs and benefits

13. Significant within-state diversity in current per-kW annual costs and benefits
Public net benefits
7% discount rate
2% discount rate

14. Subsidies go to richer counties
Subsidies go to richer counties. Distribution of rebates is getting closer to that of population

15. Conclusions Systems are cheaper now
But the grid is cleaner also
Air quality and greenhouse gas benefits exceed value of subsidies
Private consumers only break even at low discount rates or if they receive the retail price for sales to the grid
Systems and rebates have flowed to richer counties
Encouraging community solar could help
Net metering policy should be tuned to account for benefits and costs of solar

16. Acknowledgement
This work was supported by the center for Climate and Energy Decision Making (SES ), through a cooperative agreement between the National Science Foundation and Carnegie Mellon University