An Analysis of California’s
Million Solar Roof Initiative
Dennis Silverman
Department of Physics and Astronomy
U. C. Irvine
Conclusions






We will show here a basic cost analysis of the million
solar roof plan.
We will find that the total installation cost will be $20
billion.
The total output from those roofs on average will be
about half of that of a single nuclear reactor.
Compared to a $1-$2 billion cost of a nuclear reactor,
California could build 10 nuclear reactors, for the same
money.
The new nuclear reactors would boost nuclear from 13%
of California’s power to 35% on peak power days.
Along with 19% of hydro power, and 20% of solar and
wind power, California could have 74% pollution free and
CO2 free power from the same amount of money that
will be flagrantly wasted on the million solar roof plan.
Cost of Building the Million Solar
Roofs



The typical photovoltaic solar roof being
considered is 3 kilowatts (kW).
The cost of such an installation with an
inverter to the electric grid is $20,000 for
panels and $26,000 for integrated roof
panels.
Multiplying the $20,000 by a million gives
the total cost to $20 billion.
How much power is generated?








The 3kW installation times a million solar roofs is 3,000 megawatts.
But wait, that is “peak power” when pointed directly at the sun.
A rooftop installation does not track the sun and is not at the
optimal angle for noontime power other than one day a year.
Other problems: roof slope not at latitude angle, nighttime,
seasons, clouds, and the marine layer (June Gloom).
The “average power” is only 1/5 the installed and paid for “peak
power”.
Therefore the average power generated by the million solar roof
installations will be 600 megawatts.
That is about half of that of the 1,100 megawatts of a nuclear
reactor.
It is also only 1.2% of California’s maximum power usage of 51,000
megawatts.
Comparison to other energy
systems







In Victoria Australia, they are installing a solar photovoltaic system
with sun tracking multiple mirrors on a few, more efficient solar cells
(solar concentrator).
The cost of this per kW is half that of the cheapest home rooftop
systems.
Even cheaper, large solar concentrator (mirror) systems that heat
mineral oil or sodium come close to the cost of commercial
electricity.
Faced with a choice, PG&E chose the solar concentrator system to
be 1/3 to ¼ the cost of solar photovoltaic.
Since most homes will be connected to the electric grid, and draw
most of their power from it, what is the point of building your own
more expensive system?
Also, grid electricity will be 2/3 greenhouse gas free in California by
2030 if goals are achieved.
Bragging rights? Feel good? The rugged hunter gatherer? The
provider of fire? The survivalist instinct? Getting a free subsidy
from the abstract “government”?
But you forgot about the rebates!



I have never yet heard from solar vendors,
environmental groups or self-satisfied
home or business installers any concern
for who pays for the rebates.
It is taxpayers, and to some extent utility
users.
In this analysis we will analyze the total
costs to all involved.
Cost of the embedded roof panels
and rebates.







For the 3kW installation the cost is $26,000.
The million solar roof rebate is $8,400.
The federal tax rebate is capped at $2,000.
So the cost to the buyer is $15,600.
Not only will the buyer be getting mostly free
electricity, but the installation will add to the
value of his/her home.
Thanks for the $10,400 gift.
The million solar roof bill is only for about $3
billion, so later installations will get less state
rebate.
Nobody was buying?





The original bill required the user to pay for electricity
based on the rate for the hour of use. This was costly.
The new amendment has them pay only the standard
overall rate.
However, the original pricing scheme was put in to show
some economic sanity and competitiveness.
Solar cells generate electricity during the day when there
is less demand, and give a lot of it to the grid.
Then at evening when demand is highest (and so is
cost) the user takes the bulk of power from the grid,
now without paying extra.
But after installation the power is
free!




First of all, the solar panels have to be kept clean. In
many locations this would mean a weakly washing
involving lots of water from hoses onto rooftops, and the
labor of a million homeowners.
Maintenance of a million home electric installations has
to cost more than in a centralized plant.
The economic analysis by vendors shows a profit to
homeowners, based on the historical 6.7% increase per
year in the cost of electricity.
In writing off the energy and pollution cost of creating
the silicon solar cells, estimates vary from 1-2 years of
the system’s power, to that of generating ½ the
greenhouse gases of natural gas on a lifetime basis.
Costs to other Utility users




Part of the rebates are being funded by extra utility
charges.
While homeowners installing solar cells may only need
25% of their power from the utility, they will only pay
25% of their previous bill, since most costs are
proportional to usage.
However, a large part of the bill for most users is the
cost of delivery, not the power. That means the costs to
construct, upkeep, and run the grid and the link to the
homeowner.
Why should the cost of the grid be cheaper to the solar
cell home? In fact, they use the grid both ways, in
sending power to the utility during the day, and drawing
as much power as anybody during the night.
But what about passive solar
adaptation?




Usually one would keep a house cool by
providing shade.
With solar cells on the most solar exposed part
of the roof, the house would heat up if they
were embedded in the roof.
The house would also heat more if the
embedded tiles are non-reflecting, and used to
replace more reflective roof tiles.
Solar panels might take the place of cheaper
and more useful solar water heating, which
cannot take place far from the home.
How much free power do I get?




A 3kW peak system with the 1/5 average power
generates 3/5 kW = 600 W average power.
Multiplying by the approximately 9,000 hours in
a year, this is 5,400 kWh (kilowatt hour) per year
of energy.
The average household use is 84,500 million
kWh / 11.5 million households, or 7,350 kWh per
year.
So a PV solar system on an average household
would account for 5400/7350 = 73% of the
power.
How long until payback?






The 7,350 kWh per year at 13¢/kWh will normally cost
about $956 per year (this is $80/month).
If 73% of that is rooftop generated, it will save the
homeowner $956 x 0.73 = $700 per year.
If the installation is the cheaper $20,000 panels,
payback to society will be in 29 years.
For the more expensive embedded panels at $26,000,
payback to society will be in 37 years.
Using the price to the above homeowner with the rebate
of $15,600, the payback to him/her will be in 22 years.
From radiation damage to the panels, thirty years is
about their lifetime.
Monetary alternatives?




I apologize that I am not an economist to do the
interest rate calculations to evaluate this long
term.
A US government analysis only showed the
payback for California to be in the 20—50 year
range.
However, most installers want to be paid on
completion of the job, not over 20-30 years.
The $26,000 in the bank at a 4.5% interest rate
would yield $1170, more than enough to pay the
$956 yearly electrical bill.
Cost Effective Alternative Solar Power




PG&E in Northern California decided on a large scale
solar thermal facility heating a liquid which then
vaporizes water and runs a turbine. The cost of that
system is to be 1/3 to ¼ the cost of solar photovoltaic
for the same power.
While the grid can distribute solar generated electricity,
there is no way to distribute hot water to households.
Here, solar hot water heating at a much cheaper cost of
$3,000 - $5,000 per household can eliminate 50% to
80% of your water heating energy.
Household water heating takes comparable energy to
the household electricity usage.
Conclusions






We have shown here a basic cost analysis of the million
solar roof plan.
We found that the total installation cost will be $20
billion.
The total output from those roofs on average will be
about half of that of a single nuclear reactor.
Compared to a $1-$2 billion cost of a nuclear reactor,
California could build 10 nuclear reactors, for the same
money, generating 11 gigawatts of power.
The new nuclear reactors would boost nuclear from 13%
of California’s power to 35% on peak power days.
Along with 19% of hydro power and 20% of utility solar
and wind power, California could have 74% pollution free
and CO2 free power from the same amount of money
that will be flagrantly wasted on the million solar roof
plan.