Rooftop Revolution: How To Get Solar To 100 Million Americans

by David Roberts, reposted from Grist

Get a load of this:

Nearly 100 million Americans could install over 60,000 megawatts of solar at less than grid prices – without subsidies – by 2021.

That’s from a new report by John Farrell at the Institute for Local Self-Reliance called “Rooftop Revolution: Changing Everything with Cost-Effective Local Solar.”

It’s about the spread of “solar grid parity” over the next 10 years, where grid parity is defined as “when the cost of solar electricity — without subsidies — is equal to or lower than the residential retail electricity rate.” People often talk about grid parity as if it’s some magic moment, but in fact it will happen in different places at different times, depending on local conditions and electricity prices. And it’s a moving target: It depends on how fast the cost of solar falls and how fast electricity rates rise.

Farrell says that the “installed cost of solar has fallen 10% per year since 2006 and grid electricity prices have averaged a 2% annual increase in the last decade.” In his projections, he uses 7 percent annual decline for solar costs and 2 percent for electricity increases, which seems conservative but reasonable. Obviously either of those rates could change, but almost everything I’ve read and heard predicts rising electricity rates; the rate of solar cost decline is somewhat harder to predict. As a technophile, my money is on the cost of solar falling faster than expected.

Anyway, given those assumptions, here’s a map that shows how and when solar grid parity will spread.

By 2021, some 100 million people in the top 40 U.S. metropolitan areas will be at grid parity for residential rooftop solar. The number is larger if you take into account people living outside those areas. It expands again if you assume widespread time-of-use pricing. And of course it expands a whole lot more if you include non-residential (commercial and industrial) rooftops. Like so:


Two big things to note about this:

1. Obviously this doesn’t mean 100 million people will have solar on their roofs in 2021. That’s just the cost-effective potential. To exploit that potential will require smart changes in policy. Farrell mentions several state laws and regulations — lower permitting fees, net metering, the like — but I want to emphasize his recommendations on subsidies.

Right now, there’s a federal solar tax credit of 30 percent that is set to expire in 2016. Tax credits are pretty crappy policy. They exclude the public sector and raise transaction costs to the point that tax credits are twice as expensive as cash grants. Keeping the solar tax credit perpetually in place would mostly enrich big solar developers … but dropping it abruptly would hurt the solar market.

The best option is to phase out the tax credit over time in favor of a less expensive policy responsible for 75 percent of the world’s solar PV and 45 percent of its wind power: feed-in tariffs. Feed-in tariffs — which apparently we’re now supposed to call CLEAN contracts (for Clean Local Energy Accessible Now) — pay people for creating clean energy and feeding it into the grid. If done right, CLEAN contracts could replace America’s entire tangled web of tax rebates, incentives, state mandates, and utility programs with something far simpler, more transparent, and more predictable. CLEAN money could phase out over time as costs drop, as is now happening in Germany.

We could exploit the full potential of solar, but that would require [gasp] planning, and planning is socialist, so oh well.

2. If 100 million people had residential rooftop solar, they’d still only be producing roughly 2 percent of the electricity consumed in the U.S. But electricity generation isn’t the only story here. That’s almost a third of the U.S. population!

That means a whole lot of voters — voters in Florida, Texas, Colorado, Arizona, Nevada — with direct experience being energy producers as well as consumers. They will come to understand the value of local, distributed energy in a tangible way and serve as a political force for its expansion. That’s what has happened in Germany. Smart energy policy doesn’t just create energy; it creates a constituency.

It can also be argued that locally owned solar has greater economic benefits (more jobs, spread more widely, and more money circulating in local economies) and greater benefits to the grid (avoided transmission, peak shaving) than absentee-owned power plants.

Energy policy is not just about numbers. It’s not even just about energy. It cannot be separated from economic development or social change. Energy democracy — local ownership, local benefits, local autonomy — ought to be an explicit goal of policy. In part that means planning ahead to take full advantage of solar’s extraordinary potential.

David Roberts is a staff writer for Grist. This piece was originally published at Grist.

28 Responses to Rooftop Revolution: How To Get Solar To 100 Million Americans

  1. Gingerbaker says:

    Do we still have a Department of Energy? Why don’t they start covering the Mojave Desert with panels? Then we could have 100% of our electricity needs taken care of with one fell swoop.

    I have seen a rough estimate of costs – if we had spent what we have already spent on the wars in Iraq and Afghanistan this would have been paid for already.

    We ought to have a checkbox on out tax returns. I check that I want my tax monies already earmarked for the military to go to electrical panels on the Mojave. A right winger can check that he wants his tax money currently going to the military to continue to go to the military. Nobody has to pay for something they don’t want.

  2. Mike#22 says:

    “If 100 million people had residential rooftop solar, they’d still only be producing roughly 2 percent of the electricity consumed in the U.S.”? Not sure of the assumptions being used, but I would say:

    If 100 million people had residential rooftop, that would be roughly 40 million systems (at 2.5 people per household), each averaging more than 5,000 kwh/year (closer to 8,000 kwh/year for average systems around here in Philadelphia), that is 200 billion kwh or 5% of the nations 4 trillion kwhs. Then add in the potential for non-residential installations, just as cost effective, and its up to 10%.

  3. Yvan Dutil says:

    Without smart grid, this is a good strategy to wipe out the electrical network.

  4. Leif says:

    There is a GOP president here, they do not pay for Abortion. Why should my tax money pay to hasten the end of civilization and the severe disruption to Earth’s Life Support Systems that I strenuously disapprove of?

  5. Hot Rod says:

    ‘If 100 million people had residential rooftop solar, they’d still only be producing roughly 2 percent of the electricity consumed in the U.S.’

    doesn’t sound so exciting to me!

  6. Mark Shapiro says:

    You mean “precedent”.

    Unfortunately, it’s a bad precedent. As much as I agree with the sentiment, the notion that individuals control their tax dollars is actually anti-democratic when you think about it. Government policies -taxing and spending – are collective. period.

    The only solution is to make good policies.

  7. Leif says:

    Yvan: The smart grid is part and parcel of the Green Awakening Economy. (More Jobs). However, first and foremost, “We the People must stop the accumulation of profits from the pollution of the commons. I can imagine only about 1% of the population that would be against this action. It does appear to be a damn poor foundation to base an economy on and I believe history will testify to that fact!

  8. Leif says:

    The longest journey begins with a single step. To this point we have taken but a small shuffle. Get all pulling in the same direction I suspicion you will swallow your gum Hot Rod.

  9. Mark Shapiro says:

    PV panels at $1 per Watt is the biggest clean energy success story of my lifetime.

    Too bad it’s invisible.

    What hides this success is our voluntary thrall to AC on the grid. We can’t imagine using PV without first converting it to AC, then converting it back to DC to run our most valuable tools: electronics.

    PV produces DC and only DC. Electronics use DC and only DC. ClimateProgress is written on an electronic device powered by DC and we read every word on DC-powered devices.

    Can’t PV and electronics just get along?

  10. Hot Rod says:

    Grid parity in 9 years, based on solar falling 7% per annum, then 1/3 population install solar, and it’s still 2% (based I hope on some ever-increasing consumption rather than today’s consumption) – just didn’t seem much of a wedge to get excited about on CO2 grounds. Particularly if you want to electrify transport.

  11. Barry saxifrage says:

    homes use 39% of usa electricty, or 1,500 billion kwh. So 200 billion kwh from rooftop solar pv would cover 13% of home electricty. Add in solar thermal and efficiency and the numbers are getting high enough to get rid of a lot of coal.

  12. Barry saxifrage says:

    Homes in usa use 200 billion kwh for lighting. Lightbulb regs and leds could cut that sharply. Pv +LED might get us 20% of home electric

  13. catman306 says:

    Yes, and inverters waste energy which is cast away as heat.

    Recreational Vehicles (RVs) use 12 volt appliances that include everything you have in your home. Solar panels produce 12 volts as a standard.

    Build rooftop solar, off the grid, powering your RV style appliances.

    You’ll need batteries for nighttime use.

    Google “12 volt appliances” 9 million hits

  14. Ron Broberg says:

    I installed 500W last year and will install another 500W this year as a DIY project. Just ‘cuz.

  15. adelady says:

    Feed-in tariffs can be a huge advantage for non-domestic users. A church or a school or a sports stadium can look at the feed in tariff as a straightforward investment option. Any commercial or non-commercial enterprise that has low or intermittent power use under a large expanse of roof would be well advised to put limited funds available for investment into a decent sized PV system.

    It will pay for itself in not many months, esp structures like warehouses with no a/c, and provides a reduced operating cost base – forever. These benefits are either unavailable or hopelessly complex under a tax rebate system for non-taxpayers, eg schools & churches, or strange offsets/ depreciation allowances for commercial enterprises.

  16. Mark Shapiro says:

    RIght. AND – if this 12V (or 24V) could be standardized so that more homes had it and appliances were built with this option, it could grow tremendously. It would be a virtuous circle.

    How to start this?

  17. Lewis Cleverdon says:

    2% of power demand, or even 13% of power demand, from rooftop solar seems anything but exciting, given :

    a/ – the need for massive additional power supply for trams and electric cars and railways, etc., and
    b/ – the plain fact that any fossil fuels locally displaced by renewables are being bought and burnt elsewhere.

    So why the constant focus on the secondary (or tertiary ?) issue of non-fossil power supply ?

    So when are Americans going to get excited about demanding that the US government accede to an equitable and efficient global climate treaty ?



  18. Hot Rod says:

    Also be careful extrapolating price falls from the last two years. Production capacity has diverged from global demand hugely, most of the fall imho has been that factor as firms sell at anything above cash cost. Look at share prices of Renesola, First Solar, Solarworld – all down 80% in 12 months. It’s more that than Moore’s Law. The current price is certainly not sustainable for the producers.

  19. Todd says:

    There have been a flood of news releases of breakthrough PV innovations and significant incremental improvements in existing products the last few months. If even only a few of them succeed, this will accelerate the growing competitive advantage of PV. But what I expect to really give PV the lead is a continued water crisis in large regions of the US. This will force a significant number of thermal power plants to shut down, either for significant periods or more or less for good, for lack of cooling water for their steam turbines. Only then will we fully appreciate the value of water-free, carbon-free sources of electricity. Distributed PV will fit very well in this scenario.

  20. Dennis Tomlinson says:

    The efficiency of modern AC inverters and DC converters are both north of 90%. A loss? Yes. Converted to heat? Yes. Room for improvement? Always. But the DC distribution of electricity is an argument Edison lost to Steinmetz back in the late 1800’s, and with good reason. The resistive losses of any practical gauge of copper wire over any significant distance was prohibitive then, still prohibitive now, and will remain prohibitive pending the practical implementation of superconductors. The advantage of distributing AC is realized by transforming it up to very high voltages for long-haul distribution, then transforming it down to lower AC voltages for local distribution. Transformer efficiencies are also 90%+. And since power is the product of voltage and current, transmission at significantly higher voltages also means significantly lower currents. The resistive losses in copper wire are proportional to current – not voltage. Therefore, it is a necessity to use high voltage AC on the grid. Fortunately for Edison, Steinmetz was a GE employee – not a Westinghouse employee. By the end of the 19th century, Steinmetz had designed distribution systems using 3-phase AC, realizing even greater efficiencies. Nowadays, almost no one has heard of Steinmetz, except for the folks around Schenectady (the first city he wired), or Chicago, where a high-school is named after him.

  21. Dennis Tomlinson says:

    Oops… correction. Meant to say: resistive losses in copper are proportional to ‘the square of’ current – not the voltage.

  22. Gingerbaker says:

    I’m thinking it would be orders of magnitude more important to accomplish the very important goal, by appealing to Republican anti-tax sentiment, than to reject such a plan based on a highly debatable definition of ‘democracy’.

    Please notice that we already have had check boxes for (much smaller) earmarked allocations on our tax returns.

  23. Gingerbaker says:

    Hence my suggestion that we get 100% of our power needs, forever, by having a national energy project to cover the Mojave with collectors.

    Way more efficient to pre-assemble arrays and ship them for ground installation instead of custom-fitting them onto roofs.

    Supposedly, we could have paid for this already for what we spent for wars in Mesopotamia the past ten years. Since the power comes from sunlight, for free, and tax dollars pay for the infrastructure, I don’t see why the resulting AC power should not be free to the consumer.

  24. Todd says:

    01.31.2012: Siemens HCPV module partner Semprius achieves world record for photovoltaic module efficiency

    DURHAM, N.C. Semprius, Inc., an innovator in high concentration photovoltaic (HCPV) solar modules, has set a new world record for photovoltaic module efficiency, reaching 33.9 percent (active area). The module was tested indoors at Standard Test Conditions (850 W/m2, 25 degrees C cell temperature, and a spectrum matched to AM1.5D) by the Instituto de Energia Solar at the Universidad Politecnica de Madrid (IES-UPM). This efficiency result, certified by the IES-UPM and corroborated by outdoor measurements made at the Institute of Concentration Photovoltaic Systems (ISFOC) in Puertollano, Spain, significantly exceeds the previous claim of 32.0 percent. Semprius delivers a unique HCPV module design that begins with its proprietary micro-transfer printing process. This process enables the company to fabricate the world’s smallest solar cell – approximately the size of a pencil point – to create solar modules with unmatched efficiency and performance. Semprius’ proprietary micro-transfer printing technology enables CPV modules constructed from a large array of very small gallium arsenide-based, multi-junction solar cells. Module cost is minimized by using high concentration ratio. Inexpensive optics concentrate 1,000 suns onto the high-efficiency solar cells, which only cover 0.1% of the module area.

  25. Todd says:

    2012-03-13. New Hampshire, U.S.A: Twin Creeks Unwraps New Tool, Process to Slash Silicon Solar PV Costs
    By James Montgomery, News Editor,
    A start-up company has emerged from stealth mode with a new technology that promises to radically change the game for silicon solar photovoltaics (PV) manufacturing, by taking out almost all the starting material and up-front process costs.
    For silicon-based solar PV manufacturing, costs on the materials alone (silicon, process gases, silver paste, encapsulants, etc.) can be $0.60/Watt. One dollar per watt for solar, fully installed, is held up as the ultimate grid-parity goal — but that’s still a long way off, and costs have to come down a lot more both in manufacturing and balance-of-systems. Some companies have figured the best way to reduce costs is by using less starting material. Today’s conventional silicon-based solar PV manufacturing still means sawing silicon ingots into wafers 150 to 200 microns thick. This creates issues of kerf loss (material lost as sawdust from sawing ingot into wafers) and wafer fragility, and requires the need to prep the new wafer’s surface for following solar-cell creation steps.
    Today, Twin Creeks Technologies has de-cloaked its technology called “proton induced exfoliation.” Twin Creeks’ tool, dubbed Hyperion, shoots hydrogen atoms into a thick piece of silicon at high current and high voltage where they embed at a fixed depth and form micro-bubbles; when heated, a layer of material is cleaved off. (The hydrogen atoms [protons] aren’t preserved in the lattice structure of the silicon so there’s no damage.) The result is a super-thin 20-micron skin of silicon, created with zero kerf loss, and reducing by 90 percent the amount of silicon content processed. “All you really need is under 30 microns” of silicon material for current collection; the rest is mainly for mechanical support and no longer necessary.

  26. Todd says:

    February 02, 2012. MiaSole Producing Thin-Film Solar Panels With 14% Efficiency
    By Christopher Martin (Bloomberg

    MiaSole Inc., a closely held manufacturer of thin-film solar products, is producing panels in volume that convert 14 percent of the energy in sunlight into electricity. MiaSole’s conversion efficiency rates have increased by more than 30 percent in the past year, the Santa Clara, California-based company said today in a statement. MiaSole expects the average efficiency of its panels to hit 15 percent later this year, and at 14-15 percent, the startup’s solar panels are entering the efficiency territories of silicon solar panels out there. That means if it can sell its panels for less, than it’ll be a break out player.
    That’s higher than the 12.4 percent average efficiency that First Solar Inc., the world’s biggest thin-film solar company, reported for the third quarter. MiaSole sells panels with a layer of a copper-indium-gallium-selenide compound sandwiched between sheets of glass.
    Increasing electricity output from each panel reduces the price of the power, which helps solar compete against energy derived from lower-cost fossil fuels. MiaSole has reached 17.3 percent efficiency in a lab.

  27. Speedy says:

    Low voltage DC is the least valuable form of electricity. Building a parallel LVDC grid, even just inside each house, would be a waste of money. A 10A 12V circuit can only deliver 120W, while requiring ~20x cable thickness of a 10A 230V circuit, which can deliver 2,3kW, in order to get the same relative power loss.

    You seem to forget that low-power appliances, where LVDC could be useful, only account for a miniscule fraction of the overall electricity use.

  28. J4zonian says:

    The check box on election spending was a widely agreed-on plan whose main purpose was to forestall effective campaign spending curbs or other ways to keep the rich from controlling elections. It does little and stops much. Earmarking money allows the rich to continue to control politics and the world with it. It’s time to stop that. We need real changes, not fake ones that function to distract and mollify people.