A solar economics spreadsheet


In light of my recent threads on CitizenRe I built a spreadsheet to do solar energy economic calculations. If you click on that, you can download the spreadsheet to try for yourself. If you don't have a spreadsheet program (I recommend the free Gnumeric or Open Office) it's also up as a Google Solar Spreadsheet but you may need a Google account to plug in your own numbers. The sheet shows the key numbers you will play with in blue. Rebates and incentives vary a lot state to state. The federal tax credit is hugely different if a corporation puts up the panels instead of an individual homeowner. The sheet lets you enter your price for grid power but doesn't yet include a way to code it so that this price rises or falls with time.

The sheet will tell you a couple of interesting numbers. One is, based on a solar cost, what that works out to as a price per kwh. You can see from that how much more or less solar costs than grid. Alternately, for setups where the solar does cost less than grid, it calculates how many years it takes for the solar installation to "pay for itself." Of course, at today's prices, the systems never pay for themselves compared to grid, but this lets you play with the numbers and find out where it will.

I've set things for some California rules, including 12.8 cents/kwh and a $2.50 per watt rebate. Rebate rules vary greatly from state to state, you can find them at this web site.

Some things you can learn

  • It doesn't really matter if you try to amortize the panels over 30 years or 50. Beyond about 25, it works out to the same. I have a box where you can guess a value for the panels at the end of the period, but it doesn't change things a lot.
  • Compared to 12.8 cent grid power, you need an after rebate fully installed cost of about $2.75/watt to match, which can come with $2.70 for panels and $3/watt, for a residence.
  • Compared to the national 8 cent price you need an installed price of about $1.90. Or $1.70 in a state with less insolation.

Let us know what other things you learn, or if you want to improve the sheet with variable grid cost and adding other credits and costs (I list what's not factored) let me know.

Update: A commenter pointed us at this calculator which factors in tax consequences. They make a much bigger difference than I expected. For homeowners, they factor in the fact that interest from a home equity loan is tax deductible, even though power from the power company is not. For corporations, the quick write-off of the panels also makes a bigger difference than my intuition suggested. Alas, this page does not appear to work in firefox on linux.



In order to insure energy and economic independence as well as better economic growth without being blackmailed by foreign countries, our country, the United States of America’s Utilization of Energy Sources must change.
"Energy drives our entire economy.” We must protect it. "Let's face it, without energy the whole economy and economic society we have set up would come to a halt. So you want to have control over such an important resource that you need for your society and your economy." The American way of life is not negotiable.
Our continued dependence on fossil fuels could and will lead to catastrophic consequences.

The federal, state and local government should implement a mandatory renewable energy installation program for residential and commercial property on new construction and remodeling projects with the use of energy efficient material, mechanical systems, appliances, lighting, retrofits etc. The source of energy must be by renewable energy such as Solar-Photovoltaic, Geothermal, Wind, Biofuels, Ocean-Tidal, Hydrogen-Fuel Cell etc. This includes the utilizing of water from lakes, rivers and oceans to circulate in cooling towers to produce air conditioning and the utilization of proper landscaping to reduce energy consumption. (Sales tax on renewable energy products and energy efficiency should be reduced or eliminated)

The implementation of mandatory renewable energy could be done on a gradual scale over the next 10 years. At the end of the 10 year period all construction and energy use in the structures throughout the United States must be 100% powered by renewable energy. (This can be done by amending building code)

In addition, the governments must impose laws, rules and regulations whereby the utility companies must comply with a fair “NET METERING” (the buying of excess generation from the consumer at market price), including the promotion of research and production of “renewable energy technology” with various long term incentives and grants. The various foundations in existence should be used to contribute to this cause.

A mandatory time table should also be established for the automobile industry to gradually produce an automobile powered by renewable energy. The American automobile industry is surely capable of accomplishing this task. As an inducement to buy hybrid automobiles (sales tax should be reduced or eliminated on American manufactured automobiles).

This is a way to expedite our energy independence and economic growth. (This will also create a substantial amount of new jobs). It will take maximum effort and a relentless pursuit of the private, commercial and industrial government sectors’ commitment to renewable energy – energy generation (wind, solar, hydro, biofuels, geothermal, energy storage (fuel cells, advance batteries), energy infrastructure (management, transmission) and energy efficiency (lighting, sensors, automation, conservation) (rainwater harvesting, water conservation) (energy and natural resources conservation) in order to achieve our energy independence.

"To succeed, you have to believe in something with such a passion that it becomes a reality."

Jay Draiman, Energy Consultant
Northridge, CA. 91325
Feb. 26, 2007

P.S. I have a very deep belief in America's capabilities. Within the next 10 years we can accomplish our energy independence, if we as a nation truly set our goals to accomplish this.
I happen to believe that we can do it. In another crisis--the one in 1942--President Franklin D. Roosevelt said this country would build 60,000 [50,000] military aircraft. By 1943, production in that program had reached 125,000 aircraft annually. They did it then. We can do it now.
"the way we produce and use energy must fundamentally change."
The American people resilience and determination to retain the way of life is unconquerable and we as a nation will succeed in this endeavor of Energy Independence.

The Oil Companies should be required to invest a substantial percentage of their profit in renewable energy R&D and implementation. Those who do not will be panelized by the public at large by boy cutting their products.

Solar energy is the source of all energy on the earth (excepting volcanic geothermal). Wind, wave and fossil fuels all get their energy from the sun. Fossil fuels are only a battery which will eventually run out. The sooner we can exploit all forms of Solar energy (cost effectively or not against dubiously cheap FFs) the better off we will all be. If the battery runs out first, the survivors will all be living like in the 18th century again.

Every new home built should come with a solar package. A 1.5 kW per bedroom is a good rule of thumb. The formula 1.5 X's 5 hrs per day X's 30 days will produce about 225 kWh per bedroom monthly. This peak production period will offset 17 to 2

4 cents per kWh with a potential of $160 per month or about $60,000 over the 30-year mortgage period for a three-bedroom home. It is economically feasible at the current energy price and the interest portion of the loan is deductible. Why not?

Title 24 has been mandated forcing developers to build energy efficient homes. Their bull-headedness put them in that position and now they see that Title 24 works with little added cost. Solar should also be mandated and if the developer designs a home that solar is impossible to do then they should pay an equivalent mitigation fee allowing others to put solar on in place of their negligence. (Installation should be paid “performance based”).

Installation of renewable energy and its performance should be paid to the installer and manufacturer based on "performance based" (that means they are held accountable for the performance of the product - that includes the automobile industry). This will gain the trust and confidence of the end-user to proceed with such a project; it will also prove to the public that it is a viable avenue of energy conservation.

Installing a renewable energy system on your home or business increases the value of the property and provides a marketing advantage. It also decreases our trade deficit.

Nations of the world should unite and join together in a cohesive effort to develop and implement MANDATORY RENEWABLE ENERGY for the sake of humankind and future generations.
The head of the U.S. government's renewable energy lab said Monday (Feb. 5) that the federal government is doing "embarrassingly few things" to foster renewable energy, leaving leadership to the states at a time of opportunity to change the nation's energy future. "I see little happening at the federal level. Much more needs to happen." What's needed, he said, is a change of our national mind set. Instead of viewing the hurdles that still face renewable sources and setting national energy goals with those hurdles in mind, we should set ambitious national renewable energy goals and set about overcoming the hurdles to meet them. We have an opportunity, an opportunity we can take advantage of or an opportunity we can squander and let go,"
solar energy - the direct conversion of sunlight with solar cells, either into electricity or hydrogen, faces cost hurdles independent of their intrinsic efficiency. Ways must be found to lower production costs and design better conversion and storage systems.
All government buildings, Federal, State, County, City etc. should be mandated to be energy efficient and must use renewable energy on all new structures and structures that are been remodeled/upgraded.
"The goverment should serve as an example to its citizens"
Jay Draiman

Northridge, CA 91325
Email: renewableenergy2@msn.com

High winds caused another utility company power outage early Saturday morning. I was sleeping and didn't notice it at first, but then it got very cold in the house. I switched my stove (corn-burning fireplace insert) to battery power and connected bathroom lights so the kids could get ready for church.

My small PV system has come to the rescue on several occasions in the past year. Power from the system kept us warm, kept water pipes from freezing and bursting, kept food from spoiling, and provided electricity for lights, communications, and entertainment. Recently, some of my neighbors had to move out of their homes when a severe ice storm caused a power outage that lasted more than a week. The cost of dealing with that outage alone for the average family could almost have paid for a PV system like the one I have.

The economics of solar PV extend far beyond comparing the cost of the system with the cost of power from the utility company. My system is small, and growing, but it already meets our basic needs. With each upgrade we gain additional functionality.

On the other hand, if your utility power never fails, and you expect the rates remain reasonable, there is no need to consider an alternative system. Perhaps you live in a warmer climate, and are not concerned with a loss of power for heat. If you want to continue to purchase electricity, most of which is produced by coal-fired power plants that poison water sources and spews out carbon monoxide, that's your choice. I chose to prepare for emergencies and to be as kind to the environment as I can. I try to help others do the same by writing about my experiences on my blog:



One thing I didn't put in the spreadsheet was consideration of off-grid power. The problem with off-grid systems is it's hard to do good energy storage. So often you will get a system where the batteries are well charged and the energy produced by the panels is discarded. You can't keep the batteries in deep discharge all the time, it's not good for them. Newer battery technologies may help that.

But anyway, with an off-grid you must then add a factor describing how much of the energy you will actually get to use. If you throw away a lot, it's harder and harder to make your system economical. For the off-grid person, "economical" may mean compared to generators or other forms of power, rather than compared to the grid. Generators, polluting as they are, only are on when you truly need power, and combined with batteries you will use all their power. (Generators without batteries can also be wasteful if you run them with less load than their idle power production.)
Grid-tie is just so much better at this, which is one reason a lot of the rebates and credits only apply to grid-tie. (The other is demand side management.)

A good design is probably just enough solar so you will always use all of it, some batteries to store rare excess and a smaller generator for high demand or when the batteries get too low. Plus some wind if practical and hydro if available. Or of course, solar, wind or hydro with grid tie. Batteries with grid-tie may be a good idea if you want just a little backup during grid outages, though a generator may make more sense since for most people, grid outages are quite rare, so the pollution question is minor.

Some people think they are green because they take a solar panel on camping trips. That's not green at all, since the panel consumed a year or more of its own output to be manufactured. (Used to be as much as 4 years.) Unless you camp all the time, you're just storing energy and not being particularly green.


Thanks for the blog. Actually stumbled upon it looking for HDTV info, and fell into your solar discussion. Seeing as I've been into it for a few decades. You seem to have a good handle on the topic. However, there are a few aspects to economics, especially in California that could use some solar light. Many investor owned utilities in California have a tiered electrical tariff. It is not a straight $0.08/kWh, it is minimal $0.12/kWh up to $0.40/kWh depending upon monthly usage. The more you use, the more you have to pay. So you can see that California incentives for solar, combined with the high costs for consumers that use lots of monthly electricity, provides for better economics. There is a calculator available for free that combines all the utility rates, solar radiation, and monthly usage inputs. Best thing about it, all you really need to know initially is your zip code:


Thanks again for the blog. If you want to know how we are going to be reducing installed PV system costs, ask me about thin film PV. Hope this helps.


PS: I like the way you think, and that is really scary ~smiley~

I see one key factor I was missing. Home owners can get home equity loans to pay for the panels, and those are tax deductible. (I've been building a new business of late which has alas put me in the start-up red for a while so that's not as useful for me, temporarily.)

Due to California's tiers, the right approach is to put in just enough capacity to get your use down to the baseline, and buy grid power for that. Thanks to the taxpayer, the solar system can indeed compete with the crazy above-baseline California rates.

If instead a corporation owns the panels, they get the full federal tax credit, and of course all their costs are tax deductible. However, your own payments to them would not be. This is a downside of something like CitizenRe, if not for their incredibly cheap panels.

Annoyingly, that page you link to does not appear to work under firefox on linux.

Doh, sorry about that IE requirement. The developer is kinda stuck on MS. Don't shoot the messenger. If you get the chance, maybe at a library or something, try it in IE. Some cool graphics.

Best Regards,


“Can the energy crises be overcome?” – I say yes!

I think that the public, the government and corporate America should treat these energy crises as a danger to our way of life.

During World War II, the America we know unified in a common cause. Everyone rolled their sleeves to chip in and Americans produced an enormous amount of hardware for the war effort. “I see a solution within 36 months”.

If we as a nation can really appreciate and understand the severity and enormity of the energy crises, the catastrophic impact on our economic stability and civilization,
we must unite and do whatever is necessary to produce other forms of energy and overcome this energy and economic crises “by putting all politics and egos aside and look for the good of our nation”.

Jay Draiman, Northridge, CA

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