Will a pv system save me $ on utility bills or not

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Hello everyone ,

I'd like to raise a question about something that seems confusing. we've got many types of RE devices that we discuss on this forum, and how cost effective/efficient they are. but something confuses me.
I've just seen a post by "Icarus" (or Tony) saying "if you're planning on installing a re device to save $ , you're dreaming" check post #3 here:http://forum.solar-electric.com/showthread.php?t=4926and we've got other members saying similar.
.

so, while installing pv for environmental reasons is a nice ideology, right now there are other things on my mind, and I cant install such a system unless it will one day free me of an electric bill.
So, whats the deal? will today's RE systems save $ or not?
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Comments

  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
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    Re: Will a pv system save me $ on utility bills or not
    so whats the deal? will today's re systems save $ or not?

    Wow. This should light some fires.

    The answers is... it depends. It depends on your location, usage, the type of system that you implement (off grid or grid tie) and, if GT, the rebates/incentives available to you at your location. The cost of implementation can be quite high. Often tens to hundreds of thousands of dollars, making the return on investment period quite long. Depending on your age, you may not live long enough to realize it.

    Conservation is the best way to save money on energy use.

    Edit: I checked the Icarus post. I think what Tony was trying to get at was that we get an awfully big bang for our buck from the electric utility. Even though he doesn't use one. ;) It reminded me of the 50' & 60's when our power company, Northern States Power, ran TV ads (one has to wonder why) featuring Reddy Kilowatt and a catchy little jingle... "Electricity is penny cheap from NSP to you!"

    reddysmall.jpgMaking your own electricity is expensive.

    K
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
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    Re: Will a pv system save me $ on utility bills or not

    I installed a 4.5KW system some time ago. Cost about $45K I point to it, and say,
    I bought that instead of a new car. (no auto union jokes please).

    My electric bill dropped from about $1,440 yr to $150 yr (monthly connection fees)
    I figure if rates stay the same, the payback is about 30 years. If rates go up, payback is shorter, and then I put the $ in my pocket.
    My cost KWH was about 0.17 if I recall.

    If your rates are lower, your payback will be longer.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • john p
    john p Solar Expert Posts: 814 ✭✭✭
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    Re: Will a pv system save me $ on utility bills or not

    Mike 90045 If you had put that $45,000 in an term investment account and even if you only got 4% you would have received $1800 your electricity acc was $$1440.. And you still paying $150 conection fees..a little be left over to put aside for future increases in electricity.. at end of 30 yrs you still have the $45.000 to either reinvest .. but your solar system after 30 years be how much in need of replacement??:D
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
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    Re: Will a pv system save me $ on utility bills or not

    I'm betting rates go up. soon, quickly, painfully, ala Peak Oil. One worry out of the way. Food is another matter. A PEV will still run me around town.

    If you are in TVA area, and electric is 0.04 KWH, it'll never pay.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: Will a pv system save me $ on utility bills or not

    you actually can eliminate your electric bill, but it costs quite a bit up front.
    as to why some people do this (at least for offgridders) you can read some of that for yourself. many of the same reasons may apply to those on grid tie too.
    http://forum.solar-electric.com/showthread.php?t=4368&page=7
  • TnAndy
    TnAndy Solar Expert Posts: 249 ✭✭
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    Re: Will a pv system save me $ on utility bills or not
    mike90045 wrote: »
    I'm betting rates go up. soon, quickly, painfully, ala Peak Oil. One worry out of the way. Food is another matter. A PEV will still run me around town.

    If you are in TVA area, and electric is 0.04 KWH, it'll never pay.


    I'm in the TVA area and it AIN'T 0.04kwhr, believe me.

    TVA's wholesale rate is 7 cents, and by the time it gets thru the local retailer, it's 9 cents at my meter.....down slightly from a fuel adjusted cost last fall of 9.5 cents.

    But TVA also has one of the better infeed tariffs going.....they pay 12 cents kwhr OVER whatever the local retailer rate is for all solar power produced.....currently that would be 21 cents,

    Say I use 900 kwhrs/month ........energy charge is $81 + $8 flat customer charger = $89 power bill.

    Say I produce 350 kwhrs ( about what my system averages ) in that same month:
    350 x .21 = $73.5

    Net bill: 89 - 73.5 = $15.50

    To the original poster:

    Cost of my system: About 20,000 bucks. Payback time ? 15 years at current rates.....and AFTER you factor in the tax credits.

    But guess what...I don't care. and no, it isn't a tree hugging love of the environment that causes me to not care...it's the "insurance" factor.

    In my mind, the bubble gum and bailing wire excuse for a grid in the country has so many points it could fail, and throw in the interesting economic times, potential terrorism, and so on, and I can see a real possibility that dependable grid power could be no more. And my 3kw system will run refrigeration, a few handy items like a washing machine, and some lighting......and that's the difference between living the 20th century life, and all those previous centuries......
  • BB.
    BB. Super Moderators, Administrators Posts: 33,476 admin
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    Re: Will a pv system save me $ on utility bills or not

    I in TnAndy's camp too...

    I bought my GT system almost 4 years ago for insurance... Back in 2000, California had "deregulation" (was not deregulation at all, it was a different regulation that forced our Utilities to sell off their generation capacity and become distributors of electricity instead) that was set in law by government and was taking years to update... So, we really have "regulation by stupidity" that allowed others to game the "system" while government sat on its hands pointing fingers and taking both of our major utilities to the edge of bankruptcy.

    We ended up with Enron -- as everyone recalls, but nobody remembers that Los Angeles Water and Power (a government agency) was also in the midst of raking in huge profits selling their power to the grid too.

    At this point, after California's rebates, fed credits, and "1 year Net Metering" with TOU--I have pretty much set my power bill to $5.50 per month for the foreseeable future. But, we had also worked hard to insulate and weather proof our home, use energy star appliances, adding skylights for daytime lighting/ventilation, CFL's (twisty florescent lamps), and just turning things off we don't need. Gets us down to around 225 kWhrs per month.

    I did not do "Hybrid" (Grid Tied + Off Grid emergency backup power)... It the Xantrex XW system was available then--It would have been a real close call. But--realistically, a fuel efficient, small, backup generator will cover my emergency power very nicely (for anything that last over a day). And we have few power outages anyway.

    We are getting "Smart Power" here--today it is optional, but those of us on solar it will be mandatory (according to the PUC rate sheets). Roughly 15 afternoons summer at $0.60 per kWhr--$0.75 for commercial customers)... That was the "insurance" of what I speak. Unknown government actions in the future scare me more than "pure" market uncertainty.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
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    Re: Will a pv system save me $ on utility bills or not

    Ok, since I am named in the OP, I will chime in.

    As with many things, "it depends on how you define "save money""!

    Any payoff, irrespective of rebates/tax credits etc is long term. The reality is that a much "smarter" series of investments (both to save energy and also save money) would be, in some relative order; Conservation, followed by a bit more conservation, followed by yet more conservation! In short, investing $X in Pv to power an inefficient load (house/business/farm/cottage etc) makes little or no sense. Even though the price of Pv has come down significantly in the last year or so, (how much due to reccesion, how much to more availability of hardware is subject to debate).

    Some examples of conservation are obvious, such as adding building envelope insulation, really a no-brainer as the pay off in net energy/$$ savings are very quickly paid off. Other examples are less obvious, but no less effective. For example, changing out a conventional A/C system for one that uses it's waste heat to heat DHW, or a pools. Or a ground water/earth source heat pump.

    Solar hot water is much cheaper and therefore provides a much quicker payback.

    The bottom line, is the reasons to invest in Pv run the gamut from saving the planet to "sticking it to the man" to it's the only quiet power I can get. I fall into all three camps sort of.

    The other answer is, it really depends on what your grid power costs. If you get BPA/TVA subsidized power at ~$.10 kwh and you live on the drizzly NW coast it makes a "payoff" pretty hard. On the other hand if you live in AZ or CA (or other places) with time of day metering with expensive KWH costs at peak afternoon hours, time of day billing such that you can sell power at the high rate and then buy it back at the cheaper rate, the payoff (coupled with rebates/tax credits etc) can be quite quick.

    So my answer in short is,, it depends on how you define save me money.
    My little system cost me maybe $1500, and provides virtually all our electricity needs. Add in some propane for hot water and cooking and the fridges and our total household energy bill is pretty small. On the other hand, $1500 would buy, at current prices about 1500 litres of gasoline for the Eu 1000. 1500 litres of gas would run that genny for ~6000 hours, at 4 hours/day would be ~4.1 years. (Probably need a new Eu 1000 by then!)

    Tony
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
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    Re: Will a pv system save me $ on utility bills or not
    john p wrote: »
    Mike 90045 If you had put that $45,000 in an term investment account and even if you only got 4% you would have received $1800 your electricity acc was $$1440.. And you still paying $150 conection fees..a little be left over to put aside for future increases in electricity.. at end of 30 yrs you still have the $45.000 to either reinvest .. but your solar system after 30 years be how much in need of replacement??:D

    This is based on the assumption that interest rates will remain stable. I think this is a faulty assumption.

    I remember when CDs paid 9-10%, now if you can get 5% you are very lucky.
    I remember when savings accounts paid 0.425%, now Bank of America pays 0.1%.

    And let's not even get into the stock market.


    Thus, IMHO, comparing investment in "RE for the home" to investment in financial instruments is definitely apples to oranges.
  • john p
    john p Solar Expert Posts: 814 ✭✭✭
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    Re: Will a pv system save me $ on utility bills or not

    No one said interest rates will remain constant. Idont believe its a case of comparing aples to oranges at all.. that arguement could be used the same way on investing in the house.. Look at the number of housing forclosures that are still happening As you would know better than I that in many places almost whole estates are in forclosure with "for sale" signs over them so if you have a house in such an area whats its worth now???so spending another $45.000 would not make the house worth one cent more.
    If you are going to think all other investments are doom and gloom except houses . That to me is not wise thinking..I betcha Jimmy Bufffet will still be investing in other things.
    It is reasonable to think of how if you have $45,000 what other ways it could be used (invested) to reduce an ongoing cost of something.:cool:

    And it still leaves this ..but your solar system after 30 years be how much in need of replacement?? hmmm
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
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    Re: Will a pv system save me $ on utility bills or not
    john p wrote: »
    If you are going to think all other investments are doom and gloom except houses . That to me is not wise thinking..I betcha Jimmy Bufffet will still be investing in other things.
    It is reasonable to think of how if you have $45,000 what other ways it could be used (invested) to reduce an ongoing cost of something.:cool:

    I never mentioned houses.

    In fact, I personally have *never* believed houses are a good investment - unless you rent them out so that the tenant gets to pay the unholy interest load.

    My take on interest is simple; If you can use the borrowed capital to make a profit greater than the interest on the loan, then it's good. If not, then it's bad.

    I've owned a duplex and a four-plex...but I've never owned a single-family residence.

    Sure, there are LOTS of other investments. Renewable Energy on a house however is not generally an *asset* - what it actually is, is a reduction in *liability*. These are totally different sections on the balance sheet. Apples to oranges.

    http://en.wikipedia.org/wiki/Balance_sheet

    For that matter, the house itself is not an asset either - it is a liability. Equity in the property is also not an asset - unless you sell the property and convert the equity into cash.


    Jimmy Buffet is a singer and pilot.
    Warren Buffet is an investor.
  • GreenerPower
    GreenerPower Solar Expert Posts: 264 ✭✭✭✭✭✭
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    Re: Will a pv system save me $ on utility bills or not

    Here is how I made my basis for comaprison.
    A = $ per watt you pay for PV installed, less rebates ...
    B = Average sun hours at your location
    C = PV life time (where your PV system needs to be replaced)

    Your cost per KWhr would be : A*1000 / (B*365 * C)

    Say A=$5 , B = 4 hrs, C= 20yrs , this turns out to be $0.17 / KWhr for the next 20 yrs. Compare this with your local electricity rate factored in your guess for the next 20 years.

    As a reference point, gas generator with 3$/gallon at 20% conversion efficiency (heat to electricity) would cost $0.47 / KWhr . An NG generator at $1/CCF would cost $0.17 / KWhr (assuming the generator cost is insignificant compared to the fuel cost during its lifetime).

    GP
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
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    Re: Will a pv system save me $ on utility bills or not

    Jimmy Buffet invests in Corral Reefer!

    JohnP, do you just like to argue just for the sake of argument?

    Icarus
  • boB
    boB Solar Expert Posts: 1,030 ✭✭✭✭
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    Re: Will a pv system save me $ on utility bills or not

    Gee, I wonder if this $250,000 motorhome and the 3 MPG it takes to run it will offset the savings in hotel bills for the 2 weeks out of the year I use it ?

    boB
  • john p
    john p Solar Expert Posts: 814 ✭✭✭
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    Re: Will a pv system save me $ on utility bills or not

    Jimmy Buffet is a singer and pilot.
    Warren Buffet is an investor.
    Now I know why I couldnt find any Warren Buffet cds at my local CD music store..:grr
  • WisJim
    WisJim Solar Expert Posts: 59 ✭✭✭
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    Re: Will a pv system save me $ on utility bills or not

    We put in our first wind generator in 1977, replaced it with our current machine in 1979, and got our first PVs (at about $12/watt or more) around 1982. Our original incentive was to avoid connecting to a utility that had a nuclear reactor in the area. Our second incentive was to avoid the exorbitant connect fee and minimum monthly fee that the electric utility would have charged us to connect to them.

    We have since moved to a grid connected existing home elsewhere in the state, and moved our wind and solar system with us. I expect the PVs to last for decades after they "pay for themselves", although they paid for themselves in one sense as soon as we hooked them up, due to avoided costs of dealing with the original utility. (Our original system cost was less than the utility connection cost.) (for C = PV life time (where your PV system needs to be replaced), I would use a number closer to 50 for the PV panel lifetime).


    Environmental reasons are important, too. I think that renewable energy is one way to avoid increasing global warming, and that there are other environmentally related reasons to support solar energy, too. I also enjoy working on mechanical and electrical stuff, and to have a "different" kind of lifestyle. People have a good idea how I feel about renewables, and that I have felt that way for decades, and don't mind saying so.

    Payback? My question in return is often "what's the payback on your car, SUV, plasma TV, skidoo, etc?"

    Jim
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
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    Re: Will a pv system save me $ on utility bills or not
    WisJim wrote: »
    I think that renewable energy is one way to avoid increasing global warming,
    Jim

    Ultimately, it's not. Heat is heat, and watts are watts. The more we generate and use, the more heat we make.

    Reducing the greenhouse effect is an important step, but over time, as the population continues to grow, and electric consumption continues to rise (and small scale distributed generation enables even more generation and consumption), heat will continue to be a global problem.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
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    Re: Will a pv system save me $ on utility bills or not
    dwh wrote: »
    Ultimately, it's not. Heat is heat, and watts are watts. The more we generate and use, the more heat we make.

    Reducing the greenhouse effect is an important step, but over time, as the population continues to grow, and electric consumption continues to rise (and small scale distributed generation enables even more generation and consumption), heat will continue to be a global problem.

    I think you are wrong, about this. Heat is not heat. Burning fossil fuel to create heat int he short term ADDS to the heat load of the planet. How much I don't know. Solar power, either DWH or Pv takes solar heat and redistributes it. The heat from my solar water collector is transfered to the water instead of the roof, and then to my shower, then off into the drain. No heat loss, no heat gain. Pv is the same, it takes solar energy,and converts it to electricity, transfers it to an appliance, like a toaster, and gives back the heat. Once again, no gain, no loss.

    Now if I do all those things with oil or wood or propane, I would be adding to the heat load, as well as adding CO2.

    Tony
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: Will a pv system save me $ on utility bills or not

    Good ol' energy entropy!
    Power that arrives on Earth largely as visible light gets turned into other forms of energy, always with some loss in the process. Eventually all forms fall to heat, which isn't bad so long as the amount released into the atmosphere each day doesn't exceed the amount radiated off into space at night.

    There's your problem.

    Burn fossil fuels and you release stored sunlight from 65 million years ago, converting it to heat energy. Add to that the resultant production of 'greenhouse' gases which permit visible light through but block the escape of infrared (heat) and the problem is compounded.

    That's the theory, anyway.

    How much sunlight would be converted to heat each day without human assistance is debatable.

    There is strong evidence that the effects of 'global warming' (more accurately called 'climate change') can only be slowed down, not stopped or reversed. Conservation and the reduction of greenhouse gas production is the best we can do.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: Will a pv system save me $ on utility bills or not
    dwh wrote: »
    Ultimately, it's not. Heat is heat, and watts are watts. The more we generate and use, the more heat we make.

    Reducing the greenhouse effect is an important step, but over time, as the population continues to grow, and electric consumption continues to rise (and small scale distributed generation enables even more generation and consumption), heat will continue to be a global problem.

    now that's a concept few have considered by blaming the sun for global warming. tis true it warms the earth, but to my knowledge isn't responsible for the excesses we are seeing today. well, at least as was pointed out, not directly as it is stored solar energy from fossil fuels in combo with its waste product of co2 preventing the escape of this excessive heat. some don't believe it or care to for other selfish reasons that we are tilting things to a warmer direction.
    one can't blame the use of pvs or heat panels for increasing the earth's temps as this was heat that hit the earth realtime anyway and is just redistributed. our utilizing it is actually saving the generation of excessive heat by burning the stored solar energy in fossil fuels. let's face it, we have burned around half of the earth's fossil fuels in the last several hundred years and it took millions upon millions of years of stored solar energy to create it. adding 1 degree of heat to another degree of heat is as simple as how many tend to add $1 to $1. the math doesn't change, but the attitude seems to.
  • boB
    boB Solar Expert Posts: 1,030 ✭✭✭✭
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    Re: Will a pv system save me $ on utility bills or not

    Hopefully, a lot of conversion processes will become more efficient. Like motor cars... Now there's a good example of waste heat. Make that more efficient and your energy will be converted to real work done, getting you from A to B, rather than some resulting in some work and a lot of heat.

    Of course, in the winter time, up here in the northwest, I need that waste heat.

    boB
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
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    Re: Will a pv system save me $ on utility bills or not
    niel wrote: »
    ok, the article agrees with what i had said in that solar pv does not add to the problem.

    I think I disagree with that point actually. I think that gathering solar radiation in the form of heat (i.e., solar water heating or using concentrated solar heat to generate electricity with boilers or Stirling engines or whatever) doesn't add to the problem.

    But gathering *light* and converting it to electricity, and then converting that to work - with the associated heat - does add to the problem.
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
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    Re: Will a pv system save me $ on utility bills or not

    "What this means for humans is that this is the ultimate limit to growth," said Dennis Bushnell, the chief scientist at NASA's Langley Research Center, who urged Chaisson to publish his idea. "As we produce more kilowatts, we have to produce more waste heat."


    http://www.boston.com/bostonglobe/ideas/articles/2009/01/25/the_other_global_warming/
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
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    Re: Will a pv system save me $ on utility bills or not

    Ruh roh!

    How did my reply to neil's post end up *ahead* of neil's post?


    EDIT: HOLY CRAP! This one did it too... neil's post keeps getting bumped to the bottom of the list. Is this some fiendish new form of "last-wordism"?

    that is weird for i didn't do it and i know bb didn't do it.:-) i put my reply in here just in case something else weird happens.:confused:
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: Will a pv system save me $ on utility bills or not

    ok, the article agrees with what i had said in that solar pv does not add to the problem. i think i disagree on them saying geothermal adds new heat as this heat is radiating from the earth at all times anyway and isn't new heat. much of it is solar heat that the earth absorbed near the top of the crust and a small amount is from the deeper regions of the earth that are hot and are slowly cooling. neither of these are new heats.
  • GreenerPower
    GreenerPower Solar Expert Posts: 264 ✭✭✭✭✭✭
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    Re: Will a pv system save me $ on utility bills or not

    We and scientists just don't have enough data to determine. There are theories on both sides, we hear more on the global warming since these gets more attention by medias. There are news like these:
    http://www.lunarplanner.com/SolarCycles-climate.html
    http://www.dailygalaxy.com/my_weblog/2009/03/scientists-at-m.html

    The process of producing solar panels also produces CO2 at the plants. The process of creating hydrogen for fuelcells et al for electric cars aso produces CO2 at the plants. It's just a different distribution - concentrated at some plants or distributed among consumer appliances/devices.

    I'm for living in harmony with the environment and keep waste down. Human is not the only living being on this planet. Nature has its own way to re-balance things via volcanoes, earthquakes, hurricanes, typhoons ...
    GP
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: Will a pv system save me $ on utility bills or not

    i don't think we should dip too far into this as it is complex and controversial and is too far removed from the op. i did not intend to hijack the thread.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
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    Re: Will a pv system save me $ on utility bills or not

    DHW,

    I'm sorry, but I think you are just plain wrong on this. Light striking any surface, causes light to turn to into (some) heat. A mirror reflects a greater percentage than say a black painted piece of steel, but that reflected light eventually lands on something so that with the exception of some that is reflected back to space, it is all absorbed as heat. Pv solar just moves heat from one place to another. There is, for all practical purposes, no EXTRA heat gained from solar, unlike burning fossil fuel.

    Tony

    From your own link: "The only way to stop this wasted heat from warming our atmosphere is to avoid generating it in the first place, which means using the energy that naturally comes to the planet. When a wind or wave turbine spins, or a solar panel collects rays, they're using energy that's already part of the system."
  • System2
    System2 Posts: 6,290 admin
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    Re: Will a pv system save me $ on utility bills or not
    Here is how I made my basis for comaprison.
    A = $ per watt you pay for PV installed, less rebates ...
    B = Average sun hours at your location
    C = PV life time (where your PV system needs to be replaced)

    Your cost per KWhr would be : A*1000 / (B*365 * C)

    Say A=$5 , B = 4 hrs, C= 20yrs , this turns out to be $0.17 / KWhr for the next 20 yrs. Compare this with your local electricity rate factored in your guess for the next 20 years.

    As a reference point, gas generator with 3$/gallon at 20% conversion efficiency (heat to electricity) would cost $0.47 / KWhr . An NG generator at $1/CCF would cost $0.17 / KWhr (assuming the generator cost is insignificant compared to the fuel cost during its lifetime).

    GP
    Hello everyone, and thanks for all those replies.
    I live in northern New Jersey and electricity is .20 cents/kilowatt hour. actually .202 to be exact.
    figuring out how cost efficient a pv system would be was a little more difficult: I tried using this really cute program here called "in my backyard" http://www.nrel.gov/eis/imby/
    simple to use, just hit the link, click on "imby", and just put in your address draw the pv system on the roof, and it will tell you the size of the system you've drawn, along with payback time for the system you've drawn too.
    but it told me a 4.1 kw system would take 29 years to payback. something doesn't seem right. or maybe it's the trees near my house that would kill pv electric production and the program is picking up on those trees that are south of my house.

    I'd be curious if anyone who HAS a pv system can tell if this program is accurate by comparing it's calculations with "real world" calculations.

    the program does not ask for $/local kw hour. perhaps it already has that info somehow.
  • GreenerPower
    GreenerPower Solar Expert Posts: 264 ✭✭✭✭✭✭
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    Re: Will a pv system save me $ on utility bills or not
    ... figuring out how cost efficient a pv system would be was a little more difficult: I tried using this really cute program here called "in my backyard" http://www.nrel.gov/eis/imby/
    simple to use, just hit the link, click on "imby", and just put in your address draw the pv system on the roof, and it will tell you the size of the system you've drawn, along with payback time for the system you've drawn too.
    but it told me a 4.1 kw system would take 29 years to payback. something doesn't seem right. or maybe it's the trees near my house that would kill pv electric production and the program is picking up on those trees that are south of my house.

    I'd be curious if anyone who HAS a pv system can tell if this program is accurate by comparing it's calculations with "real world" calculations.

    the program does not ask for $/local kw hour. perhaps it already has that info somehow.
    The program is based on PVWatts to calculate the KWhrs produced by the PVs at your location based on the insolation records in the past. So, this is fairly "real-world". You have to play with the "cost" so that the final "$/Watt" would reflect your costs. And the payback is based on 11 c / KWhr electricity cost. Too bad, you can not change that. You can "adjust" the result by 29yrs * 11 c / 20 c = 16 yrs (assuming yours elect. rate is 20 c /KWhr)
    I live in northern New Jersey and electricity is .20 cents/kilowatt hour. actually .202 to be exact.
    Do you really mean 0.2 cents i.e. less than a penny ? Or you mean $0.20 i.e. 20 cents / KWhr.
    At 0.2 cents / KWhr, I don't think PV can beat this. In my formular, it should be adjusted to: A*1000/ (B*265*C*F) where F is the "derating factor" since the STC watts are not "real-world", plus the efficiency of the inverter (say 0.93), the final F is probably around 0.7 to 0.8 .
    GP