Need a solar system to fully power my home

I am finding it very difficult to keep up with the rapid increase in fuel cost which is driving up my electricity bill. I really need a solar system that can fully power my home but I don't know how to start or what to buy. Please advise me on how to approach this issue and what items to purchase to achieve my goal. I anxious await your response.

Comments

  • BB.BB. Super Moderators, Administrators Posts: 29,717 admin
    Re: Need a solar system to fully power my home

    Maggie,

    My first suggestion is to spend your money on conservation measures first... I don't know where you live, or what type of home you have, how many live with you, what the summer/winter weather is like, etc....

    Basically, a Grid-Tied Solar system installed (the simplest and, usually the best, for 90% of the people out there in the USA), will cost you around $0.25 per kilo-watt-hour to run for 30 years. If you get rebates (like California's ~$3.00 or so per watt rebate), you may drive the costs down to $0.14-$0.17 per kilo-watt-hour. And you have to "pre-pay" (or take out a loan) to purchase the install the solar equipment (my system, call it 300 kWhrs per month, was ~$21,000 cash up front, after rebates). You can do better if you look around (or maybe not, it all depends)...

    Right now, I pay about $0.11 per kWhr (E-1 PG&E, baseline useage under ~300 kWhrs per month). And, my electric power, while pretty high, has not change price for years. So, my $0.14-$0.17 a kWhr from solar is still more than I pay for power today--it is not saving me any money right now---I installed the system to protect against future price increases, and to allow me to charge an Electric Vehicle in near future (power for me, at the higher rates can be $0.30 t0 $0.51 per kWhr if I am over 1,000 kWhrs per month).

    So, you really need to:

    A) Where do you live and is your bill larger or smaller than average? (your power company can tell you this)
    B) What do you use your electricity and gas (oil, etc.) for (AC, hot water, cooking, home heating, etc.)
    C) Do you have appliances over 10 years old (if yes, replacing them can save 1/3 to 1/2 of your bill).
    D) Do yo have 1. Attic insulation, 2. double pane vinyl windows, 3. wall insulation, weather stripping, etc...
    E) What is your power bill (amount of energy used and price per kWhr/Therm/gallon/etc. Per month/winter/summer/etc.
    F) Do you have something to measure your power for each major appliance (fridge, tv, AC, etc.)--suggest a kill-a-watt meter. Cheap (~$34) and pretty simple to use:

    http://www.amazon.com/gp/product/B00009MDBU

    G) Once you have identified your most "costly" energy loads, look at replacing with Energy Star appliances (high efficiency), add missing insulation, and, in some cases, replacing an old AC system with a Ground Sourced Heat Pump (good for places that get very hot or very cold).

    G) If you are thinking about going solar, does your home/property have a good location for several hundred square feet of solar panels with, at least 9am-3pm of good south facing exposure with no trees/homes/etc. blocking (especially in the winter when the sun is low).
    H) Is your first concern Electric or Gas bills? Frequently, using solar hot water heating for a swimming pool, domestic hot water, and/or home space heating, is more cost efficient than going with Solar Electric at first (Solar Electric systems usually have much less maintenance though when compared with solar hot water systems).

    As an example about spending money to save money for conservation... Say you get 5% return on your money in the bank and you have $0.10 per kWhr energy costs. You have a load that uses and average of 100 watts (0.100 kWatts) of electricity an hour (like your fridge), day in and day out.

    Cost per year = 0.100 kW * 24 h/day * 365 d/year * $0.10/kWhr = $87.60 per year.

    Break even expense = $87.60 per year / 5% interest per year = $1,752 spent to save 100 watt load per year...

    Say your old fridge was 200 watts per hour 1,752 kWhrs/year (or 146 kWhrs / month) and a new fridge was only 100 watts per hour (or 876 kWhrs per year), if you spent less than $1,700 for a new refrigerator, you would be saving money...

    I hope that this helps you... Do you have more questions?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 29,717 admin
    Re: Need a solar system to fully power my home

    PS:

    A few other comments. One reason conservation can be so powerful, for example, those using Air Conditioning, is that you save twice, once by not burning the extra energy (the new fridge, changing everything to fluorescent lights or compact fluorescent lights (twisty tubes)) and second, because you are not paying to remove that extra heat through the air conditioner.

    Another reason, if, for example you are using 1,500 kWhrs per month (roughly $500 a month in California), is that you are in the upper tiers of pricing. For example E-1 residential at over ~900 kWhrs per month is almost $0.35 per kiloWattHr. So, eliminating the first 600 kWhrs per month of electricity, saves you $0.35 per hour, or almost 3.5 times the base power rate (you can even spend more money to save money than my example above using $.10/kWhr).

    And, if for some reason you cannot reduce your electrical use below 900 kWhrs per month, you don't need a solar system that can power your entire home. Getting a system that even only generates 500 kWhrs per month is now saving you $0.35 per kWhr, already cheaper than the $0.14 to $0.25 per kWhr it cost you to install in the first place...

    In any case, putting in Solar Electric is not cheap and, for many (if not most) people, won't really save any money at current prices--you are, mostly, just pre-paying your utility bill. For my area (expensive San Francisco Bay Area), before rebates, I would have to spend, very roughly (not including rebates), $72 for every 1 kWhr (or $0.11) I reduced my monthly electric bill ($52 / kWhr after rebates and state tax credits). Your costs will not be the same as mine (I am not very good at getting the cheapest deal), but they are real numbers and can help you understand the basic costs.

    No matter how you slice the problem--using less through conservation is the first way to proceed (me speaking as an engineer--not as a global warming believer). If you want to see to what extremes people go to save energy, go look at Home Power Magazine (6 editions per year):

    http://www.homepower.com/

    You can look at the last edition (download PDF) for free--very nice of them.

    http://www.homepower.com/magazine/download_sample_issue.cfm Download from here...

    Good Luck,

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BrockBrock Solar Expert Posts: 633 ✭✭✭✭
    Re: Need a solar system to fully power my home

    Bill sorry to jusp off topic a bit, but lest say you produce 300kw on peak and use 600kw off peak. Does that put you in the 300kw base or 600kw base?
    3kw solar PV, 8 L16's, xw 5548, Honda eu2000i, iota DLS-54-13, Leaf EV, 4 ton horizontal geothermal, grid tied - Green Bay, WI
  • BB.BB. Super Moderators, Administrators Posts: 29,717 admin
    Re: Need a solar system to fully power my home

    Hi Brook,

    The simple part... I am time of use E-7 (PG&E--California):

    http://www.pge.com/tariffs/pdf/E-7.pdf

    Normally, peak is Noon-6pm, Mon-Friday (no allowances for holiday or not). Rest is off-peak. I do not keep track of what time I am generating, but, roughly, 1/2 is Noon to 6pm, other half is off peak generated (and all weekend is off peak)... Assuming equal sun/power/etc...:

    May ~524 kWhrs (from inverter log). Approximating 14 time periods, 5+4 off peak, 5 peak:

    5/14 * 524kWhr = 187 kWhrs peak (est. solar PV output)
    9/14 off peak * 524kWhrs = 337 kWhrs off-peak (est. solar PV output)

    My May 2006 PG&E Bill showed (this is net power of Power Used (fridge/lights/etc.) - Solar Power Generated): -153 kWhrs (Generated) Peak, -52 kWhrs (Generated) Off-Peak. Total was -205 kWhrs (generated). If you take 524 - 205 = 219 kWhrs used by home (all periods) (this is probably about 30 kWhrs higher than I used to be--I purchased a new freezer that uses about 1kWhr per day).

    Summer rates (baseline--change was May 1) are Peak: $0.29372 and Off-Peak $0.08664 per. kWhr
    Winter Rates (baseline) are Peak: $0.11472 and Off-Peak: $0.08966 per kWhr.

    Regular residential rates are ~$0.114 per kWhr (all year round).

    Baseline is ~300kWhrs (if you have mostly gas appliances). Especially during winter, they will up your base line by a bunch (since I am gas, my gas baseline is what is up'ed for me).

    Now, for the sort of advanced math that is only taught in California (Brock, talk to Darell for the details--he sent me a bit about what was going on)... But, basically, you would think that Baseline is only for energy that you consume... And that Baseline would not be negatively affected if you generate power. In reality, about November of last year, they changed the billing rules (nothing in rate sheet though)... Now, Say you use 300 kWhrs off-peak and generate 300kWhrs on-peak... Well, what they are doing is, saying the 300 kWhrs that you generated is subtracted from your baseline, and now, the next 300 kWhrs for off peak is being billed at the next two higher rates (120% and 200% of baseline which can be over $0.25/kWhr off peak summer)... So, they are, in a way, penalizing you for generating power during peak usage!... Kind of a dumb way to reward people that load shift...

    When I typed about using Solar PV to "shift" my baseline... I was trying to say that, assume that I was paying baseline (300 kWhrs) per month now, and I got an electric car. Now, any of my additional power would have been billed at ~1.7x-2.5x or more just because of the car. With solar, by generating ~300kWhrs per month, those "extra" kWhrs (assuming that I got all of my car power from PG&E) would be around $0.09 per kWhr, instead of around $0.25 per kWhr (assuming off-peak charging)... So, the solar (which cost me ~$0.14 to $0.17 per kWhr generated) is directly cheaper than PG&E power--if I used more power (for charging an electric vehicle or--for running AC, or whatever)...

    Make sense? Or should I have stopped typing 4 paragraphs ago????????

    Take care,
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BrockBrock Solar Expert Posts: 633 ✭✭✭✭
    Re: Need a solar system to fully power my home

    I see, goofey but I get it, thanks.
    3kw solar PV, 8 L16's, xw 5548, Honda eu2000i, iota DLS-54-13, Leaf EV, 4 ton horizontal geothermal, grid tied - Green Bay, WI
  • BB.BB. Super Moderators, Administrators Posts: 29,717 admin
    Re: Need a solar system to fully power my home
    Brock wrote:
    I see, goofey but I get it, thanks.

    Me? or PG&E? :wink: :roll:

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 29,717 admin
    Re: Need a solar system to fully power my home

    Ed,

    I am not at all sure that I understand what you are asking... At first, I thought you were asking about Natural Gas pricing--but if you are doing something yourself, it seems that you may be asking about solar irradiation numbers of 4 kWhrs per day per square meter (not cubic meters)...

    So, I will take a stab that you are asking about solar irradiation numbers. I got my US information from:

    http://rredc.nrel.gov/solar/pubs/redbook/

    You can look up California, and I used San Francisco... Roughly, my numbers are from 3.5 to 6.8 kWhrs per sq. meter (December/July) for Latitude and flat plate collectors...

    However, there are a lot of issues that seem to make these numbers less than ideal to predict your results... For example, in San Francisco, there are areas in the western part of the city that don't see any sun at all during the entire summer (clouds, fog, followed by clouds). Other areas (eastern parts in the older sections of the city) are quite nice.... So, I don't know where they get these numbers.

    Also, the Photo Voltaic Solar Panels are very sensitive to temperature. If you are in a warm climate (not even hot like where you are at) and roof mount them--you can derate their daily output by 75% or more. (also, I had a wet/cloudy winter and generated much less power than predicted by the tables).

    If you can find somebody near you that has a system and they have some monthly figures throughout the year, it will make it much easier to predict what your proposed system will do.

    Not trying to throw a wet blanket on Solar Power--just trying to help set reasonable expectations.

    Is this what you were asking about?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Need a solar system to fully power my home
    However, there are a lot of issues that seem to make these numbers less than ideal to predict your results... For example, in San Francisco, there are areas in the western part of the city that don't see any sun at all during the entire summer (clouds, fog, followed by clouds). Other areas (eastern parts in the older sections of the city) are quite nice.... So, I don't know where they get these numbers.

    Bill,

    Good point about station location and microclimates. Each station identification includes the coordinates for its location. For San Francisco (Lat(N): 37.62, Long(W): 122.38, Elev(m): 5), the station location appears to be SFO International Airport (ref Google Earth).

    HTH,
    Jim / crewzer
  • BB.BB. Super Moderators, Administrators Posts: 29,717 admin
    Re: Need a solar system to fully power my home

    Thanks Jim,

    Duhhhh, I had a blond moment. Yes, the lat/lon location is right on the top of the page in big numbers. Right about at the north tip of one of the runways almost on the shore of the SF Bay.

    SFO is more sunny than much than western San Francisco. However, 7 miles south (where I live) has fewer cloudy periods and is much warmer. And, technically, SFO is not even in San Francisco but 7 miles south of the city.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    San Francisco Monitoring Stations

    BB,

    The San Francisco PUC has 11 monitoring stations in San Francisco. They publish some of their data on line and they'll send you their full data logs if you ask:

    http://sfwater.org/detail.cfm/MSC_ID/64/MTO_ID/139/MC_ID/7/C_ID/1888/holdSe
  • BB.BB. Super Moderators, Administrators Posts: 29,717 admin
    Re: Need a solar system to fully power my home

    Pretty nice site!

    Interesting in that is shows about a 10% difference between the west and east stations. I would have expected a larger difference--but you can't argue with actual measured numbers. Hmmm

    Using their numbers, and a 3kW system (like mine)... They are estimating, roughly between 3,600 and 4,000 kWhr/year... I am about 16 miles southeast of San Francisco (near the shore of SF Bay) and my roof mounted (facing SSE ~155 degrees true) PV system will produce around 4,700-4,800 kWhr in one year (est., my first year anniversary is 9/5/06.

    Are my numbers above, below, or average for my installation? Don't know.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Need a solar system to fully power my home

    Bill,

    These may be old news to you, but here are some links to PV systems running in the San Francisco Bay Area:

    http://www.fatspaniel.com/datapage.html

    http://view2.fatspaniel.net/FST/Portal/SunPower/urban/HostedEndUserView.html

    http://www.siliconvalleypower.com/res/?sub=haman

    http://view2.fatspaniel.net/SSH/MainView.jsp
  • BB.BB. Super Moderators, Administrators Posts: 29,717 admin
    Re: Need a solar system to fully power my home

    Thanks for the links...

    Hmmm... Looking at the Urban School in SF, they are using 37 kW right now (9am on a Wednesday) with, apparently no students for the last few weeks (according to their calendar). Would be nice to see power usage closer to their weekend amounts (which still seem high for an empty set of classrooms).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Need a solar system to fully power my home

    I agree, that's a lot of KW for an idle building.

    Maybe they have other activities during the summer.

    I'm glad that some folks set up on line monitoring sites. We can get a general idea for the range of what's possible here, but there are too many unknowns to do any 'engineering'.

    From what I've seen in this thread, I gather that you're located some where south of San Mateo. Maybe one of those systems in Palo Alto will be a good cross check. I suspect that if you contact them, they'd be happy to email you some more details of their system(s).
  • BB.BB. Super Moderators, Administrators Posts: 29,717 admin
    Re: Need a solar system to fully power my home

    I went to their web site and looked at the calendar for summer--no activities or summer school listed for most of the summer.

    My location, I am right in the middle of the City of San Mateo (a mile south west of the intersections of highway 92 and 101).

    I do have a 3.5 kW grid tied system and it has been turned on since September of '05. It appears, to be relatively on track for generating 4,500-4,800 kWhrs for the year. The installer predicted 5,300kWhr/year. So, the system is performing about 10% or so less than designed (we had a very cloudy/wet winter--would I average more? Don't know--ask again in 10 years). From the design of the panels (and their thermal deratings), the Inverter, orientation on my roof, etc., I think that everything is working just fine. I did not automate any data collection (burning power with a computer for solar data collection seemed to be counter productive to conservation)--I just take the daily readings (kWhrs generated) by hand. I don't really know what I would do with more data.

    What I was really wondering about was more the "average weather" and how we are doing this year vs other years. Although, in a way, it really does not matter too much. The amount of sun that I get today is it... No more and no less. I can't do anything about the weather so I am just along for the ride.

    What I am really trying to do is help people understand that Solar, while nice, is not quite the same as turning on a light switch or opening the gas valve. It is a product of nature (and physics) and therefore don't expect miracles from a solar installation. If it is very cloudy weather for a week, that power is lost forever. If you put in twice as many panels as you need, sometimes you will have way more power than you can shake a stick at. And, at other times, you will still not have enough without some other form of backup--or just going without.

    I chose grid-tie for my home even though I really would have like the battery backup for here (California designed brownouts and earthquakes)--but Grid-Tie was best for me. Batteries cost money, need servicing, a place to put them, and can only store a few days of power. PG&E (via the Cal PUC), basically made PG&E a 1 year unlimited storage battery for my power--all at the costs of less than $6 per month (assuming that I am a zero or net generator of power over 365 days). I also chose Time of Use metering (peak power is noon-6pm Mon-Fri. $0.29 vs $0.09 per kWhr during summer).

    For $900 and a few gas cans, I can ride-out any of the short term emergencies that may come.

    The only way I can make my system any better would be to cut down/back a couple neighbors' trees and rotate my house from ~155 to 180 degrees (due south).

    Overall, you can actually do a lot of engineering predictions, and they usually workout pretty well... But people don't really like the answers (same as in business when marketing and engineering start talking past each other).

    For example, we have one thread about camp cooler and solar--planned on only using a 50 watt panel, but engineering the solution showed that a 230-300 watt panel would be needed (and at $5 a watt or so per panel, that is a big cost adder). Another was the sailboat thread... Wanted to generate all the power with solar panels. Engineering said that it would not really be satisfactory only using the existing panels--suggest looking into alternative energy sources/conservation. And today's race note's comment that 3 days of clouds is forcing electron rationing.

    It is just the nature of the problem and expections. If you set expections correctly, solar is a great solution. If people try and under-design a solution (and, many times, lack of maintenance) to save money (and/or if the result of high-pressure sales tactics)--they will not be happy.

    Another example, around here, a lot of people installed domestic hot water systems.... On the coast where there is fog and trees--people did not get much heat and fog rotted many of the systems. On the sunny side of the hill, many used plastic domes which crazed and darkened in relatively few years. Again, giving solar a black eye. But you could go down to Scotty's Castle in Death Valley and see a properly build (locally designed and maintained around 1930's) solar hot water system that worked well for many years.

    p://www.oldengine.org/members/levans/dv/dv11.html (photo of Scotty's Castle Solar Hot Water installation)
    http://www.oldengine.org/members/levans/dv/ (rest of the shots around Scotty's Castle/Death Valley--Old Iron)

    In the end, I chose I my first major solar project to be solar electric because, 1) I could charge an electric vehicle--I hope--in the near future, and 2) because I wanted something that would last several decades without much maintenance. I was not sure solar hot water (gas was about 1/2 or a little more of my utility bill) would meet that requirement (even though, it should be much cheaper to install solar domestic hot water wrt to utility costs).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Need a solar system to fully power my home

    Sounds like you've done a good job is getting set up for the next big one.

    There are mechanical design issues that matter a lot in Earthquake Country that don't seem to get discussed. It's hard to say how well a PV system is going to do in a major quake but there are things that should be considered -- like using flexible solar panels.

    What I meant about not having enough info to do engineering is that we don't know important stuff like which panel(s) are being used and how the strings are configured. For example, the system at Haman School is rated as 4.9KW DC but it maxes out at 3KW. I've talked to the guy who designed/installed that system. I could never get the details of how it's configured but he just doesn't see this as a problem -- or at least he won't admit that it is a problem.

    If I'd built a system that maxed out at 60%, I'd be trying to fix it.

    I agree with your comments about long term weather data. I don't know if you plugged in the coordinates for the SFO weather station into Google Maps. They're really on the boarder of the fog belt. I suspect that their numbers for late June throuh late August are lower than your site.

    The weather stations in San Francisco are a big step forward. It would be great if we could get something like this set up in other cites. One idea would be to organize something with the schools. They've got real time irradiance data from their systems. This could be a major asset for other people.
  • BB.BB. Super Moderators, Administrators Posts: 29,717 admin
    Re: Need a solar system to fully power my home

    Earthquake wise--I am not too worried about the solar panels. I just changed the roofing shingles and there is 1/2 or 5/8 structural plywood underlayment for the whole roof (new earthquake code requirements when re-roofing). Also, mounted on metal frames.

    If the panels get totaled--I am already in a world of hurt. If you remember, many of the homes in the earthquake were destroyed when either the first floor collapsed (soft story) or from fire.

    And, I just found out that our local utility is changing all of their gas service from iron pipe to somesort of tough plastic line. Plus, they are adding a flowrate shut-off valve (if house pipe is broken, the gas flows at full volume, and the internal valve slams shut until the flow is stopped (and the gas back pressure bleeds off). So, there is a new anti-fire measure coming over the next 10 years for everyone in California with natural gas.

    The big issue with Grid-Tied Solar, is that the inverter will not supply any power if there is no utility power--and I don't think it will work with a generator either (for various reasons). I would like to get an Outback MX60 controller and a few batteries--but the typical Xantrex Grid-Tie runs from 195-600VDC... The MX60 shuts down above 135VDC and fails above 150VDC. Can't just through a cut-over switch into my arrays--I would have to rewire too. Hence, just a generator for now.

    Don't know anything about the Haman school... But if you look at the numbers, right now (10:30am) they are getting 3,898 kW peak... And the panel temp is around 117 degrees F. That is about what I would expect it to produce... [as I am typing this, is is now 4,025 watts output; edit: and now 4,153 watts at 11am--probably pretty close to peak power]

    My 3.5 kW system highest peak I ever saw (not logged, just walking by and looking) was 2.998 kW peak (inverter limits to 3.0 kW peak). And, typically is around 2.5 to 2.7 kW on a nice summer or spring day... The cooler the weather, the higher the power supplied for equal sun. So, for the Haman School, I would have expected nominal power to be (including inverter eff of 94% for my system):

    4.9kW *2.5kW/3.5kW= 3.5 kW typical peak in hot weather... And 4.2kW peak on cooler days...

    Temperature is a big deal for these solar panels. And the STC ratings are quite a bit higher than you would expect in any nice weather above 70F.

    Jim (Crewzer) did this and found that the SF site was right at the north tip of one of the main runways at SFO airport. Yes, sunnier than some parts of SF, less sunny (buy much cooler) than San Mateo.

    To see what temperature different panel configurations do to actual outputs, Xantrex has a nice support site for their Grid Tie inverter family:

    http://www.xantrex.com/support/gtsizing/index.asp?lang=eng

    You can see there is STC (panel manufacturer ratings), PTC (numbers use by California PUC for rebate base numbers) and CEC (PTC - Inverter Eff and limits). CEC is what CA gives the rebates on.

    Pick Solar Panels "BP 4175", Inverter "GT3.0" and look at 2 strings of 10 panels and you will have my system.

    So, unfortunately, 60-70-75% output is not an indication of poor system design--it is more a function of site, time of day, temperature, weather, and overall efficiencies.

    I always thought it would be neat to sell a 6" solar cell with a small data logger that you could just throw on a roof for a month (or even 1 year) to actually give site specific performance. And sprinkle a few of these around a city or on people's home who are interested in solar. In reality though, simple charts, and estimates are about as accurate and can give you answers with a few minutes or an hour of work.

    In the end, for Solar, it is usually expectations that need to be adjusted, and not the equipment. Cheaper and more efficient panels would be great for everyone--but I would not hold my breath for anything like that in the near future. Demand is just too high right now, it cost lots of money to make a panel that can withstand 30+ years of weather (thermal cycling is a real killer for any sealed element), and there is only so much you can get from Silicon and a little doping.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Need a solar system to fully power my home

    OK, I checked my notes and I see that Haman School peaks at 4.2KW - so I was wrong when I said 3KW in my earlier post.

    Thing is, the guy who designed this system claims that 4.9KW rating includes all derating for site geometry, string configuration, temperature, cable loss, inverter loss,...

    He was very proud about how he rates his systems.

    He's got a short fall of about 15%, based on his sizing calculations. 15% is a lot better than 40% but it's still a lot of power.

    You can get a fairly good idea of average irradiance in San Francisco from the sfwater.org data. If you convert their plots into irradiance by counting pixels you get:

    Jan Feb Mar  Apr  May  Jun  Jul  Aug  Sep  Oct Nov Dec  Location
    59  84  119  149  177  192  181  155  139  98  57  36     Moscone
    58  79  118  150  183  196  183  154  126  96  68  44     North Point
    61  81  117  145  172  177  132  114  126  83  72  49     Washington

    where, 57 pixels == 0.200 KWH/ft2/day

    As you know, Moscone Center and North Point have almost no fog, and Washington High School is deep in the fog zone.

    The data says that the total power over the course of a year is only 8 -- 9 percent higher in the sunny part of the SF relative and the most foggy part of town. That's a lot lower than I had expected before I started looking at the data.  If you want to do this accurately, you can ask them to send you their data logs. I suspect that this SWAG is good to about 2 or 3 percent.

    Given your location, I suspect that the you could use the data from either the Moscone or North Point monitoring station.

    We've lucky here in SF Bay Area, we've got good data sets to work with. The calculations are fairly straight forward. I haven't done a full error analysis but I suspect that the total error should be less than 5 percent.

    I think that there may be a lot more flexing of the PV panels during an earth quake than you might expect. Wood frame buildings are going to be doing a lot of twisting when the S-waves come through. Things attached to the outer surfaces of buildings tend to get splayed off, in much the same way as metal splays off the back of plate that's impacted from the front. It's an energy coupling issue, the same basic thing that causes strong shaking in loose soil (or in the optical world, reflections).

  • System2System2 Posts: 6,290 admin
    Re: Need a solar system to fully power my home

    Hello BB,

    I am in the SF area also and signed up (had to sign up?) for TOU E7. I read you comments earlier "In reality, about November of last year, they changed the billing rules (nothing in rate sheet though)... Now, Say you use 300 kWhrs off-peak and generate 300kWhrs on-peak... Well, what they are doing is, saying the 300 kWhrs that you generated is subtracted from your baseline, and now, the next 300 kWhrs for off peak is being billed at the next two higher rates (120% and 200% of baseline which can be over $0.25/kWhr off peak summer)... So, they are, in a way, penalizing you for generating power during peak usage!... Kind of a dumb way to reward people that load shift..." I don't understand why would I get billed at 120% & 200% - worst case if I use 300 off peak after generating 300 on peak, wouldn't I just get zero credit?

    Tom
  • BB.BB. Super Moderators, Administrators Posts: 29,717 admin
    Re: Need a solar system to fully power my home

    Tom,

    First, good for you that you got the E-7 TOU--that is, IMHO, much better than the E-6 rate that they were forcing on all new solar customers (and will be again in the near future--possibly even for me--and old customer of 1.5 years).

    As Mike has posted in another thread, California is (or will be) changing the rules to allow solar customers to again use E-1 too, at the customer's option. In some areas, disallowing the use of E-1 (and how bad/complex E-6) is for solar customers (especially those that may start with smaller systems to try it out first) there is the real possibility that some people would install solar PV and pay more for electricity (because they use power during Peak Times and the smaller solar systems don't offset all of the peak time use).

    If you can offset power usage to non-peak times (washer/drier/AC/etc.), E-6 does work with solar PV--but it is not as good for the customer as E-7.

    Regarding the use of Baseline Billing and how solar PV affects it--I am just relating some email I got from another person about the issue. It was not completely clear how PG&E did it then--but many folks (especially those with electric vehicles) were finding that Solar Generation (net metering with more power generated during Peak period then used) was being treated, for baseline calculation purposes as if they were consuming power--so it was jacking up their off-peak rates. Last I heard, PG&E did change the way it was being calculated somewhat--but I don't think it was still being done fairly. This was hitting folks hard that had two meters (one E-7 TOU for house power and solar PV connection and another like E-8 or E-9--I think it was those rates--to charge their cars--it turned out eventhough the EV Car rates were very low for middle of the night, the way BaseLine was charged/calculated, it was better for them to get rid of the extra meter).

    For me, my system usage and generation has not caused me any issues (my generation and consumption is not that far from each other wrt peak and off-peak periods)--so I have not had to personally call PG&E for an explanation of what the heck they are doing (then or now).

    My guess for the reason PG&E was aggressively charging for an "unbalanced" use of +300 peak and -300 off-peak was that they are allowing net metering because of state laws--not because it makes money for them (PG&E purchasing power retail and selling it retail is not a way to stay in business for long). Also, in theory, for residential users, most of the cost of our power is in the distribution and transmission line costs (so, the power lines are now used to move power from my home to the neighbor next door--but I am not "paying" PG&E to move the power to my neighbors)--not in the actual production of kWhrs of electricity at the generator plant. Anything that they can do to yank some money back in the transaction--they are going to give it a try.

    In the end PG&E is doing the Solar stuff because laws were passed--not because they are nice guys and believe that this is going to save the world (or even make them money).

    And, per Mike's posts about the state/utilities changing rules and instantly killing the Grid-Tie solar market--they obviously have little knowledge about the "law of unintended consequences":

    http://www.wind-sun.com/smf/index.php?topic=2191.0

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Need a solar system to fully power my home

    Hi BB,

    Yes, I saw the thread about CA giving solar customers a choice now, that is why I'm wondering whether I should really switch to the E7 TOU or try to stay on the E1. I looked at the E6 with the partial peak period as well - do you say the E6 is not as good because of the peak hours being 1-7pm instead of 12-6pm for the E7? I can generally delay my washing/drying to off-peak though there is some electrical usage to cook before 6pm sometimes. I figure I should still be generating more than I can use from 12-5 even if I have to use some of it from 5-6, so it seemed TOU should still be better for me?
    Tom
  • BB.BB. Super Moderators, Administrators Posts: 29,717 admin
    Re: Need a solar system to fully power my home

    You can try this solar calculator--for PG&E it includes most of the available residential rates (E1, E6, E7 and all-electric baseline rates):

    http://www.sunpowercorp.com/homeowners/solar_calculator.html

    Of course, it does not allow you to plug in your own numbers reflecting power usage at differing times of the day... However, for me, it did show that E-7 gave me better rates than E-6 or E1 (in fact, I just tested it now and found that my E-1 billed equaled my E-6 bill--don't know if that is a bug in the program or it just averages out that way).

    The web site used to work fine with FireFox--but the "Click to View..." buttons don't work know--might work with IE--but I don't use IE unless I absolutely have too...

    I like the E-7 Rate because it was simple to explain to wife and kids (noon-6pm week days--don't waste power--especially between May 1st through October 31st when rate triple during peak time). E-6 is weekdays, weekends, peak is weekday only, partial peak is weekday and weekends--differing times, charges, etc... I just did not want to go there.

    You can look here for the current tariffs (electric here, gas just a click away):

    http://www.pge.com/tariffs/ERS.SHTML

    Don't get me wrong, I think that E-6 is much more "fair" to the utilities. Partial and peak times of E-6 track their real load curves. E-7 does not. E-7 is weighted more towards the Solar Customer and when we generate power.

    Just for fun, here is the link to CAISO... The agency that brokers about 75-90% of the power in CA:

    http://www.caiso.com/ (home page)
    http://www.caiso.com/outlook/SystemStatus.html (today's power forecast/usage)

    If you don't use too much power during noon-6pm during the week, E-7 is great. Even if you use the occasional electric toaster oven/microwave to cook dinner at 5pm weekdays--it is not going to hurt you too badly. I assume that you will still generate more power than you consume during these time periods--so any "excess" power you use then will just not be available to offset your off-peak usage (at the cheaper rates).

    My house is gas (stove, central heat, hot water, gas drier)--so my heavy power usage is not that high anyway (I will use electric heater in one or two rooms during the winter--rates are low, and with net metering, I make up for it in the summer).

    In the end, usually, you need to sign up for Net Metering / TOU for a 1 year minimum period. So--you are probably stuck with your rate plan for now.

    Another suggestion would be for you to get a Kill-A-Watt meter (such as from our fine Forum provider Wind-Sun):

    http://store.solar-electric.com/kiacpomome.html

    You will probably be surprised at which appliances are sucking down the most power... For example, my washer/drier only used an average of 5 kWhrs per month or so (and, I quickly figured out that I could save almost 1/2 of their usage by placing on a switch power strip--the 10 watts standby load of the washer/drier electronics 24x7x365 day almost equaled my usage of the washer and occasional drier use--we hang dry other than winter).

    If you have older refrigerator and/or freezers, checking with the Kill-A-Watt meter (running it for a week or so) will quickly tell you if you would save money getting new ones (older fridge/freezers used 2-3 kWhrs per day--or more. The new ones use just a bit over 1kWhr per day).

    Also, found my old stereo was using more power "turned off" than my laptop PC does turned on. So, the stereo, TV's, DVD players, HD Receiver, VCR, various wall warts, laser printers/copiers, washer/drier, etc., are now all on power strips.

    It sounds silly to switch off unused electronics... But when you do a little math. You see how badly a few tens of watts on 24 hours per day really hits you... For example... My lowest monthly usage was about 175 kWhrs.

    175 kWhrs / (30 days per month * 24 hours per day) = 0.243 kWatts or 243 watts average 24 hours per day.

    Just switching off the Stereo and Washer/Drier when not used saved about 30 watts*24*7*365-- or saved me about 12% on my bill monthly power bill. And if you are on E-7 TOU, during the summer, that little 30 watt load is now charged at $0.29 (or more) per kWhr whereas off-peak is only $0.087 per kWhr.

    Or, that 30 watt standby load (during summer, and peak pricing noon-6pm weekdays) is equal to (30 watts * $0.29/$0.087 =) a 100 watt load during off-peak times.

    Also, I have found that reducing power (CFLs, appliances, etc.) has kept our home quite a bit cooler in the summer--so far we have been able to avoid A/C and its costs. I use ceiling fans and I have installed wall insulation, double pane vinyl windows, and an operating skylight to help reduce heat loss/gain. Been really happy so far. Now if I can just get my two daughters to reduce their shower usage.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: Need a solar system to fully power my home

    Bill,

    Thanks for the pointer to the Sunpower calculator. I ran my setup through it and it pretty much makes sense, except for why the amount of energy I would buy from PGE varies depending on whether I select E1 or E7 - it actually says I would buy more energy from PGE with E7 almost every month (maybe it assumes I'd defer my usage until after the peak and then I would have to buy it at night). Anyway, it's good enough for a rough estimate and says I would save some with the E7 over E1.

    Just bought the Kill A Watt meter. I think I have several electronics pieces that use standby power. It'll be interesting to see just how much.

    Tom
  • mike95490mike95490 Solar Expert Posts: 8,470 ✭✭✭✭✭
    Re: Need a solar system to fully power my home
    none wrote:
    OK, I checked my notes and I see that Haman School peaks at 4.2KW - so I was wrong when I said 3KW in my earlier post.

    Here's the link to the Haman School: http://www.siliconvalleypower.com/res/?sub=haman
    or at least it's the link I found
    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 ,

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