How much to go OFF GRID?

GlovesGloves Solar Expert Posts: 65 ✭✭✭✭
Without changing my power consumption habits, what kind of a solar set up would
I be looking at?

Here's my PG&E power usage:
monthlyKWusage.gif

Comments

  • blackswan555blackswan555 Solar Expert Posts: 246 ✭✭
    Re: How much to go OFF GRID?
    Off-Grid means you’ll still have a power source when the utility energy goes down. (Grid tied has to turn itself off due to safety issues)

    Your statement above taken form your website is not correct,

    "OFF GRID" is what it says, Off the grid, eg not connected to the grid/utility service at all, It usually consists of Solar panels, & Charge controller, Wind gen & charge controller (either or both) Inverter/chargers, large bank of batteries( A rough estimation if you were to require what you say, 15kwh per day, 3 days autonomy= 45kwh, use a DOD of 50% = 90 kwh, @ 12v = 7500 ah battery bank) & backup generator,

    GRID TIED, Is also what it says, Tied to grid, eg connected to grid / utility, You can have battery backup for power outages if you want, If you can generate enough, you can also sell back to grid ( with or without battery back-up)

    Have a good one
    Tim
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: How much to go OFF GRID?

    i would think that would depend on what you intend to do for you could,
    1> lessen the bill with some solar.
    2> try to break even so that you don't owe and they don't owe you either.
    3> try to generate an excess for credits toward another billing month or year.

    edit to add.
    oops, my bad as i overlooked off grid in the title so you wish to generate far more than you now consume and to add insult to injury you must overcome losses from charging the batteries in addition to other loss factors that many will say could up the requirements by 50%. adding time of year and bad weather ups things even farther and nobody can really say what the worst case will be, but we do recommend a generator to back you up for many of those cases.

    in general, you are consuming about 15kwh per day so to roughly break even, assuming that's what you want to do, then you must generate that every day. if you get 5 full sun hours per day that's 15kwh/5=3kw ptc pvs or roughly 10% higher for 3.3kw stc pvs. obviously during winter days and rainy/cloudy days you won't get that much sun so you may wish to design for 3 or 4hrs of full sun per day. it isn't exacting for one can't say for certainty just how much sun will fall for any given day, week, month, or year, but collected data for some areas does make it possible for a good guess.
  • solar_davesolar_dave Solar Expert Posts: 2,344 ✭✭✭✭
    Re: How much to go OFF GRID?

    And of course conservation is always better/cheaper than generation.
  • WindsunWindsun Solar Expert Posts: 1,164 ✭✭
    Re: How much to go OFF GRID?

    A simple question with a complex answer.

    First off, for off grid you have to design for the worst case conditions - which for most of the time will mean that the system will be way overpowered for probably 95% of the time.

    One of the biggest mistakes we see is people using the average insolation, and the average power usage - if you don't want to change your energy using habits you will have to design for peak power and worst case insolation. That is why most off-grid setups include a generator.
  • GlovesGloves Solar Expert Posts: 65 ✭✭✭✭
    Re: How much to go OFF GRID?

    I don't want to unplug, but if I were to break even at 15KW/day:

    I would need 3,000W worth of solar panels and 800Ah batteires + 2,000W inverter?
    I'm making all these numbers up here. (you could probably tell)
  • bryanlbryanl Solar Expert Posts: 175 ✭✭✭✭✭
    Re: How much to go OFF GRID?

    Tim has the base rule of thumb for a first rough draft. To extend on that 3 day 45 kwH (about half the typical average household electrical energy consumption) with some other rough rules of thumb, 45,000 watt hours needs about 4,500 pounds of battery (or Tim's 7500 AH at 12v) and at least 4.5 kw of solar panels to service them.

    Compare that to the 3kw of panel idea and 800 Ah (9600 Wh at 12v or 960#) battery idea. The solar panel isn't too far off but the reserve and backup battery capacity appears to be about an order of magnitude too small.

    Also note that a 2kw inverter is good for one circuit. Most households have several circuits. In fact, a typical household grid tie service entrance is 100A @ 240v or 24 kw.

    While a month's worth of electrical use data provides a starting point for estimating electrical use, at least a year's worth is needed to determine peaks and peak use period tenure.

    There are bunch of ideas in here. One bunch is about nominal grid tie use. Another bunch is about rules of thumb. Other posts provide insight into where those rules of thumb come from. The fun comes from trying to make all of them fit together for something that suits your interests and needs.
  • solar_davesolar_dave Solar Expert Posts: 2,344 ✭✭✭✭
    Re: How much to go OFF GRID?
    Gloves wrote: »
    I don't want to unplug, but if I were to break even at 15KW/day:

    I would need 3,000W worth of solar panels and 800Ah batteires + 2,000W inverter?
    I'm making all these numbers up here. (you could probably tell)

    Sounds like grid-tie would be the better case, no batteries involved and a higher effect use of the power all day everyday. Does Fremont require AC in summer? Your load estimate sound a bit low if so.
  • GlovesGloves Solar Expert Posts: 65 ✭✭✭✭
    Re: How much to go OFF GRID?

    I did fail to explain more specifically my dream scenario.
    • Still connected to grid
    • Using mostly my/solar energy
    • Only using grid energy for peaks
    • Paying the utilities only a few dollars per month at most.
    Not sure the (battery-less) grid-tied option is good since I have a feeling I'll only
    be using my energy during peak sun hours and at night I'll be drawing from
    the grid. (I imagine that's how it would work)

    Right now my bill is a consistent $75/mo.

    I would be trying to plan-out, buy & install a system that would pay for itself
    after x years.

    And one other thing, it would have to be AWESOME!
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: How much to go OFF GRID?

    so now it's no longer off grid?:confused: ok, but what i said would still be true.
    as to awesome, i think solar, no matter how large or small, is awesome.
  • GlovesGloves Solar Expert Posts: 65 ✭✭✭✭
    Re: How much to go OFF GRID?

    Right you are neal...
    I should call this a (LESS-GRID SETUP)

    Let's say i have:
    • 6 quantity 120w solar panels
    • 6 Trojan T-105s (225ah TOT:1350ah )
    • 2KW inverter

    how big of a chunk would that take out of my PG&E bill?
    I estimate this system would end up costing around $3,300 ish (give/take $500)
  • BB.BB. Super Moderators, Administrators Posts: 29,635 admin
    Re: How much to go OFF GRID?

    Say you have "Sacramento" type weather, 1,200 watts of solar panels, assume 0.52 end to end "off-grid" efficiency and you can use 100% of the power generated every day (practically speaking, you probably will use closer to 50%--but that is another story), using PV Watts at $0.125 per kWHr:
    "Station Identification"
    "City:","Sacramento"
    "State:","California"
    "Lat (deg N):", 38.52
    "Long (deg W):", 121.50
    "Elev (m): ", 8
    "PV System Specifications"
    "DC Rating:"," 1.2 kW"
    "DC to AC Derate Factor:"," 0.520"
    "AC Rating:"," 0.6 kW"
    "Array Type: Fixed Tilt"
    "Array Tilt:"," 38.5"
    "Array Azimuth:","180.0"

    "Energy Specifications"
    "Cost of Electricity:","12.5 cents/kWh"

    "Results"
    "Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
    1, 2.75, 49, 6.12
    2, 4.23, 69, 8.62
    3, 5.27, 95, 11.88
    4, 6.33, 108, 13.50
    5, 6.83, 116, 14.50
    6, 6.93, 112, 14.00
    7, 7.23, 119, 14.88
    8, 7.30, 121, 15.12
    9, 6.96, 114, 14.25
    10, 5.67, 98, 12.25
    11, 3.68, 62, 7.75
    12, 2.71, 47, 5.88
    "Year", 5.50, 1112, 139.00
    $139 per year in electric costs.

    And you will need to buy new batteries every ~4-8 years or so...

    There are a lot of other, and possibly better, options out there... And if you use a fair amount of power, you could be in the $0.20 to $0.40+ per kWH during the summer A/C season.

    Grid Tied can actually save you money in California (no batteries will let you get 2x the power at 1/2 the cost).

    There is are also hybrid Grid Tied / Off Grid systems... Works like Grid Tie when the power is up... Will switch to off grid mode and power your home when the utility power is down (Like a whole house solar powered UPS setup). Not a bad solution. However, there is still the costs of battery banks and their replacement.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Solar Expert Posts: 5,310 ✭✭✭✭
    Re: How much to go OFF GRID?

    I think what the OP is really proposing is a simple grid tie system that uses the grid for peak loads, but covers the bulk of his use, of 15 kwh/day average. A much smarter alternative if you were to ask my opinion. Grid tie comes at about 1/2 the cost at about twice the efficiency, yielding a 4 fold increase in bang for the buck.

    I suggest the OP read a bit about the technology/solutions/difference between grid tie and off grid system.

    Bottom line, grid tie will run ~$5/watt.

    Tony
  • solar_davesolar_dave Solar Expert Posts: 2,344 ✭✭✭✭
    Re: How much to go OFF GRID?
    Gloves wrote: »
    I did fail to explain more specifically my dream scenario.
    • Still connected to grid
    • Using mostly my/solar energy
    • Only using grid energy for peaks
    • Paying the utilities only a few dollars per month at most.
    Not sure the (battery-less) grid-tied option is good since I have a feeling I'll only
    be using my energy during peak sun hours and at night I'll be drawing from
    the grid. (I imagine that's how it would work)

    Right now my bill is a consistent $75/mo.

    I would be trying to plan-out, buy & install a system that would pay for itself
    after x years.

    And one other thing, it would have to be AWESOME!

    I do the same with grid tie, the meter running backwards becomes your battery in effect. My last bill in PHX was $23 and of that $3 was night time generation the rest was taxes and fees for the meter .... It is a much more effective use of $$$$ per watt, no battery cost or maintenance or charging loses come into play. You get every watt you generated either to use or spin the meter backwards as a bank of stored power.

    here is the PG&E grid tie site
    http://www.pge.com/myhome/saveenergymoney/solarenergy/install/netenergymetering/index.shtml
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: How much to go OFF GRID?
    Gloves wrote: »
    Right you are neal...
    I should call this a (LESS-GRID SETUP)

    Let's say i have:
    • 6 quantity 120w solar panels
    • 6 Trojan T-105s (225ah TOT:1350ah )
    • 2KW inverter

    how big of a chunk would that take out of my PG&E bill?
    I estimate this system would end up costing around $3,300 ish (give/take $500)

    It won't take anything off of your bill unless it's tied to the grid. For that you also need permits and inspections and all the assorted other stuff that goes along with doing it according to the rules.

    The alternative is to split some of your house loads off onto your solar system (separate them from your grid system).

    2manytoyz
    did that. He's got his outside lights and a couple of his inside lights on his solar system.
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: How much to go OFF GRID?

    i guess it boils down to what gt method you want,
    straight gt or battery backed gt.
    battery backed is less efficient so as to keep the batteries charged, but unless you have a problem with outages that can't be solved by a generator then go with the straight gt. straight gt will be less costs, less equipment, and higher efficiency.
  • icarusicarus Solar Expert Posts: 5,310 ✭✭✭✭
    Re: How much to go OFF GRID?

    6 120 watt Pv panels, into batteries will contribute (on average) net/net out of the inverter ~ 1.5 kwh/day, assuming "good, normal" sun. Ideal day, more, poor day obviously less. That 1.5 would be a good average in a calender year, depending on local climate.

    Tony
  • KamalaKamala Solar Expert Posts: 452 ✭✭
    Re: How much to go OFF GRID? Wrong premise.

    There are only 2, make that 3 reasons to go off... rather 4... possibly 5 (apologies to Monty Pyton's Holy Grenade) off grid.

    1. You can't get it (the grid.)
    2. It costs to much to get it.
    3. You can't get a rebate/or what ever it is called. (Tax money from fellow citizens)
    4. You have enough money to do it anyway and want to fight the lost battle.
    5. You still do what you can to justify/enjoy it.

    :confused:

    K
  • solar_davesolar_dave Solar Expert Posts: 2,344 ✭✭✭✭
    Re: How much to go OFF GRID?

    I think you have to take a capitalist point of view.

    1) assess the cost to install a system
    2) check on any govt or utility kickbacks i.e.fed tax credit of 30% (of course you have to be paying taxes for that to work)
    3) get a idea of how much of your bill you want to eliminate, a smaller system is more cost effective for just trimming the top off the bill especially if you have a tiered rate system. Lots more bang for the buck on replace those high tier rate times.
    4) Then how long does it take to pay back given the above?

    My system has an ROI of under 5 years, assuming no additional cost to keep it operating and rates stay the same (fat chance of that). If I had to do it again I would have probably stopped @ 10.4 kWh. I think I am a bit overkill, but loads do climb over time.

    We are taking another slash at conversation after the first of the year. Really the first step in any complete effective system.
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: How much to go OFF GRID?
    solar_dave wrote: »
    We are taking another slash at conversation after the first of the year. Really the first step in any complete effective system.

    I would think so! Conversation is very important!
  • GlovesGloves Solar Expert Posts: 65 ✭✭✭✭
    Re: How much to go OFF GRID?

    Yeesh... I'm going to see how well this 1 solar panel flooded battery backup goes.
    Then, I'll cross my fingers that the price of these panels goes down some. I can
    count on PG&E only charging more. :grr
  • BB.BB. Super Moderators, Administrators Posts: 29,635 admin
    Re: How much to go OFF GRID?

    At this point, solar panels, hardware, and batteries are probably nearing their bottom point. And "the government" is running out of money--so rebates and tax credits may become more iffy (unless they jack up the utility bill even more to pay "green" power producers--a very real possibility in parts of the US--already done to a degree in some states including California).

    Sorry to sound like a broken record--Have you done everything you can regarding conservation (lots of ceiling and wall insulation, double pane vinyl windows, CFL/LED lighting, Energy Star appliances/heating/cooling, replacing desktop with laptop computers, turning stuff off, etc.).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • GlovesGloves Solar Expert Posts: 65 ✭✭✭✭
    Re: How much to go OFF GRID?

    I don't know if 15KW a day is average or above average use.

    Where I live in CA, we don't need AC and not a lot of gas heating.

    Some time later i'll get a new energy star refrigerator.

    I do know that ~1.04KWH goes to keeping the reptile warm.
    I did hear that people with high electric bills are either growing pot or have reptiles.

    Turk the Iguana with a banana in his mouth:
    normal_turk_nana_yawn%7E0.jpg
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: How much to go OFF GRID?
    Gloves wrote: »
    Where I live in CA, we don't need AC and not a lot of gas heating.

    But you need hot water. Solar hot water pays for itself a LOT faster than solar electric. Maybe that's where you should be putting your efforts.

    That Turk is one ugly mutha.
  • GlovesGloves Solar Expert Posts: 65 ✭✭✭✭
    Re: How much to go OFF GRID?
    dwh wrote: »
    That Turk is one ugly mutha.

    dwh, you must have been looking at some other picture. The picture I posted was
    the one with the brightly colored happy lizard.

    Solar water heating... what's involved???
    I just looked at my water heater, it's gas.
    http://www.mysears.com/Kenmore-Power-Miser-9-40-gal-Gas-Water-Heater-reviews?tab=details

    I looked into on demand heated water, that takes DOZENS of amps and hundreds
    of watts to get past room temp. (and they break a lot). What's a practical way of
    heating water with solar?

    My clothes dryer is also gas.
  • BB.BB. Super Moderators, Administrators Posts: 29,635 admin
    Re: How much to go OFF GRID?

    Out of this thread of lots of solar PV, thermal, and other DIY project information:

    Working Thread for Solar Beginner Post/FAQ
    Solar Thermal can be a nice source for space heating and hot water... And usually is "cheaper" per kWhr/BTU vs Solar PV Electric. Also, Solar Thermal lends itself very well to do it yourself projects. Note, these are plumbing projects and have their own issues (leaks, pump failures, installation issues trapping air, anti-freeze, storage, heat exchangers, etc.):

    Solar Shed and other Solar Thermal Links

    A good place to start reading is Home Power Magazine... They have a free past issue online--and have a lot of articles you can read for free. I don't always agree with them and their reviews--but they are a fun and enlightening read:

    Home Power Mag
    I have been an advocate of solar thermal for almost a decade, but I'm rethinking this with the new generation of heat-pump based ( energy star ) hot water systems.

    With COP's of about 3-4 and one third the cost of typical solar thermal systems this would seem to be the best choice for total cost of ownership. I also like the fact they will cool the surrounding area for free great for cooling the garage in the summer!

    Solar thermal is far from maintenance free and its a major hassle to run the plumbing for roof mount collectors and worry about roof penetrations and leaks. The heat pump HW tanks is literally a simple swap with a standard domestic electric HW tank.

    http://www.geappliances.com/heat-pump-hot-water-heater/

    http://www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=12840

    At a minimum, its nice to have a new choice in saving energy!

    Gas/Propane tankless water heaters are certainly an option for saving energy--especially for "low usage" type situations.

    Electric tankless heaters--forget them for off-grid use, and even on-grid use can be a big issue (can cause house lights to flicker/dim as the heater elements activate/deactivate).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • GlovesGloves Solar Expert Posts: 65 ✭✭✭✭
    Re: How much to go OFF GRID?

    I take my showers in the morning.
    There hasn't been decent sun for 16 hours.
    Doesn't the water get cold by then?

    I guess I could try to switch my routine to
    evening showers.
  • techntrektechntrek Solar Expert Posts: 1,372 ✭✭✭
    Re: How much to go OFF GRID?

    One catch for the tankless units, if you have lots of minerals in your water they will clog up fast. Best to stick with a tank then.

    As for retaining heat, I have my 40 gallon electric tank on a timer and its wrapped in R-22 insulation on all sides/top. It is only on for 2 hours in the early morning and 4 hours in the evening. There have been Saturdays where we've worked in the yard and haven't gotten in the shower until late afternoon, before the timer kicked on. We can still get two full showers even though it has been off for 11 hours. I'm sure I could get at least one full shower after 17 hours off.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • icarusicarus Solar Expert Posts: 5,310 ✭✭✭✭
    Re: How much to go OFF GRID?

    If you have lots of minerals in your water, install a sacrificial anode in your water heater line to prevent scale build up.

    Tony
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