Time to Grid Tie?

Here is where I'm at , off grid, 48V system, Xantrex system, 16 Trojan batteries, three MPPT60 chargers, 10,000 watts PV's, 10KW backup gen-set, by 10 am the batteries are topped off and in float already(aprox 60.3v), Should I spend the money and feed back in to the grid? the batteries carry us through the night no probblem, might add more PV's if I don't connect to grid. It will cost about 25K to get power down to me. Wife thinks not, my electrician thinks that by his calculations in 10 years a 40K+ payback.... I'm on the fence , any input form others with a lot more knoledge would be helpful, and maybe make my decision easier. Zipcode is 54501, true south facing fixed on a 4/12 Pitch roof , minimal shading. Last Sunday it was overcast and the three controllers read at about 2500w each at 11am.
On The Fence, Help

Comments

  • BB.BB. Super Moderators, Administrators Posts: 28,141 admin
    Re: Time to Grid Tie?

    I would not suggest that you pay to bring in the grid just so you can feed excess power back.

    The reasons I would think about connecting to grid include:
    • Bringing power to your property increases the value of the property if/when it is sold.
    • It allows you to either downsize or remove your battery based off grid system to reduce maintenance costs (still use for backup and/or install backup genset).
    • As you get older, will you and/or your spouse be able to maintain the system?
    • Bringing in the grid is only getting more expensive--If you will eventually need grid power (getting old/selling property), would it make sense to get it now? Could you spend some time working with neighbors to split the costs of bringing in the power?
    Grid Tied solar is probably going to be "leaving us" as a viable/cost effective source of power over the next 10-20 years. GT Solar does not make sense to utilities (customers buying power at $0.10 a kWH off peak and selling to utilities at $0.30 per kWH peak). You will probably see power prices migrating (in my case) from $0.10-$0.30 per kWH and $4.50 monthly connection fee to $0.05-$0.10 per kWH and $40-$96+ per month connection fee (doubling of base connection charges is already starting to happen here, and the $40-$96 connect fees are already happening in a few locations).

    For the "average" electrical consumer, the changing of the rate plans may not affect their total monthly bill. However, for people that conserve and/or have GT solar, it kills the rate of return. More or less, ~1/2 of our power costs are "fixed" (local distribution costs) and the other 1/2 is the actual cost to generate the power.

    If you keep your power usage relatively low (conservation)--There may be some point (sooner than later) where you would be better off dropping your utility connection rather than keeping it (once you bring it to your property). And, at that point, perhaps there will be enough installed base of off grid solar power to make it worthwhile to call a "local" solar service tech for maintenance as you and your system age.

    -Bill "my two cents" B.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Time to Grid Tie?

    What you need to do at this time is figure out what it will cost you to replace your battery bank after somewhere between 3 and 8 years, depending on how well you are able to take care of your batteries. That will give you the minimum possible cost of your off-grid PV system on an upkeep basis, regardless of how much power you will use.
    Compare that to the cost of whatever energy you will use from the grid and the amortized cost of the hookup.
    At that point I would expect that the result will be in line with your electrician's payback estimate, but without seeing your actual numbers, it is just a guesstimate.
    If you have to add more PV, including more CCs and also have to run a generator from time to time during the winter, all of that will add to the PV system cost.

    When calculating the ongoing cost for power from an off grid system, many users do not properly account for battery replacement.
    I think that BB is correct in his speculation that if you do plan to sell the cost of bringing in grid power now will give you a fair return in the price of the property at sale. But check with a local rural property realtor for confirmation on that.
    SMA SB 3000, old BP panels.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Time to Grid Tie?

    #1: What, if anything, will the utility pay for any surplus power you produce and sell to them?
    #2: Determine how much power you use vs. how much you could potentially produce to determine what that surplus may be.
    #3: At cents per kW hour it will take a long time to pay back $25,000 investment no matter how much surplus you have from your 10kW system. (40kW hours per day here is worth $4: to pay back $25,000 would take the entire production of the system for 17 years.)
    #4: Other advantages of having the grid that Bill outlined have value not easily quantified.
  • Wis03BladeWis03Blade Registered Users Posts: 20
    Re: Time to Grid Tie?

    Only person on the road. so no neighbors to share. Last time I inquired the pay was same in , same out at .11 KWH up to a 20kw system. System 3yrs old now, set up now to only use the top 30% of batteries never dipping below 70% of that full charge. Gen-set is a 10kw that does turn on weekly for maintiance runs, and about once a week when there's heavy snowfall, I've only have to add water about every other month since new. They are flooded batteries , and I have been told that with low consumption and good maintiance 15yrs is not out of the norm. I do Equalize every month via only one battery bank at a time. I'm about 2 miles off the main road , so it's a considerable distance. We never origianly intended to feed back in, when we had to make the decision between running power down, or going off-grid, we only had 9 PV's and one charger at that time and were told that would do it ( and the price at that time was a wash) . We could not make it overnight in the winter with out generator running, so every year we've added so that can handle the consumption , summer has never been an issue, but winters can be down right mean. But now with the system basicaly shutting off , it seams like a waste to just loose that input. The grid had not been that great, there were three days this last summer that our area was powerless ( not us of course)
  • zonebluezoneblue Solar Expert Posts: 1,218 ✭✭✭✭
    Re: Time to Grid Tie?

    Well if you decide not to connect, can you find other uses for the power? Hotwater, cooking , electric car etc?

    One day, some bright spark might produce us a nice wee hydrolysis unit.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • Wis03BladeWis03Blade Registered Users Posts: 20
    Re: Time to Grid Tie?

    everything else in house is on LP ( the Boiler for the floor heat, Generator, the on-demand hot water, the backup furnace,and the stove) I did some Charge controller history log viewing. problem is that only logs power in, not after the controller shuts (prior to sundown) down due to full batteries and no need for additional PV input. So that makes it extremely difficult to determine what actually is lost. I guess for now I'll leave it as is, one good thing is that I currently have too much PV, not that I need more.
  • BB.BB. Super Moderators, Administrators Posts: 28,141 admin
    Re: Time to Grid Tie?

    Can you bring the power (cost effectively) to the edge of your property?

    And then run a relatively small gauge wire from the edge of your property "cheaply" to your home? And limit the power to say, 1,000 watts maximum (possibly step/step down transformer to bring higher or medium voltage on your "personal" line, perhaps even a single wire with "ground return") to the home.

    Basically, keep your off grid power system, and use the X,XXX watts from the small feed just like a small generator to keep the battery bank full (and let the batteries support the high surge current/heavy short term loads).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Wis03BladeWis03Blade Registered Users Posts: 20
    Re: Time to Grid Tie?

    There is a power box at the end of the road, I inquired , and it was placed there when the road was constructed for future hookups for anyone on my road wanted power. I can run a meter post all the way up my drive way according to my electrician. There must be a unlocked manual shut off placed at that location , but then anyone could come along and snap it off. ( that area doubles as the snowmobile trail) It's still almost 1 mile (underground only) run from that distribution box to that meter post location. I wouldn't feel comfortable with that. I know that as soon as I pay to run that power down, other property owners( who have inquired about power via We Energy) between box and me will then just hook up at minimal expense, they so not share initial expense and i do not get reimbursement ( We Energy policy) for there run of the wire. Is there any way to meter what the PV's are producing including the amount not recorded at shutdown. Lets figure that in the high sun months my 10kw PV's are full sun from 7am-7pm ( 12hs daily) with out my consumption. at .11 per Kwh for 4 months, my calculations bring me to about $40 a month or 1600 for that time frame, That's 16 years break even. Seems pointless . Even if I max PV's to 20kw ( my cost now i s 1.66 per watt installed) That's an additional 17K on top of the 25k for power, and only runs my monthly income to $80 . Am I correct in my calculations?
  • BB.BB. Super Moderators, Administrators Posts: 28,141 admin
    Re: Time to Grid Tie?

    If you have cheap power costs--Yea, it is difficult to make economic sense for GT connected solar.

    For me in California, we can pay from $0.09 to ~$0.50 per kWH (>1,000 kWH per summer afternoons). And we get to sell back at retail (buy power off peak at $0.10 to $0.40 per kWH, sell at $0.30-$0.50 per kWH at summer peaks).

    And, with the coming changes in billing over the next years or decade--You might see your monthly fixed charges skyrocket, and the per kWH pricing drop--Which makes GT solar (and conservation) is more financially problematic.

    When power drops to $0.05 per kWH and fixed monthly fees go to something like $50 to $100 per month.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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