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  1. #1
    Join Date
    Aug 2017
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    Oil Boiler vs Electrical Boiler

    Hello group,

    We currently use 1000 gallons of oil to heat our home and hot water for a year. I"m going to assume the boiler is around 84%. We just installed a solar system that can provide 29k kilowatts on annual basis. I tried to do some math as far as converting oil usage to kw usage but I'm not sure I'm looking at it correctly. I calculated we "use" 139,000,000 BTUs based on 1 gallon of oil creates 139,000 BTUs. I took 84% of that number and I then converted using one of those online calculators to kw. I got 34,218. So it is correct that our system will not provide enough kw to cover our heat and hot water? Thanks so much.

    Georgina

  2. #2
    Join Date
    Feb 2017
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    New York
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    Ok, by no means am I an expert in this, but I think this needs to be looked at a little differently. I would also like to get the ball rolling, so if anyone disagrees or has anything to add, please do.
    This needs to be looked at a little closer than total numbers. The way you are looking at it now is suggesting that you have 100% storage of the power you make. As we all know, the only thing that is 100% is death and taxes!
    Electric boilers are a substantial electrical load. It comes on in an on-demand basis. Solar power isn't considered an on-demand source. Say it's been quite cloudy and cold, where will your power be? You'll use up your battery storage and be out of heat.
    You also need to make sure your inverters will handle a load that large. Just a standard electric hot water tank can pull up to 6kW! That would be a huge inverter to run it. I'm assuming you have a 24V system. That would be over 250 amps drawing from the batteries.
    Now, if you can parallel to the grid to offset your power usage but still have city power available, then electric may be the way to go. I believe that type of setup is quite costly.
    -----Stop, step back, relax and have another go at it.-----

  3. #3
    Join Date
    Mar 2013
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    Billington Heights, NY
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    29 KW a year? What size are these panels?
    Experience - knowing when to get the hell out of the way and plug your ears. "Don't be a sissy. Turn it on!"
    Poodle Head Mikey - "the world is well populated with the unknowing and the uncaring and the stupid."

  4. #4
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    Feb 2017
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    New York
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    What size is your system? Some quick figures, it seems like it's around 20kW... assuming that your 29,000kW a year is correct.
    Last edited by BennyD; 08-13-2017 at 11:33 PM. Reason: Typo
    -----Stop, step back, relax and have another go at it.-----

  5. #5
    Join Date
    Mar 2013
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    Billington Heights, NY
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    Quote Originally Posted by BennyD View Post
    What size is your system? Some quick figures, it seems like it's around 20kW... assuming that your 29,000kW a year is correct.

    Is it 29,000 KW a year or 29KW a year? was 29k kw a typo?
    Experience - knowing when to get the hell out of the way and plug your ears. "Don't be a sissy. Turn it on!"
    Poodle Head Mikey - "the world is well populated with the unknowing and the uncaring and the stupid."

  6. #6
    Join Date
    Mar 2015
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    Medford, N.Y.
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    What size Solar Panels do you have?How many? Are all of these panels the PV or Hot Water Storage? You have Battery Back-Up, Power Storage? Are the Panels "tracking/moving/follow the sun" type?

  7. #7
    Join Date
    Aug 2017
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    Thread Starter
    Thank you for the responses so far. Some clarifying points. We are still tied to the grid, we do not have batteries. We have upgraded our home service to 400 amp. Our panels are ground mounted but do no move. They are very large but I'm not sure the exact dimensions. Obviously they are on an angle but it is at least 10 ft tall and close to 20ft wide. All the panels are PV. And lastly the annul output is 29,000kw. Thank you!

  8. Likes HVAC_Marc liked this post
  9. #8
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    Mar 2013
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    Billington Heights, NY
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    If you dont have a storage system I cant see how you're going to do anything during a blackout/night.


    during normal times are you drawing back from the grid in the hopes of an equal offset?
    Experience - knowing when to get the hell out of the way and plug your ears. "Don't be a sissy. Turn it on!"
    Poodle Head Mikey - "the world is well populated with the unknowing and the uncaring and the stupid."

  10. #9
    Join Date
    Jan 2015
    Location
    Iowa
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    *You have not provided enough information to make a good recommendation.
    *You will need more than just a 400 amp service to take advantage of the solar array.
    *There are rebates and tax exemption you can take to offset costs (talk to utility and tax guy)
    *You do understand as you have described your system you will only be able to draw power from it for only a small percentage of the daylight time (like 20%)
    *You probably should be looking at a geothermal installation (depending on your climate maybe a backup heat system)
    *Have you talked to your electricity provider? Have you signed a power producer agreement with them? They will tell you what you need to install. Because when you are creating power and have excess power the electric company will buy it from you.
    *But by the same token in cloudy, overcast and after dark hours you will draw power as you always did.
    *Unless you live in a really remote area I have to believe that electricity is cheaper than fuel oil. Plus you may not notice it now the whole house will smell better, never seen a oil burning house that some oil smell was not noticable.
    *In the foreseable future LP gas will be cheaper than Oil or Electric (LP gas fired boiler)
    *if you are looking at being independant and not need the grid, you should look at the ability for adding a wind turbine and a back up generator.
    *There are relatively inexpensive backup generators that run on LP gas
    *if you have the ability to sell power back to the electric company I would remain tied to the grid.

    Find several contractors (you will need both Electrical and an HVAC contractors) in your area and have them discuss a whole plan. Oil and straight electric boilers are not the way to go (geothermal is) for what you say you have already done and just guessing what you would like to do.

    Good Luck

  11. #10
    Join Date
    Sep 2005
    Location
    Atlanta GA area
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    Hmmm...

    Lets start out with some basics:
    Assuming (we have not seen anything, just guessing)...
    Most PV panels are 3' x 5'... so your approx 10' x 20' may well be 2 rows of 7 panels... or 14 panels.
    Panels can produce between 250-300 watts each... so lets be optimistic (assuming FULL SUN... panels ONLY produce full power on a totally cloudless summer day)...
    You have the potential for 21 x 300 = 6300W output or 6.3KW output.
    That is about enough to run a standard water heater and a few light bulbs... again assuming FULL SUN!

    It is potentially possible you 'could' heat up the water and the house during the day... and partially get by during the night...

    However we have one more issue to consider: The farther north ones location is... the less power the panels produce... and in the cold months (winter) that power is reduced even more.

    Sooo...
    Might want to do some more research!

    Personally... I would NOT want to be totally dependent on one form of energy for heat... especially in a cold climate... think what would happen if that source failed for some reason (yes, it happens).
    At the very least... keep a fireplace or a wood burning stove and lots of dry wood available.

    Nothing like a super energy efficient (and VERY costly) high tech house... and it does not work due to a technical glitch... so the occupants are COLD...
    GA-HVAC-Tech

    Your comfort, Your way, Everyday!

  12. #11
    Join Date
    Sep 2015
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    Ok, actual annual average energy collected by solar systems is approximately 17% of installed capacity times hours in a year. That changes with local solar conditions. The generation will swing between more in summer than in winter.

    Capacity is kW or kilowatts. Consumption/generation is kWh or kilowatt hours. A 1000 watt bulb consumes one kilowatt hour (1kWh) per hour.

    If your photovoltaic system has a 29 kW capacity, I expect you will generate 17% x 29 kW x 8760 hours per year or about 43,000 kWh annually.

    Going backwards, if your system provides 29,000 kWh per year, then I expect your capacity is 29,000/17%/8760 hours or about 20 kW.

    Solar power is generated throughout the year. I can't imagine how electricity generated in August can be used for heat in February.

    IMHO, if available, gas fired boiler is a better conversion.

  13. #12
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    Aug 2002
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    Southold, NY
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    The only A/C Heat Pumps that stand a chance with solar are Mini Splits. Even then getting anything running on solar is difficult.

    Gas heater draws a lot less power.

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