[ausev] Residental Solar Power ROI

Fri Aug 8 04:28:34 GMT 2008

Just a spot check -- I had 2251kWhr last month and 1075 the month of 
December (that should be one of my lowest)
Our house is 14 years old, but we've got a lot of SF to cool down.

m

Dustin wrote:
> Greg,
>  
> Is 10-20kWh a day allot? 
>  
> My wife and I live in a 2006 built home and tend to keep the A/C 
> higher and the lights off during most days.  But my #'s below would 
> say that on average we use 34 kWh a day.
>  
> For my house my yearly energy usage is 12,267 kWh; with a high of 1577 
> kWh per month; low of 616 kWh per month; and a average of 1022 kWh per 
> month.
>  
> -Dustin
>
>     ----- Original Message -----
>     *From:* gregmckay at aol.com <mailto:gregmckay at aol.com>
>     *To:* ausev at austinev.org <mailto:ausev at austinev.org>
>     *Sent:* Thursday, August 07, 2008 6:30 PM
>     *Subject:* Re: [ausev] Residental Solar Power ROI
>
>     Gosh I don't want to tell all those folks that used their Prius
>     for back up power in Florida after the Hurricanes that it didn't
>     really work for them.....
>     One of the key components that you left out of the equation is how
>     to get the power from your batteries to the house as AC.
>     For the Prius it is easy.  Use a standard 12v 1000w inverter.  
>     ...and remember we are talking about BACK UP power, as in for
>     emergencies....  so 1000w will do most folks just fine.   That is
>     eactly why the Honda 1000 and 2000 watt generators are selling so
>     well.
>      
>     When I have the EV up and running I just can't see using all of it
>     available capacity to power the house for one day, or maybe part
>     of the day.... and at the end of it all have a dead vehicle.
>      
>     There is no question that a small amount of solar can make a big
>     difference... as long as the system gives you power when you need
>     it.  our 100w guerilla system made an absolutely huge difference,
>     much large difference than we would ever have expected.
>
>
>     So if I were looking at using my EV as backup power, and I was
>     going to have to make an investment in an inverter to get it all
>     to work, I might invest in a small generator instead and get a lot
>     more backup power.
>      
>      
>     You should look into a more efficient Air Conditioner.  Our AC
>     system is more than 30 years old and we use less than 500kwh of
>     electric most months.  When we replace it, it will be with a 12v
>     system that can be supported by its own solar even when the grid
>     is down.
>
>     If you are chewing up 6KW of electric at any given time during the
>     day you are using a bunch.
>     ...that would be more than 10 to 20KWH a day.....by a lot !!
>
>
>
>     -----Original Message-----
>     From: Brian Lasseter <blasseter.cmpe01 at gtalumni.org>
>     To: AustinEV News Announcements and General Discussion
>     <ausev at austinev.org>
>     Sent: Thu, 7 Aug 2008 5:20 pm
>     Subject: Re: [ausev] Residental Solar Power ROI
>
>     On Thu, Aug 7, 2008 at 1:30 PM,  <gregmckay at aol.com <mailto:gregmckay at aol.com>> wrote:
>     > How many AH could you get out of th EV's battery?
>     > Would you want to risk discharging too deeply?
>     > ....and then you have a vehicle that needs charging afterwards anyway....
>
>     In my personal case... The 18x 8V 170Ah batteries in my car store an
>     energy of 24.48kwh.  Of which, about half is usable.  I use 10-20kwh
>     in my house on an average day, so 12.24kwh would be more than enough
>     energy to get me through the night before the sun comes back up to
>     recharge the car.  (Especially since the Air Conditioning doesn't run
>     as much at night.)  Solar panels on the roof hooked up to a high
>     voltage electric vehicle power pack will keep you running for almost
>     forever.
>
>
>     > I know this is not a hybrid droup, BUT something like the Prius is perfect
>     > as a UPS backup.
>     >
>     > You hook an inverter to the 12v aux battery, fill the gas tank, and walk
>     > away.
>     > As you draw down the 12v battery through the use of the inverter, the car
>     > supplements the 12v with the HV battery.
>     > As the HV battery soc gets low the car is monitoring it and starts the ICE
>     > to recharge the HV battery,... and then the ICE turns off.
>     > ...and you can go like that until the gas tank empties....
>
>     A 10 gallon fuel tank has an energy equivalent of 345kwh of power, and
>     since the Prius will only let you pull 1500watts from the 12V side
>     before car stops supplementing the 12V battery, you could pull 1250W
>     with an inverter for 276 hours (or 11.5 days) before running out of
>     gas.  (Assuming perfect energy conversions... I don't know the
>     efficiencies of the Prius going from gasoline to engine to generator
>     to DC-DC converter to DC-AC inverter.)
>
>     However 1250W of power doesn't get you very far.  You could run a few
>     lights and a laptop.  You could run a microwave if you unplug the
>     lights and the laptop.  You wouldn't be able to run your fridge, or
>     the air conditioning.  You could not use it as a UPS backup for a
>     whole house.  One 15A circuit would be all I would trust it to run.
>
>     I run a 6656W solar system, and it can barely keep up if I'm at home
>     on the weekend with the air conditioning on, watching TV, and cooking
>     some lunch in the oven.
>
>
>     -- 
>     TTFN,
>     Brian "Lasso" Lasseter
>
>     "No Sane man will dance." -Cicero (106-43 B.C.)
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