[ausev] Residental Solar Power ROI

Fri Aug 8 11:38:59 GMT 2008

No, 10 to 20 KWh a day is not a lot.... but if you are using 6KW an have a solar system that can barely keep up, then you would end up with bills much larger than 10 to 20KWH for a day; one hour would burn 30% to 60% of that estimate.? 10 to 20KWH per day would come out to 300 to 600 kwh per day.? In looking at your numbers below, that would say that you are likely using 20kwh per day as a minimum, like you showed, 34kwh.

We live in a house built before 1960 with an AC unit more than 30 years old.?? We do things to conserve, and we endup using on average under 500kwh per month.? Our low in the last year was ~220kwh.

-----Original Message-----
From: Dustin <ullearn at gmail.com>
To: AustinEV News Announcements and General Discussion <ausev at austinev.org>
Sent: Thu, 7 Aug 2008 11:12 pm
Subject: Re: [ausev] Residental Solar Power ROI

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 

To: 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> 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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