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Old 05-21-2014, 05:23 AM
 
Location: Vermont
5,439 posts, read 14,742,061 times
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The OP is not asking about battery systems or battery backup systems.

Quote:
Originally Posted by yellowsnow View Post
You have good logical questions and I should have given more details. Sorry!

I do live in Nevada, Las Vegas to be exact. I want the PV system because I want to be cool in the summer and not worry about the electric bill. NVEnergy was recently bought by Warren Buffett and friends and historically his utilities go up 10% per year and I know I can't afford a 50% increase in 5 years. I am quite tired of sweating when we have no shortage of free sunshine.

My house is 1 story, 1500sf, and I have a 5ton ac unit on the roof. I already have solar hot water up there too. I will be grid connected so there are no batteries needed. NVEnergy will not pay money for power I return to them but I do get a bill credit. I may not generate enough power during the hottest part of the year but I should have enough of a credit built up over the winter to make up the difference. At least that's the plan.

The quotes I've gotten so far range from 30K to 21K for an 8KW system. The system will be on a S facing roof with no obstructions. It will get a lot of sun year round. I am supposed to get back 30% of whatever I spend on my taxes.

Will NVEnergy credit you the same rate per KWH as they charge you for KWH you purchase from them? A lot of companies do not.

How many KWH do you use per year? If the system is 8kw, how many KWH do these companies say you will generate per year (I'd say 6 sunhours*8kw*365 days= 17520 KWH on the high end)? Since they do not pay you, only credit, you want to size it so you make basically exactly as much as you use. There is no advantage to a larger system unless you intend to use more later.

As technology becomes more efficient (for example more efficient AC), I'd say the likelyhood of this is low. Do you know what the SEER rating of your AC is? This is another factor to consider because it could be cheaper to upgrade your AC than to get solar--however you could also do both

Last edited by joe moving; 05-21-2014 at 05:36 AM..
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Old 05-22-2014, 12:07 AM
 
Location: Las Vegas
13,837 posts, read 25,215,602 times
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Quote:
Originally Posted by joe moving View Post
The OP is not asking about battery systems or battery backup systems.




Will NVEnergy credit you the same rate per KWH as they charge you for KWH you purchase from them? A lot of companies do not.

How many KWH do you use per year? If the system is 8kw, how many KWH do these companies say you will generate per year (I'd say 6 sunhours*8kw*365 days= 17520 KWH on the high end)? Since they do not pay you, only credit, you want to size it so you make basically exactly as much as you use. There is no advantage to a larger system unless you intend to use more later.

As technology becomes more efficient (for example more efficient AC), I'd say the likelyhood of this is low. Do you know what the SEER rating of your AC is? This is another factor to consider because it could be cheaper to upgrade your AC than to get solar--however you could also do both
I was told it's the same rate. My AC is a 13 but seer is relative here because it is based on cooling with an 82 outside temp. Sometimes the outside temp here is close to 120. The unit was replaced in 2009.

My motivation to do this is to lower my monthly bills and be cool in the summer. The way I'm seeing this is that if I replace my AC it's MAYBE good for 10years. And I am still up for that probable 50% power increase in 5 years. I have never seen our public utility commission turn down a proposed rate increase. NVEnergy gets what they want. I am better off making my own power than using theirs more efficiently. And the solar should last 20+ years.

I used 14,225 KWH last year BUT that was setting the thermostat to the misery point all summer. I want to be cool! And in Las Vegas, the 6 sunhours is probably accurate. Plus, in the future I will most likely heat pump the pool and perhaps get an electric scooter or something like that. So I am planning a bit for future consumption too.
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Old 05-22-2014, 07:39 AM
 
Location: DC
6,505 posts, read 6,426,164 times
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Here is NREL's model .

PVWATTS: Nevada - Las_Vegas
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Old 05-22-2014, 09:38 AM
 
Location: Las Vegas
13,837 posts, read 25,215,602 times
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Quote:
Originally Posted by DCforever View Post
Here is NREL's model .

PVWATTS: Nevada - Las_Vegas

I'm not quite sure what this is/what to do with it. But thank you.
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Old 05-22-2014, 09:54 AM
 
Location: Vermont
5,439 posts, read 14,742,061 times
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Do you get 100% of your water from solar?

As long as they pay you what they charge you, and you create similar KWH as you use, you should be good. I would say 8 KW seems like the right size., but you might consider reducing your overall consumption first or at least compare payback time periods .

One thing that is easy to do (if you can get them for the right price) is to change light bulbs to LEDs If you have not already done so. However, going from CFL to LED is not a big drop in power if you already use CFLs (I personally hate CFLs and got rid of them entirely, but tolerate LEDs).

Going from SEER13 to SEER20 should reduce consumption by 65% if I understand correctly. That is Seer13/Seer20 = 0.65, so if you electric bill caused by current AC is say, 9000 KWH a year, then SEER20 will use 9000KWH*.65 = 5850 KWH, at .10 per KWH (?) would be ~$300 a year savings. I have no clue what a 5ton SEER20 setup is going to cost you though. This may qualify for a 30% tax credit as well.
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Old 05-22-2014, 10:02 AM
 
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I didn't think there was any savings between CFL and LED. Just that LEDS didn't have mercury in them.
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Old 05-22-2014, 11:07 AM
 
Location: Vermont
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I think that is right that they use about the same power. so if yellowsnow is already using CFLs, that is not going to be a place to reduce energy.
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Old 05-22-2014, 11:48 AM
 
Location: DC
6,505 posts, read 6,426,164 times
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Quote:
Originally Posted by yellowsnow View Post
I'm not quite sure what this is/what to do with it. But thank you.
Enter your system size and location. It will tell you month by month how much energy your system can be expected to generate.
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Old 05-22-2014, 02:04 PM
 
Location: Volcano
12,971 posts, read 23,536,189 times
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Quote:
Originally Posted by Dakster View Post
I didn't think there was any savings between CFL and LED. Just that LEDS didn't have mercury in them.
Quote:
Originally Posted by joe moving View Post
I think that is right that they use about the same power. so if yellowsnow is already using CFLs, that is not going to be a place to reduce energy.
Typical bulb sizes that give the equivalent light to a 60 watt incandescent bulb are 14 watt CFLs or 10 watt LEDS.

For 100 watt incandescents, the equivalent CFL replacement is 26 watts, LED is 19 watts.

So, no, replacing CFLs with LEDs doesn't make a huge difference energy-wise in terms of solar energy planning. You can wait until the CFLs naturally burn out.

Where LEDs really have it over CFLs is that they last 5X as long, and aren't enclosed in a fragile glass tube, so they are more durable, and can cost out at 1/2 the total expense of CFLs over their projected 50,000 hour life.

As far as the mercury in CFLs, they have only a tiny fraction of the amount found in the traditional tube type fluorescents we've had around us all our lives, and the danger from them is vastly overblown. If you happen to break one, don't breathe it in. That's all.
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Old 05-22-2014, 05:38 PM
 
4,718 posts, read 8,941,768 times
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I always thought that the mercury in CFL was worse for the disposal environment when they are discarded in the hundreds to thousands. Not that they were harmful in your house. I have most of my lights CFLs at the moment. I bought cases of them when HD had them on sale. I have a 5 lights in the house that CFLs just won't work in. One is outside on a lamp pole - and apparently it needs a rough service bulb. Haven't found a rough service CFL or LED yet. And the other is a fan, even though I've replaced it, the wiring, and the SWITCH, for some reason CFLs and LEDs flicker in it. I gave up and just use it sparingly and with incandescent bulbs. I guess the ghost of the house doesn't like those types of bulbs there...

Anyways, if the cost analysis doesn't work out, you just have to wait until the pricing or the extra power buy back does. Unless you just want to "feel" good about not using your power companies power. I wonder if at one point you could sell your credits to someone else? I know that in AK, they won't buy the extra power, but if you have other power bills in your name with the same company you can transfer the credits over...
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