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Solar panels to charge MS

I realize this is a little off topic, but I get the feeling there are a few experts here on solar panels. How big do the panels on your house need to be in order to be effective? What cost are we looking at? Is it worth it financially if electricity is .09/KWH where I live?


Unless you are in the Southern Hemisphere, then it is all upside down.

Summer starts in September, there. It's so hot in December, they celebrate Xmas with Santa Clausless.

Our friend Jennifer gave us her actually numbers for her 6.5kW system. Using her numbers, I calculated what I should expect from a 10kW system. Savings are based on 10cents/kw October-April, and 13cents/kw May-September. Does this seem right to people?

6.5kW 10kW
Jennifer Jupiter
kw kw Money Saved
Jan 261 400 40
Feb 417 638 63.8
Mar 643 983 98.3
April 832 1272 127.2
May 1113 1702 221.3
June 1196 1829 237.8
July 1212 1854 241.02
Aug 1052 1609 209.2
Sept 1039 1589 206.6
Oct 726 1110 111
Nov 420 642 64.2
Dec 409 625 62.5
Total 9320kw 14253kw $1682.92

Average 776.6kw 1187kw $140
Daily 25.9kw 40kw/day

crap, it didn't save my nice formatting....

Rows are as follows, using the Jan row as an example.
Jan 261kw for Jennifers 6.5kW system, 400Kw projected for 10kw system, $40 saved.

That data seems very consistent with my actual data.
You can check out hundreds of systems (including mine) online at the Enphase website:

It will show the actual production data since each system was installed.

@Brian H
Also, while the days are longer in the Summer (so the sun is up for more hours), the actual total insolation (sun that hits the earth) or hours of full sun is often less in the Summer due to the amount of clouds. This is very evident in Orlando where is rains almost ever afternoon (when the Sun is near its optimal height/intensity).
You can get data on the usable hours of sun per day here:

We built our system a few years ago at around $7 per KW, 65% of it taken off state or federal taxes. We buy electric around 15 cents per khw but have a 5 year contract that pays us 20 cents a kwh. We built large enough for house use and put in the hardware for expansion for ecar in future.

After the system is paid for we essentially have free electric for life, perhaps free car fuel also!

Blog of the buildout here:

use the <pre> tag to save formatting. Reduces font size, though.

I live in So Cal and have a 18,000 gal pool. I keep the pool pump on 2.5 hrs in the winter and 4 hrs in the summer. The key is the pool pump. My brother-in-law is in the pool business and guided me on the pump. Since I changed pumps there have been improvements with variable speed motors and other developments. Try to find someone who knows pump motors and you may be able to cut a lot of that electricity usage, even on a large house.

Clearly pool pumps are the biggest users of electricity, with A/C coming in second. I keep daily records of solar energy produced by my system and my usage. My Model S averages about 12 kWh/day and I am putting an average of 40 mi/day on the car.

It's impossible to answer this question without a copy of your electric bill and a more complete understating of your electricity usage patterns. The goal of most PV owners is to get sufficient annual production to lower their electricity consumption to the lowest tier, a "bang-for-the-buck" solution. On the other hand, with the price for individual solar panels so low, the approach I took was buy a large enough system to meet 100% of my electricity consumption today. (You never know, maybe someday I'll want heated floors or an electric water heater)

Since electricity rates will increase - they are certainly never going to fall - just go for it rather than endlessly wrangling over the decision. Solar systems are cost effective and will guarantee somewhere around $0.07-0.09/kWhr for the next 20 years. Your electricity company will absolutely be more expensive over this period. It's unwise in the long run not to get solar if you have a good roof with no shade. It adds close to 100% of the investment to the value of your home. And if you are getting solar - go for the max - less regrets.

Solar Panels are going to help always. The electricity bills are never going to be same. But the solar panel is just one time investment. I have one at my home too. You may get it from Sterling if you are planning to buy. There is also not much maintenance cost.

I got my panels from Solar City. The system was sized for my current energy usage. Anyone know if they'll come out and add more/write a new contract if I want to purchase a Tesla? Any one asked Solar City?

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