13 Weeks Solar Production

Our rolling 30-day average production is 287 KWH, which is higher than the target average of 228.6 KWH to achieve the CSI estimated annual production for our system.

Total After 13 Weeks:
Production: 750 KWH
CO2 Saved: 1,245 lbs
Estimated Savings: $150.00

Weekly Production History:
Week 13: 55.70 KWH
Week 12: 65.83 KWH
Week 11: 74.17 KWH
Week 10: 72.13 KWH
Week 9: 53.68 KWH
Week 8: 50.01 KWH

Monthly Production History:
April 2011 (partial): 245.98 KWH
Mar 2011: 262.25 KWH
Feb 2011: 206.07 KWH
Jan 2011: 38.50 KWH (1/26-1/31)
System Size DC (STC): 2.28KW
System Size AC: 1.93KW
System Size AC (California CSI rating): 1.63KW
Panels: 10 Sunpower Serengeti 228 Watt
Inverter: 1 Sunpower 3000M (SMA Sunny Boy 3000 rebranded under Sunpower)
Estimated Annual Production: 2,781 KWH

Direction: East facing

Economics of Solar

I found this great article titled "Economics of Solar Electric Systems for Consumers: Payback and other Financial Tests" by Andy Black, July 2009. Mr. Black is a solar financial analyst and CEO of OnGrid.net.

If you are interested in gaining a more in-depth knowledge of why solar makes financial sense, I think this article does a great job. It's quite comprehensive and covers system performance, electric rates, incentives and financial returns.

If you want a quick snapshot approximation of what kind of returns/payback you can expect, refer to Figure 14 on page 15 in Mr. Black's article. There are various case examples for 12 states. For some states, there are high usage and low usage examples. The returns are much better for high electricity usage customers since they are paying big premiums for Tier 3-5 electric rates. I like the Lifecycle Payback Ratio - it's nice and simple and tells you how many times over in savings you can expect to receive for the cost of installing the system.

12 Weeks Solar Production

Our rolling 30-day average production is 281 KWH, which is higher than the target average of 228.6 KWH to achieve the CSI estimated annual production for our system.

Total After 12 Weeks:
Production: 694 KWH
CO2 Saved: 1,152 lbs
Estimated Savings: $138.80

System Size DC (STC): 2.28KW
System Size AC: 1.93KW
System Size AC (California CSI rating): 1.63KW
Panels: 10 Sunpower Serengeti 228 Watt
Inverter: 1 Sunpower 3000M (SMA Sunny Boy 3000 rebranded under Sunpower)
Estimated Annual Production: 2,781 KWH

Direction: East facing

Adding Solar Increases the Value of Your Home

According to the “Evidence of Rational Market Valuations for Home Energy Efficiency,” Rick Nevin, Christopher Bender, and Heather Gazan, Oct 1999, a home’s value is increased by $20,000 for every $1,000 reduction in annual operating costs from energy efficiency.

Using my home PV system for example, I expect to save approximately $550 per year on my electric bills. At 20:1, that would mean that I can expect to sell my house for $11,000 more now that I have solar. That's $3,600 more than what it cost me to install my PV system ($7,400 after the Federal ITC and rebates from my utility for my 2.28KW DC system). I'll get to reap the monthly savings while I live in my house and if I sell my home, I will get some, all or more of the cost back in the sale price.

11 Weeks Solar Production

This week we set another new daily production high of 12.99 KWH. Our rolling 30-day average production is 269 KWH, which is higher than the target average of 228.6 KWH to achieve the CSI estimated annual production for our system.

Total After 11 Weeks:
Production: 628 KWH
CO2 Saved: 1,042 lbs
Estimated Savings: $125.60

System Size DC (STC): 2.28KW
System Size AC: 1.93KW
System Size AC (California CSI rating): 1.63KW
Panels: 10 Sunpower Serengeti 228 Watt
Inverter: 1 Sunpower 3000M (SMA Sunny Boy 3000 rebranded under Sunpower)
Estimated Annual Production: 2,781 KWH

Direction: East facing

Electric Bill Savings Calculator

I made a quick Electric Bill Savings Calculator.  In general, for the models I have in this Blog, I designate the input cells in green shading, which is what you should change based on your personal information. Items shaded in yellow are key results or items.

Steps:

1. Enter KWH for each of the past 12 months from your electric bill into cells E9:E20 in the Calculator tab of the model.
2. Enter the estimated solar production KWH into cells E26:E37 in the Calculator tab of the model. Please refer to my post on Solar Home Buyer's Guide Part 2 to estimate your solar production.
3. Change the Region to your location in cell B4 in the Calculator tab of the model. This is based on my utility company Southern California Edison (SCE) - if you click to this link, there are PDFs of the region zones at the bottom of SCE's webpage.
4. If SCE is not your utility, you may need to tweak some items. Override the Tier Rates (cells F4:O4 on the Calculator tab) with your utility rates and tiers. You can either override the Baseline Daily KWH in column C on the Calculator tab or change the amounts in cells B24:C32 on the SCE Tiers tab at the end.

Results:

1. Average annual savings rate per KWH is shown in cell Q38 on the Calculator tab - highlighted in yellow.
2. Annual solar production as a percent of your total electricity usage is shown in cell E39 on the Calculator tab - highlighted in yellow.
3. Annual electricity bill savings as a percent of your total electricity bill without solar is shown in cell P39 on the Calculator tab - highlighted in yellow. You will notice that the $ savings % is higher than the production KWH % for solar. The reason for this is because you are offsetting the highest-priced electric rate tiers with your solar PV system and only paying your utility for the cheapest-priced tiers.
• The tiered pricing is very important in your financial returns. If you are a heavy electricity user (bills that are in Tier 3-5), you are paying hefty prices to your utility. The higher your electricity usage, the more financial sense it makes to go solar.
4. There are several graphical representations of your solar savings in the handful of charts I included in the model. Note that the text boxes in the charts need to be manually updated with the new totals you calculate if you want the charts to be accurate.

10 Weeks Solar Production

This week we set another new daily production high of 12.52 KWH. Our rolling 30-day average production is 263 KWH, which is higher than the target average of 228.6 KWH to achieve the CSI estimated annual production for our system.

Total After 10 Weeks:
Production: 555 KWH
CO2 Saved: 942 lbs
Estimated Savings: $111.00

System Size DC (STC): 2.28KW
System Size AC: 1.93KW
System Size AC (California CSI rating): 1.63KW
Panels: 10 Sunpower Serengeti 228 Watt
Inverter: 1 Sunpower 3000M (SMA Sunny Boy 3000 rebranded under Sunpower)
Estimated Annual Production: 2,781 KWH

Direction: East facing

New Solar Production High of Over 12 KWH

Amazing. We set another daily production high of 12.04 kilowatt hours on Wednesday. First time we broke 12 KWHs.