How low can it go?

Well, my latest PG&E bill hit my inbox this morning.  Since this bill covers the period when we switched from winter rates to summer, I was waiting to see how that impacted my results.  It looks like the results were very favorable.  The weather for the last 31 days has been pretty clear, and not too hot so that helped a lot.

The first 10 days of the latest bill covered the end of April, so it was still under winter rates.  For those 10 days, I used only 15 KWh at part peak, and 153 KWh at off peak.  Solar generation was 283.44 KWh, so my total utilization was just about 45 KWh a day.  The cost for this was a whopping $17.36.  A savings of $48 due to solar.

The final 21 days of the bill were at the summer rates.  The main difference in summer rates is that the day is now broken into 3 rate periods, with the addition of peak.  Peak rates are ridiculously high.  And part peak rates are not much better.  During the winter, the difference between part peak and off peak rates is less than 2 cents a KWh.  For the summer, part peak is nearly 2x off peak rates, and peak is 3x off peak.

This actually turned out to be a good thing for me.  The panels actually generated 18 MORE peak KWh of power then I used.  So, PG&E gave me a credit of just over $5 for this.  I only used 33 KWh of part peak power, and 320 KWh of off peak.  My total cost for the 21 days of summer power was only $31.90, for a total bill of $49.

Without solar, the total would have been just over $250, so savings were just over $200.   The medical allowance was much less a factor this month, as it saved me just a few pennies.  If I didn't have solar, it would have saved me about $60.  Time of use pricing also ended up saving me about $12.  It will be interesting to see what happens when it gets hotter, as I don't think my peak usage will continue to be negative.

Calculating savings

Now that I am a couple of months in, I am finding that PG&E does not make it easy to calculate the savings from.  I started trying to calculate savings using a simple spreadsheet, and found that it wasn't simple enough.  I then decided to write a quick program in C to do it for me.  It took only about an hour to have something that was usable and accurate.  Then I tried to share it with a few friends.  Microsoft apparently doesn't make it easy to just share a program, you need to pack up various pieces to make it work.  This got me to thinking there had to be a better way.  So, I started poking around, and found that it was possible to do it as a webpage.  Unfortunately, making a webpage to do the calculations involved learning Javascript, which was a bit frustrating.  After a few days, I managed to get a slightly less featured program to work.  It doesn't allow for easily modifying the rates, but I can add that eventually if I need it.  Otherwise, it has the functionality of the program I wrote in C.  In fact, it has the same basic algorithm.  I just wish I knew of a better way to debug javascript.  Not being a compiled language, I didn't have a compiler to help spot typo's, which was very annoying.  Anyway, I have it done, and if you are interested in trying it out, click here to give it a try.  I would appreciate any feedback or questions.

April Data

Since April is now in the books, it is time to look back at how the solar system fared vs what was projected.  Total generation for April was 744 KWh.  The finance company projections show that expected generation was 794 KWh.  So, 50 KWh short of expected.  This is 100 KWh closer to expected then March, but still short.  Projections for May are 930 KWh.  We will see how it goes.

Wow!

Month 2 results are in.  My April PG&E bill arrived in my inbox today.  And boy, is it a shocker.  My total bill for the last 30 days was $98.81.  This is the lowest bill I have ever received from PG&E.  Not all of the savings was due to solar, the wonderful weather we had helped quite a bit.  Without solar, my bill for this past month would have been $181 or so, by my calculations.  So, solar saved me $82 and change.  However, had my 1 year of free solar been up, I would have had to pay $140 for the solar power, resulting in a net loss for the solar of $58.

That is only telling part of the story though.  In pulling the numbers together for last months analysis, I found out that PG&E offered a medical equipment baseline allowance.  Since my wife uses a CPAP machine for her sleep apnea, we were able to qualify for that.  This increased my baseline allowance from 28.6 KWh per day to 35 KWh per day.  This saved my an additional $1.32 on my bill, after the solar.  But, if I didn't have solar, the medical allowance would have saved me $84.92.  Too bad I didn't know about this 4 years ago when we first got the CPAP machine!

Without the medical allowance, and without solar, my total bill would have been $265.94.  My savings would have been $165.81.  Even after paying for the solar, this would have left a $25.81 savings.  The chart below shows my projections of what the costs would have been in the various scenarios.

Solar	Med	Cost	Overall Savings	Solar Savings
Y	Y	$98.81	$167.13	$82.21
Y	N	$100.13	$165.81
N	Y	$181.02	$84.92
N	N	$265.94

March summary

In Cameron Park, we didn't have much of a winter to speak of. Until I got my solar panels installed, that is. Of the 31 days in March, I had 6 days with terrible (<5 KWh) generation, 4 days with bad (<10 KWh) generation, and 11 days with excellent (>25 KWh production), and 2 days of good (>20 KWh) production. The remaining 8 days were somewhere between 10 and 20 KWh. That left me with total generation of 503.4 KWh in March. This is significantly lower than the 655 KWh that the website shows me is the estimated production for the system. Hopefully, April is better for me!

TOU impact

I decided to do one more check. When they switched my meter, they switched me to TOU (time of use) pricing, rather than the fixed pricing I was on before. Turns out, this was a big help. I saved an additional $35 on this plan over what I would have saved had I stuck to the fixed pricing.

First bill

I received my first PG&E bill since installing the solar this week. Unfortunately, PG&E assumes when you go to solar, you don't want to do any analysis, so they send you a simplified bill. The bill didn't have the details I was looking for in order to see what my savings are. I called up the solar customer service at PG&E (the normal customer service is no longer able to help me) and found that the information I wanted was on page 4 of the bill, and they normal only send pages 1 and 2. They were able to flag my account to receive the detail bill from now on though.

Now that I have the full bill, I am able to see that I used 1389 KWh of power from PG&E for the 27 days that the bill covered. My solar system generated just over 547 KWh of power for the same period, putting total usage at 1936 KWh. Unfortunately, on March 1, PG&E changed rates further complicating the cost analysis, but with some help from Excel, I was able to do some calculations.

First, the big positive is that I stayed in the Tier 3 pricing, using less than 200% of baseline. This kept me from paying for the highest cost power. Without the solar, I would have been well into Tier 4 pricing. Each KWh in Tier 4 is 4 cents more than in Tier 3 (and Tier 3 is more than double Tier 2 pricing, adding 15 cents per KWh to the price). In order to calculate my savings, I added the solar generation to the appropriate tiers. My Tier 4 usage alone would have cost ~$128, but solar was able to completely eliminate that. I was able to reduce Tier 3 usage by another ~$45, putting the total savings for the month at $173.

These numbers are approximate, since I am unable to figure out how much of the power I used from solar was used during the partial peak prices (1-7pm weekdays) vs off-peak (all other times). PG&E allocates baselines based on % of power used at each of the rate periods (I used about 10% of my power during the partial peak period, so my baseline quantity for partial peak pricing was 2.86 KWh a day, rather than the 7 KWh a day it would have been had they done it based on % of the day spent in each rate category). Therefore, I made the assumption that all of the solar would have been used during the more expensive Partial Peak time-frame, rather than the cheaper off peak. This means my saving estimate is probably a little high, but the best I could do.

I did run the numbers, and found that the way PG&E does the allocation of the baseline actually works out in my favor this month, since I would not have used enough power to hit the full Tier 2 limits had the allocation been done on a percentage of time basis, so I would have had more Tier 3 usage in off-peak. The savings was right around $5.

Bottom line, the solar system saved me from paying PG&E around $173 this month, and cost my $0, since my first year of solar power is free. If I was paying for the solar power, it would have cost around $120, putting my net savings this month at $53.