Charting out the Generation, Revenue, Expense of our PV System

I've cumulatively plotted out the revenue my PV system has generated over time as well as what I've paid on our load. I've also plotted out the microFIT payments I've received from Guelph Hydro. Note the following:

• revenue (blue) increases relatively over the spring and summer months and slows down over the winter
• our revenue was initaially greater than out payments, then over the first winter revenue was lower than the payments. The revenue overtook the loan payments in June 2011 and has been a net income ever since
• our net earnings to date have been approximately $8500-$7500=$1000
• the microFIT payments are lagging my loan payments - I've needed to keep a float in my account to cover the delay of payments
• the time period between microFIT payments from Guelph Hydro is rather variable. The last payment in particular was delayed quite a bit and I had to put extra money in my account to cover the automatic withdrawal of the loan payments. Guelph Hydro told me they are implementing a new billing and payment system that will automate their payments. They told me they had now over 100 microFIT contracts connected in Guelph. It also tells me that Guelph Hydro is much more consistent in sending bills to me than wanting to pay me.

Revenue generated, loan expenses, and microFIT payments

March 2012 Power Yield and How RETScreen is Doing

I've downloaded the data up to 13 April and I've put it in my spreadsheet to calculate the power yield for March 2012 (table below). It was marginally better than 2011. I am looking forward to the rest of April because so far the bright, cool days have been good energy producers. March 2012 was just 9 kWhr over last year. However, RETScreen calculations show that my system should have yielded 584 kW, so, two years in a row RETScreen is overestimating the system. Two years of data is not enough to say RETScreen is not accurate, but the overall trend with my system is underestimation. RETScreen calculated that my system should have produced 9128 kWhr to the end of March whereas my system did 8256 kWhr (10.6% under estimation). Most of the deviation came from the winter of 2010-2011 where snow substantially reduced the panel output. So, with this limited dataset, it points to people being conservative when estimating their payback expectations.

Sum - Daily kWhr	Years
Date	2010	2011	2012	Total Result
Jan		169.7	255.8	425.5
Feb		275.0	322.5	597.5
Mar		560.8	569.3	1130.1
Apr		492.9	313.5	806.4
May		534.3		534.3
Jun		707.2		707.2
Jul		769.0		769.0
Aug	164.0	658.5		822.5
Sep	438.0	528.0		966.0
Oct	450.0	391.1		841.1
Nov	355.4	316.3		671.7
Dec	78.2	219.8		298.1
Total Result	1485.62	5622.72	1461.16	8569.52

July 2011 PV Revenue Results

In my previous post I show that all but one day had very high PV generation for our system over July 2011. I don't complain about the one lower output day as we desperately needed the rain. On the 20 June 2011 we broke even since the winter where our cumulative revenue exceeded our cumulative loan payments. We had a very sunny June and we continued to add to our surplus so that by 1 July we started the month with $58.60 surplus. Don't forget, this is a surplus on a PV system that was over $31,000 and we had less than 2 more months to earn a little on our investment.
July was a very good month, adding to June's very strong output [and therefore revenue]. My chart below shows the cumulative revenue, loan payments, and microFIT payments we received.

Cumulative revenue, microFIT payments, and loan payments to 31 July 2011, 4.9 kW PV system.

We see the following:

• Revenue has exceeded loan payments by $341 by the end of July
• Return to date is 1.08% [profit over loan value]
• microFIT payments are a little irregular [number of days for each payment has been 49, 70, 68, 43, and 63]. I suspect that microFIT payments are manually processed at Guelph Hydro with "flexible" schedule
• Slope of cumulative revenue is greater during May-July vs. Aug-Nov [clearly showing the tendency of longer days in the summer, less cloud cover]. This trend should continue for the rest of the summer given the long range forecasts, though some rain is forecasted over next 2 weeks. 

I did do a boo-boo in some previous charts. I was showing earlier versions of the figure above with the microFIT payments including HST. The payments from Guelph Hydro includes HST. I must submit this to Revenue Canada so I incorrectly was including that tax as part of my revenue. The chart above is corrected and does not include HST. I shall talk about taxes in a forthcoming blog post.

May 2011 Cumulative

December and January could be a bad memory when you have grid-tied solar panels. But you need to have the long-term view. Even with the dreary May weather, the microFIT program is working out. At this point it is still too early to say what the ideal price is to achieve a reasonable return on investment. We are roughly 3/4 through the year and we are nearly equal to our loan payment [10 yr amortization]. However we are going into the long summer days and will more than exceed the loan. But that is only reasonable - many businesses require a 3 year return on investment so why shouldn't a homeowner have their own small solar business on their roof and get 7-10 year return on investment?
I show the cumulative revenue below.

The blue revenue curve is the daily generation from 24 August 2010 to 3 June 2011. I've discussed the low generation in earlier posts, but here we see there are enough sunny days that we are catching up to the cumulative loan. The net revenue was higher from August to December where it dropped below the loan payment. However, we now how enough data to see the growth in revenue that started in February has allowed the system to virtually catch up to the cumulative loan payments. On 3 June loan payments was $3043 and generated power was $2900. However, we should be expecting a cheque from Guelph Hydro soon - payments received to date have been $1762.

May 2011 Daily Results

It has been wet, cloudy, and not very bright in Guelph since mid-April. Not so great for solar or the farmers. We need the rain to keep the dust off the panels and to help the crops grow, but not this much!
The daily solar data is shown in the figure below. I cheated a bit - the first couple of days of June have been so sunny that I had to download the data off my Fronius datalogger to see how many kWhr we generated. I get wo pleased to the see the sun on the panels and the Fronius inverter purring away in the garage. These data are included in the daily results to date. The beginning and end of May had several days where generation was 20 kWhrs. Despite the intermittent cloud, the generation has been quite good on sunny days. My observations:

• 1, 2, 3 June 2011 - 33.5, 32.9, 32.4 kWhr respectively are the about equal to a few days in early May
• 1 June is 15 hrs 11 min 9 long whereas 1 May is 14 hrs 19 min long! Of course sky clarity is not equal between these dates and can be a notable factor
• 15 April is only 13 hr 25 min long and we generated 35.1kWhr, and 24 March is only hr min long yet 35.0 kWhr was generated
• Despite the cloudy days, overall generation has been fair to very good, meaning we are catching up nicely from the winter generation drop
• May generated 534 kWhr, or $428. This is a little below my RETScreen.net model which predicted 667kWhr in May for our system. This makes sense as May 2011 was generally recognized as much cloudier and rainy than normal.

Now, the important thing is to see the revenue generation that is resulting from the chart above. The chart below shows the daily revenue plus the daily loan equivalent [I pay loan biweekly].

There are indeed many days in May that are below the $10.70 daily loan equivalent, but whew!, it sure isn't December again!. Maximum daily generation in May was $26.83, the minimum was $2.98, avg $13.82.

April 2011 Revenue and Cost Results

The chart below shows an update of our daily revenue and loan. The horizontal line at $10.70 is our loan payment [we pay biweekly]. The individual points are the daily revenue [we get paid by Guelph Hydro bi-monthly].
My observations for April, or at least to 28 April, shows several things :

• a large scatter above and below our loan payment line, but the days where it is below $10,70 is not so dismally low as December and January
• the brightest day of April was the 15th which rivals the bright days in March. Even though the panels would have been a little warmer than in March, and the reflectance from the ground lower since the snow has melted, perhaps it is the longer day and higher sun that yielded more energy
• late April has been very cloudy and dismal here in Guelph, so revenue is on average lower than our costs
• final observation is that Chris Duke looks out his office window in April a lot and wishes for sunnier days. This has been wetter and cloudier April then other years [even the amount of fields with the corn sown is behind normal years]

April 2011 Generation Results

The bright sunny days of March have led to rather dreary days of April. This has been very interesting results for our solar power generation. I don't think there was one day in April of totally bright cloud-free days, though I'll check that later. In the mean time I am posting my PV generation to date. Given that the next few days that end April will be very cloudy and wet, I don't expect anything interesting, so I post this a few days before then end of April.
However, a quick note about extremely windy days today and yesterday. There was unconfirmed tornadoes in Kitchener, 20 km to the west of us yesterday, and very strong gusts here in Guelph. Our panels are still on the roof - that's a good thing. I was very impressed that our solar system installer [Merlyn Power]  called this morning to see if we still had panels on our roof or if there was any damage. Very considerate and consciousness of him.
So, the results:

• the middle of March was spectacularly bright as you see in my 03 April post. This continued into early April but mid to end of April were relatively cloudy with lower kWhrs
• 20 April was only 5 kWhrs which was a very rainy and dark day
• cloudy with sunny periods was yielding about 15 kWhrs

 

Snow sliding off solar panels and roof characteristics

I posted a photo of the snow having slid off the solar panels. We are fortunate to have a steep pitch to our roof and panels that aides snow sliding off. However, panels at the top right of the array do not have panels below them and have snow on the shingles blocking this snow from sliding. Note how snow has started to slide but has stopped [far right panels at top]. Much of the snow has slid off the panels to the left. The lower photo shows how far the snow can slide and be thrown away from the roof.
Though it is difficult to quantify, it seems that both mild and cold snow conditions result in snow sliding. Freeze-thaw cycles during the night and day can cause icing at the snow-glass interface and increase sliding resistance and physical binding of the snow to the panels.
Notice the relatively deeper snow on the lower roof of both houses. The combination of the lower pitch and the snow accumulation on the more sheltered lower rooves is quite evident. The snow on the lower roof is over 30 cm deep in spots. This would not be an ideal location for solar PV panels for good winter generation. The snow storm had wind blowing from the NW and has dumped snow on these SE facing rooves.

Guelph Solar Blog

I wish to share my experience deciding to install a solar photovoltaic system on our house in Guelph, Ontario. We are contracted to sell our power through the Ontario Power Authority's microFIT program. We are now receiving $0.802/kWhr.

I will post why I decided to do this project, how I proceeded, and how it is working out. I will try to post information here that I think will be useful for others who wish to do solar PV, for people who want to learn more about it, and to hopefully encourage further development of solar PV in Guelph [and beyond].

Full disclosure: I am not a vendor of solar equipment or services. I will not be taking any money from anyone related to solar, etc. I am fully independent. I do work for the provincial government working in renewable energy, but not solar. I am approaching this as non-work related. I will avoid any opinion, just the facts [positive and negative]. I will disclose any conflicts of interest.
Despite a similar name, this blog is not associated in any way with SolarG nor Solar Guelph.