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Statistics for the PV installation on the roof of Rob, Anne and Maxim's house

Here is a list of accomplishments of our 4.37 kWp system that was installed on 27 January 2012.

Some key production numbers

Total production up to 19 August 2017: 27225.72 kWh

Return on investment = 10.1 % per year; 43.6% of value remaining to pay back (at 0% interest).

  • Production last day: 20.30 kWh = 4.64 kWh/kWp
  • Production over last 7 days: 115.04 kWh
  • Production over last 30 days: 550.10 kWh
  • Production over last 365 days: 4944.58 kWh
Positive records:
  • Daily production record: 31.40 kWh = 7.19 kWh/kWp (6 June 2015)
  • Production record over 7 days: 204.03 kWh = 6.67 kWh/kWp/day (2 June 2013 - 8 June 2013)
  • Production record over 30 days: 748.26 kWh = 5.71 kWh/kWp/day (20 May 2017 - 18 June 2017)
  • Production record over 365 days: 5066.59 kWh = 3.18 kWh/kWp/day (24 June 2016 - 23 June 2017)
  • Fastest 1000 kWh: 43 days = 5.32 kWh/kWp/day (6 May 2017 - 17 June 2017)
Negative records:
  • Production minimum over 7 days: 7.23 kWh = 0.24 kWh/kWp/day (18 December 2012 - 24 December 2012)
  • Production minimum over 30 days: 68.23 kWh = 0.52 kWh/kWp/day (12 December 2012 - 10 January 2013)
  • Production minimum over 365 days: 4504.90 kWh = 2.82 kWh/kWp/day (17 April 2012 - 16 April 2013)
  • Slowest 1000 kWh: 169 days = 1.35 kWh/kWp/day (7 October 2012 - 24 March 2013)

Graphs

The graph here below shows the production over the last 365 days. Each day of production is given as a black "o"-sign. The red line is the model calculation showing the expected production on a perfectly sunny day, at the average temperature expected for the season in our area. The green line is the running average 14 days before and after the day, averaged over all years the system has been installed.

You can see from this graph that in winter, many days are much lower than the "sunny" prediction, while in summer there are rare days where the actual production is lower than half of the model calculation. This can also be observed in the monthly average table below, where the percentage of the model prediction is shown.

The following graph shows what effect the production has on our family use of public electricity. The black line represents our usage of electricity (in kWh/day) one data point per year. You can see that we started saving significantly after we checked the use of all our electrical equipment in 2006, and eliminated a few huge consumers. From 2013 onwards we slowly replaced all lighting by LED. And in 2016 we bought a new laundry dryer with heat pump.

Starting 2012 a green line is added that shows our own production.

Since our new meter was installed, we produced 27060 kWh. Of that, 6436 kWh (23 %) could immediately be used and 20624 kWh (76 %) was overproduction that has been delivered to the net. During the same period 14348 kWh (69 % of total usage of 20784 kWh) has been used from the net in darker hours.

The system is producing significantly more than we had expected so far, and our use is lower than the "average" predictions on our energy bill which we used to dimension our PV system. This makes us a net producer of electricity: 6240 kWh were overproduced thusfar. Unfortunately, since January 2016 the surplus is only paying us 11 cents per kWh, which means payback time for our investment will be significantly longer than we thought.

Production by month in kWh

Month2012
(kWh)
2013
(kWh)
2014
(kWh)
2015
(kWh)
2016
(kWh)
2017
(kWh)
Jan26145107119119161
Feb250209224270246158
Mar418364502411439445
Apr501560520637569616
May621550623681647655
Jun572619674661556652
Jul585664606608671608
Aug601587551554628336
Sep476389423406479
Oct260263254291324
Nov13197153123146
Dec761258397105
All Year451745724720485849283632
2012
(kWh/kWp)
2013
(kWh/kWp)
2014
(kWh/kWp)
2015
(kWh/kWp)
2016
(kWh/kWp)
2017
(kWh/kWp)
All Year1033.51046.21080.01111.61127.8831.0

Production by month in % of cloudless model

Month2012
(%)
2013
(%)
2014
(%)
2015
(%)
2016
(%)
2017
(%)
Jan44.436.927.430.330.640.8
Feb47.441.044.053.146.630.9
Mar54.947.966.354.457.758.6
Apr57.864.760.173.865.671.1
May66.659.066.873.169.470.2
Jun63.768.975.073.561.972.6
Jul64.673.366.967.174.167.2
Aug69.968.364.164.473.162.9
Sep65.153.157.655.165.5
Oct43.944.342.748.854.7
Nov32.023.637.129.935.7
Dec22.837.524.928.931.5

Round numbers

  • Our first megawatt-hour (1 MWh = 1000kWh) was reached on April 19, 2012 at 8:15; 82 days and a few hours after installation of the system.
  • 2 MWh was achieved on June 11, 2012 during a very dark afternoon thunderstorm; that is 53 and a half days later.
  • 1 MWh/kWp (4370 kWh) was reached in the morning of a nice autumn day, 14 November 2012; after 291 days of operation.
  • 1000 Euro production was reached mid-day on 4 February 2013; a year and six days after startup.
  • 5 MWh happened early in the morning on "pi day", March 14, 2013. It took almost 168 dark days for the fifth MWh.
  • 2 MWh/kWp (8740 kWh) on 14 October 2013.
  • 2000 Euro production was reached 6 February 2014
  • 10 MWh was accomplished 5 April 2014, just before 18:00.
  • Until 24 October 2014 we have delivered a total 10 MWh to the power grid. Long live net metering!
  • On 27 December 2014 a nasty (incomplete) snow cover gave us "instable operation" and no power at all.
  • On the morning of 29 April 2016 we reached 20 MWh total production.
  • On 8 July 2017 at 13:00 we pushed the 20000th kWh into the net.

Comparing with other PV systems

To compare our production with other systems, check us out on SolarYield.EU. Numbers from our system there are entered by hand, so it may take a bit longer for them to be updated.