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

Some key production numbers

Total production up to 9 April 2021: 44138.39 kWh

Return on investment = 11.6 % per year; system paid for itself and gave 604.05 euro net income; net ROI 0.78 % per year.

• Production last day: 22.55 kWh = 5.16 kWh/kWp
• Production over last 7 days: 114.95 kWh
• Production over last 30 days: 455.99 kWh
• Production over last 365 days: 4923.28 kWh

• Daily production record: 31.40 kWh = 7.19 kWh/kWp (6 June 2015)
• Production record over 7 days: 205.77 kWh = 6.73 kWh/kWp/day (25 May 2020 - 31 May 2020)
• Production record over 30 days: 788.02 kWh = 6.01 kWh/kWp/day (4 May 2020 - 2 June 2020)
• Production record over 365 days: 5146.17 kWh = 3.23 kWh/kWp/day (3 June 2018 - 2 June 2019)
• Fastest 1000 kWh: 41 days = 5.61 kWh/kWp/day (18 June 2018 - 28 July 2018)

• Production minimum over 7 days: 7.23 kWh = 0.24 kWh/kWp/day (18 December 2012 - 24 December 2012)
• Production minimum over 30 days: 59.80 kWh = 0.46 kWh/kWp/day (5 December 2017 - 3 January 2018)
• Production minimum over 365 days: 4504.90 kWh = 2.82 kWh/kWp/day (17 April 2012 - 16 April 2013)
• Slowest 1000 kWh: 175 days = 1.30 kWh/kWp/day (23 September 2019 - 15 March 2020)

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 energy saving laundry dryer with heat pump. In 2020, we changed the heating of the house to include a 2kW/7.4kW heat pump system; we are curious how that will show up.

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

Since we have a meter with separate registration of produced electricity (a few weeks after installation of the system), we produced 43973 kWh. Of that, 10934 kWh (24 %) could immediately be used and 33039 kWh (75 %) was overproduction that has been delivered to the net. During the same period 27118 kWh (71 % of total usage of 38052 kWh) has been used from the net in darker hours.

The system is producing significantly more than we had expected, and our use was lower than the "average" predictions on our energy bill which we used to dimension our PV system. This made us a net producer of electricity for 8 years: until September 2020, we overproduced 9700 kWh. At that moment we bought a hybrid heat pump, so we will be using more. The total overproduction up to now is 5885 kWh.

Production by month in kWh

Production by month in % of cloudless model

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.
• 30 MWh was completed on 15 May 2018.
• 40 MWh was completed on 13 May 2020.
• On 1 July 2020, after 8 years and 5 months the system had completely paid for itself!
• On 31 August 2020 and 2 September 2020 we installed a hybrid heat pump; this winter we will be using the excess solar energy from the summer to heat the house.
• 2 September 2020 power was switched off for 45 minutes for the heat pump installation.
• 10 September 2020 we had a 35 minute power failure.
• 19 January 2021 the power supply to our panels and heat pump has been interrupted by the residual current device for 50 minutes before we noticed.

Comparing with other PV systems