Statistics for the PV installation on the roof of Rob, Anne and Maxim's houseHere 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 22 June 2018: 30761.65 kWh
Return on investment = 10.1 % per year; 35.1% of value remaining to pay back (at 0% interest).
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 we have a meter with separate registration of produced electricity (a few weeks after installation of the system), we produced 30596 kWh. Of that, 8773 kWh (28 %) could immediately be used and 21823 kWh (71 %) was overproduction that has been delivered to the net. During the same period 16930 kWh (65 % of total usage of 25703 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: 4857 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
Production by month in % of cloudless model