Producing our own electricity

Since 27 January 2012, we are producing our own electricity using a photovoltaic (PV) system on the roof. This is the story that goes with it.

The Difference Outside

Here are two pictures before the change. Note the little ventilation outlet at the left of the front roof (which was moved to the back), the birch tree which is a little too high, and the winter shadowing on the side roof which determined the configuration of the panels there.

Front roof - before Side roof with winter shadow

The front roof is pointing south-by-southwest, this should give 98% of the optimal power in The Netherlands. The side roof is slightly less efficient (88%), but picks up the sun in the early summer morning (there are many web sites where one can calculate these efficiencies).

Here is the situation just before sunset on 27 January:

Front roof with panels installed side roof with panels installed

The front has 18 Senersun panels (150x80 cm, 190 Wp each), configured as 2 strings of 9 connected to one channel of the inverter. The side roof has 5 panels connected to the second channel. Total power is 23x190 = 4370 Wp. At our location and with this configuration, this was predicted to produce 3950 kWh/year; approximately our own "regular" consumption according to our electricity company. After approximately ten months we can say that the production is far above the expectation, and that our electricity use is significantly below this "regular" number, so we are a net producer of electricity.

Indoor Equipment

In house, the inverter is mounted on the attic, connected to a 240V / 25A fuse in the mains cabinet (switched off on the picture at the right):

Mains cabinet: the new fuse

The display on the inverter shows the total power produced, the power produced today, and the current power. It also alternately shows the determined optimal V/A setting for the two channels.

The Power

We don't need to go to the attic to check on the status! A small solar-powered monitoring unit in the living room gives us a heads-up on the system.

5 minutes on! During the first full day After one day

The first picture is 5 minutes after power up on the day of the installation, the second picture is during the first full day, and the third picture is the result after one (winter) day of our own power: 6.7 kWh. This unit can also be connected to the computer via USB. This makes it possible to get historic readouts per 10 minutes. This results in our statistics pages, which compare the actual production with model calculations.

Now only 4000 more days needed to repay the investment!

The Timeline

To give an impression what is needed to install your own solar power in The Netherlands, this is our timeline. It may be nice to place this into contrast with the experience of Scientific American's George Musser .... From decision to execution in 103 days (plus some extra aftermath)

16 October 2011 Decision is made to place solar power on our roof. Some research on the web indicates that there is no government subsidy, that no special permit is needed to put the photovoltaics on the roof (within some limits) and that the electricity supplier is obliged to buy the produced electricity at normal tariffs (net metering, within reason). We ask a company at 1km from our house for an estimate what they think is necessary.
25 October 2011 We get a first offer with a rough indication that it may be possible to place 5040 Wp.
9 November 2011 After an e-mail discussion about the components, we give a basic OK.
11 November 2011 A visit from one of the people of the company, making actual measurements of the roof.
15 November 2011 A nice sunny day. I make pictures of the roof several times during the day to determine the shadowed parts. Pictures are mailed in.
16 November 2011 An adapted offer comes in, giving us a choice of either 4750 Wp or 4370 Wp.
25 November 2011 After some final deliberations and working out the details, the offer is signed and returned.
10 December 2011 We (ourselves) prepare the power supply from the meter cabinet to the attic, and prepare a mounting plate for the inverter.
19 December 2011 The ventilation channel is moved from the front to the back roof.
16 January 2012 All equipment has arrived. Appointment for installation is made.
20 January 2012 Gardener helps with winter cleaning, pruning the birch tree so that it can not throw a shadow on the roof.
27 January 2012 Installation.
30 January 2012 Called electricity company to tell them we have our own system.
30 January 2012 Expert from electricity company tells us it is better to install a digital power meter. We ask for an installation.
14 February 2012 Digital power meter installed. Unfortunately not a "smart" meter, because the gas and electricity meters are at more than 2 meters distance from each other.
20 October 2017 Smart power meter installed. We needed service because the day/night clock of the old installation needs to be reset anyway.
30 December 2017 We hear that a change of insight means we can anyway get reimbursed for the VAT for the installation.
20 July 2018 The VAT is returned on our account.