Energy invoice 2015

This week I received my energy bill of 2015 and it turns out that it was a year with a lot of sunshine. The output of my solar panels was more than I expected. The graph of my provider displays my consumption of the recent years: The top graph shows the consumption of electricity. In 2014, our eldest son left our house and our second son moved the next year. So, the solar panels were not the only reason for the displayed savings in the graph, but the difference with the year 2009 is fantastic.

Our electricity consumption was 9,860 kWh for 2009. Our current electricity consumption from our provider is 1,756 kWh. So we managed to save more than 8,000 kWh and 8,000 kWh * $0.22 is a cut of $1,760, - per year! My solar panels generate 4,500 kWh per year, so the remaining savings of 3,500 kWh were because of other saving activities.

I have compared all the invoices of the last few years and just looking at the investment of the solar panels, then I will have recouped the investment within three years from now (from the start date within eight years).

The gas consumption (since the latest repair of our system) is now stable, but the investment in the hot water system is unfortunately disappointing. So, my advice is to buy solar panels first. Buying Solar Panels is really profitable. The payback period of a hot water system is longer and you have to be a little more patient. Solar panels are halved in price since 2010!

East-West setup solar panels

I recently heard the possibility of an arrangement in an East-West direction for solar panels. I was curious about the payback period and wanted to compare it with a traditional setup with the alignment to the sun.

I used the App Solar Consult (for iPhone/iPad) and entered the size of a flat roof. Although the output is 1% more at an angle of 10 degrees (in an East-West setup), I've entered in both cases an angle of 15 degrees. I entered in the app that we have a flat roof of 27 feet (the sunny side) at 20 feet (the other roof side).

Traditional setup of solar panels with a direction to the sun: 
First I calculated the optimal setup with the solar panels of Autarco. The result of the calculation was 2 rows of 8 solar panels (16 panels of 315 Wp per panel size 6.4 x 3.3 feet). This setup has a capacity of 5,040 Wp and on my location (in The Netherlands) the output was 91% relative to the power (Wp), so it was 4,571 kWh.

Calculation of an East-West setup of solar panels: 
If you choose in the App to calculate with an East-West setup, the result is 2 rows to the East and 2 rows to the West. In each row 6 panels fit next to each other and in that case the rows lie with their backs against each other (see the picture which displays an East-West setup).

4 rows of 6 panels is a total of 24 panels with a power of 315 Wp per panel. This setup has a capacity of 7,560 Wp (50% more then a setup to the sun) and the App Solar Consult calculated that this arrangement will give an output of 82% relative to the power (Wp), so it was 6,256 kWh (37% more).

Furthermore, solar panels are usually placed in two strings, wherein the output of the worst panel determines the output of all the panels in the string. In an East-West setup, you could place the panels Eastwards in one string and the panels towards the West in the other string.

In summary: 
It appears that the East-West setup the output per panel is (relative to the power) 10% less, but you can place more panels (24 instead of 16). This is only profitable if the payback period is the same or less. I helped my father to buy 13 of these solar panels and he paid $500 per panel on a flat roof (including the inverter, standards, mounting hardware, wiring, assembly, travel costs and additional group in the fuse box).

Payback time of solar panels with a direction to the sun: 
The more panels you let install the cheaper per panel, but how much is now required to make it profitable. I used the App Solar ROI (only for iPhone/iPad) to calculate the payback time. With this App, you can enter some variables to calculate the payback period of solar panels. I have entered 16 panels of $500 each and an output of 4,571 kWh, according to the App Solar ROI, the payback time was 7.9 years.

Payback time of solar panels in an East-West setup: 
I entered 24 solar panels of $500 each and an output of 6.256 kWh. The payback time was in an East West setup 8.7 years. If you enter 24 panels of $458 each (8% cheaper) and an output of 6,256 kWh, then the payback time is also 7.9 years (same result as in the first calculation).

Conclusion: 
In case of a flat roof you can place in an East-West setup 50% more solar panels and this results is 37% more kWh. The payback time is only shorter if the price is at least 8% per panel lower. If you buy 50% more solar panels then the price per solar panel should be lower, because:

• The travel expenses are only once and this will not be different if you order 50% more panels; 
• The work and time for mounting and installation of an inverter with more power, is the same; 
• The peak power of the inverter does not need to be 50% higher in an East-West setup. In the morning generates the Eastern side more electricity and in the afternoon the Western side; 
• Some suppliers have special standards for East-West setups and these are cheaper than traditional standards (less material). 

Advice: 
If you have a flat roof and want to generate as much electricity as possible, ask for an estimate for the traditional setup compared to 50% extra panels in an East-West setup. Divide the price by the number of panels and see if the price is at least 8% lower per panel.

My experience is that the investment of an offer from 16 to 24 panels is only 4% cheaper per panel and therefore the payback time will be five months longer. Still, my advice is to choose the East-West setup and accept the extra five months. Accordance the App Solar ROI, you will save annually $1,052 with 16 panels and $1,439 with 24 panels in an East-West setup (this is a difference of $387 extra per year). The App Solar ROI shows a result of $7,500 more profit for an East-West setup after 25 years.

Why a smaller angle for solar panels on a flat roof

If you want to install solar panels on a flat roof with an alignment to the sun, then the optimal angle in the Netherlands is 35 degrees. However, there are reasons to choose for a lower angle: The material (standards, assembly material and necessary ballast) at an angle of 15 degrees is a lot less (lower angle captures less wind) and the additional costs for an inclination of 35 degrees are the higher result not worth (2% more output). So, the payback period can be longer at an inclination of 35 degrees.

It should be avoided throughout the year that the rows of panels are not placed in each other's shadow (a shadow behind the row of solar panels in an angel of 15 degrees is less than an angle of 35 degrees). The optimal angle and shadow can be calculated with the App Solar Consult (iPhone/iPad only). The shadow of solar panels of 6.6 feet X 3.3 feet at an angle of 35 degrees is in the Netherlands 3.8 feet. The shadow is in case of an angle of 15 degrees not more then 1.7 feet during the winter. That's a big difference.

Furthermore, in case of an angle of 35 degrees, the solar panels need to be installed at a distance of 3.8 feet from the edges of the roof (depends per country). These three reasons should be balanced with knowledge of 2% loss of output.

My father (see one of my previous blogs) was aware of the differences, so he had deliberately chosen an angle of 15 degrees. The decisive argument for him was to see much less from the solar panels standing from the ground level. He has decided with good arguments and accepted the lost of 2% output.

Payback Time Solar Panels

The App Solar ROI is the first free independent tool that calculates the payback period of solar panels without commercial involvement. R.O.I. stands for the English term Return on Investment. ROI = Income per year / Investment

In Solar ROI you can compare offers and the higher the ROI, the sooner you have recouped your investment.

However, the payback in years depends on several factors. In a project, you should compare the result with the situation if you do nothing. If you would not buy solar panels, will you leave your money on saving account and receive savings or are you going to spend it on something else? In the first case, you may also face property tax. The results are displayed in a table or in a graph. The tool is not a black box and all calculations are displayed and explained in datasheets.

Decrease cost of solar panels

Today, there are solar panels installed on my father’s roof. He has a house with a flat roof and consumes about 3,800 kWh per year. To buy solar panels is a simple thing, but there is a lot of choice in the types of solar panels. Of course we asked for a several number of requests from various solar panel companies.

The App Solar Consult can calculate for you the output of solar panels. With this tool for comparing solar panels displays the optimal output of solar panels. Interestingly, the solar panels now looked a lot nicer then a few years ago and a lot of black panels are offered. The panels are also standard equipped with partitions so that the weather will not affect the setup.

My father has installed 13 black solar panels of 315 Wp on his roof and the cables are neatly concealed in plastic tubing. The reason for choosing this supplier was (in addition of the good price) that we have received a certificate after the installation. With this certificate, an output of 3,750 kWh per year was guaranteed and this will be checked after five years and after ten years (online). If the panels have less output than described in the certificate, the difference will be paid for $0.20 per kWh.

For this, the converter was connected to our network via WiFi and can be reached online via their website (after logging with his account) to see the revenue per day, per month and in the entire period after installation.

We have both installed a solar panel system on a flat roof. So we can compare the cost of the entire system (including the inverter, standards, mounting hardware, wiring, installation and additional group in the fuse box) after 5 years. So I have reference material to compare the prices of solar panels (with my personal experience), which are nearly halved since 2010:

With the App Solar ROI (only for iPhone/iPad), we calculated the payback period of solar panels and concluded that his investment was returned within seven years.

Compare solar panels

Installing solar panels in itself can be realized in a single afternoon, but to buy solar panels take more time. Suppliers and installers will give you an advice, but are more interested in promoting their own solar panels. Solar panels buying should therefore not be underestimated. However, there is an App available for the iPhone and iPad that can help you with comparing solar panels. This independent solar calculator compares the most sold solar panels:

The App Solar Consult shows whether your roof is suitable for the installation of solar panels and what is the optimal setup.

The orientation meter works like a compass that will display the deviation from the South (or North). You can put the phone on the roof or hold it against the ceiling. In addition, the inclination of the roof will be measured and the efficiency of a solar panel will be displayed relative to the optimal position.

If you are considering installing solar panels, the App can help you in your research whether your roof is suitable for solar panels. The App shows whether there falls enough sunlight on your roof and whether it is worth to install solar panels. You can enter an address or display your current location.

You can enter the details of your roof and the App will calculate for your roof with multiple types of solar panels the maximum output in the tab ‘Characteristics roof’.

Also, the required surface of solar panels on pitched and flat roofs are displayed. The App displays the length of the shadow behind a row of solar panels.

For more information see the App Store: Solar Consult.

Optimal angle solar panels

Last week I had a conversation with a neighbor why my panels are not installed at an angle of 35 degrees. This angle is the optimal angle for solar panels in the Netherlands.

The reason was that in case of an angle of 36 degrees, I was supposed to install each row of panels at a distance of 14.4 feet of each other. Otherwise, they would stand in each other's shadow (in the winter). I didn’t want more then 8.2 feet space for shadow and I wanted the rows of panels with no more than that distance from each other installed (otherwise I could not install18 solar panels on my roof).

In my case, we came up with an angle of approximately 20 degrees: According to the following image shows an inclination angle of 20 degrees to a loss of 4%. Since my panels were aligned to the South-East, there was already a small loss taken into account. The combination of South-East and 20 degrees still fits within the first circle of the diagram and gives only a loss of less than 5% output.

For the iPhone and iPad is the free App Solar Consult developed, which - depending on the size of the roof - the most optimal setup for solar panels on your roof will be calculated using most types of solar panels. In addition to the location of the rows and orientation of the solar panels (landscape or portrait), the angle of the solar panels will be calculated, so that the rows of solar panels will not be installed in each other's shadow in the winter.

The App Solar Consult gives the setup with the highest output as advice.