The Institute is Getting Solar Panels – Part I: System Design

We’re excited to announce that we’ll be installing solar panels at the institute this fall. While this has been in the long-term plans for some time, we have been prioritizing things that are more do-it-yourself, such as building solar hot water panels and gardening. In the LTI tradition, though, we’ll be doing as much of the installation as we can. You can stay tuned here at the blog for updates and also join us for a free weekend workshop when we do the installation. You can also thank the surprisingly quick occurrence of this project for the lack of blog posts over the last month.

Financing the Installation

We recently received a windfall, and we talked about various options for using this money well. Saving, investing, and other projects came up, but installing solar panels this year beat them all out for three main reasons. First, anything we can do that seriously reduces our use of fossil-fuel-derived energy is worth pursuing. Second, we live in the country and it is nice to have electricity back-up. Third, the federal governments’ tax incentives will be weakening over the next years.

By the numbers, we’re investing about $16,000 in the solar panel system. We’ll get 30 percent back in federal tax incentives ($4,800). Additionally, we can expect about 10 percent of the system cost back each year in energy savings ($1,600). That means the first year, we get a 40 percent return on our investment and a 10 percent return every year after that, even after the original investment is recouped. This is independent of stock market ups and downs or other economic shifts — the sun shines on regardless.

Note that the federal tax incentives are currently slated to drop by 5 percent every year into the future.

The System Design

As this project jumped up the line from our original plans, we hadn’t done as much background research before we dove into it. In our scramble to get our feet under us, we’ve found a few useful tools to help design solar panel systems.

One of the most robust (and finicky) tools was the National Renewable Energy Laboratory‘s System Advisor Model (download it here). This allows people to estimate the return on investment and performance of the system. Depending on a few parameters, we can expect to see between $800 and $1,100 in annual energy bill reductions. We started with SAM but really, it is best to use this tool once all the parameters are nailed down.


To get a better idea of the performance of different panels, configurations, and other settings, the SolarEdge design suite (available for free online) was the most user friendly we found. In it, the user specifies the location and other parameters, uses a satellite image to draw the roof space and shadow-casting obstructions, places solar panels, wires up the system, and simulates a year’s run. This makes it easy to see how a few tweaks of placement, panel selection, etc. can add up to more or less power. It was fairly intuitive if one has used Google SketchUp.

3-D model of site.
Optimal placement of panels.
Summary of energy generation.

The final tool we used was IronRidge’s design suite to create the rack system we need to hold up the panels. We have a lightly sloped roof and needed a custom rack to raise the panel angles up to meet our latitude (43°) as this is the optimal angle for energy generation throughout the year. Also, it will shed snow better with a steeper angle as opposed to mounting the panels parallel with the roof. We found this out through trials on the SolarEdge simulator. In the IronRidge simulator, we entered our system details, and it spit out a report about the size, type, and placement of rack components we’d need.

Rack details.
Mounting details.


Next week we’ll discuss more about the system and it’s components.

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