Minneapolis Garage Goes Solar Power

When you think of a house that people were building in 1910, you probably don't think much of its ability to adapt to 21st-century infrastructure such as solar power. In the 20 years, I've lived in my old four square, I thought about it obsessively. But I always concluded that it wasn't structurally possible or economically possible to pursue these adaptations. In the past year, the planets finally fell into alignment when plummeting solar panel costs and the need to rebuild my garage combined. This allowed me to obtain a solar installation that promised to provide over 90 percent of my old home's electrical needs. I've come to realize that old houses can be surprisingly flexible with infrastructure adaptation. Also that owners should consider any renovation as an opportunity to update the home with green infrastructure such as solar power.

I'm not the first owner of my home to consider major retrofits to adapt to changing energy needs. After being initially heated by coal, the boiler was adapted for fuel oil and ultimately natural gas. This change was made possible with a gas line replacing a coal chute and an oil storage tank from the street. Considering this history, I began to see the house as an ever-evolving organism that adapts to changing times.

I've aspired to live in a solar-powered home since the 1980s, but when I purchased my first home, I got an assessment from a solar provider that was grim. I could only fit about 2-4 panels on my irregular roofline, powering only about 10% of our electrical needs. That put the payback on the project to almost 30 years – the expected life span of the panels. Discouraged but determined, I put the ambition on the back burner and continued to solicit bids every 3-5 years to see if it ever became economically feasible to do solar. Each contractor would say the same thing. Because of the gabled rooflines of both the house and garage, and with the extrusions of attic and sewer vents and skylights, there wasn't enough room to get enough panels on the roof. I'd probably have to wait until my next home to consider it.

My eureka moment came about two years ago when I realized my old one-car garage was about to collapse. It was probably constructed with a Model T in mind; it was poorly retrofitted to accommodate longer cars in the 1950s. Its compromised structural integrity made every trip into the garage one of fear of collapse. As the foundation and structural beams continued to deteriorate, I realized I couldn't wait any longer. But wait! I can design the new garage to make sure it can accommodate and maximize the use of solar panels!

The journey to getting solar up and running took almost a year. I needed to keep the plans for solar in every conversation related to the new garage – with the architect, the builder, and the city hall. The project's success came down to five key questions:

1. What Is the Solar Potential of the Site?

The garage site has a clear path to the sun at all times of year – an oasis of direct light in a historic neighborhood otherwise well-shaded by towering elms. Only a utility pole and its web of radiating lines would cast shade on the panels.

2. What Are the Design and City Code Issues with Solar Panels?

I worked with the architect to orient a broad expanse of south-facing, smooth roofs. Given the simple rule of thumb that when mounting panels, they should be at an angle equal to your geographic latitude, we aimed for a 45-degree roof pitch. City code dictated the pitch of the garage to be equal to the house, which is a 10:12 pitch, or about 40 degrees. Close enough. At this pitch, the panels would err on the side of slight over-performance during summer and under-performance during winter.

3. What Solar Panel Connectivity Concerns Are There?

With a detached garage, the placement of meters and other hardware got complicated. My electric utility required a new bi-directional meter that can turn backward when I generate more electricity than I can use. They also installed a solar production meter that calculates how many kilowatt-hours I produce so that they can pay me for the energy via their Solar Rewards rebate. We had to install a DC to AC inverter and emergency shut-offs at both the house and the garage. This caused us to dig a shallow trench to run the DC electricity from the garage roof to the constellation of meters on the side of the house. As unsexy as it is, this work amounts to a majority of the project cost and is required whether you put up one panel or (in my case) fourteen panels. So, economies of scale are pretty real with residential solar projects. 

4. How Best to Choose an Installer and Solar Panels?

After getting three bids, one installer stood out as being best suited for my project due to their extensive experience and level of comfort with small, residential jobs and their track record of being very attentive to customer concerns. When you deal with products of a 30-year life span, you want to buy a product from a company that will still be around in 30 years. I’ve watched two Minnesota-based solar manufacturers flourish. But then go out of business, leaving their customers without recourse, should their panels have any troubles. I chose to go with a Korean manufacturer that is a very diversified company and has less likelihood of going out of business during the lifetime of my panels.

5. What Are the Economics of Solar Panels?

In just over three months of use, the panels have generated 2.01-megawatt-hours of electricity. At Xcel’s rate of 11.9 cents per kilowatt-hour, that translates to about $240 of savings on utility bills, with the sun’s harshest months just ahead. At this rate, and from my initial analysis, I anticipate the electricity savings paying for the upfront investment in about six to seven years.

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At last!

The finished garage and the solar panels are operating as planned, proving that a new garage CAN be built to look consistent with the architecture of our historic neighborhood. It also abides by draconian building codes while creating an unobtrusive yet substantive solar array that one cannot see from any position on my lot. I love my 21st century 108-year-old home!