
The solar industry in the U.S. is booming. Installations in 2023 increased 51% over the previous year, including more than 750,000 residential rooftop solar projects eligible for federal tax credits. The technology has blossomed to the point that even those in the biggest oil-producing state have embraced the power of the sun.
As a builder, I used to have a hands-off approach to solar. I focused on building a solid roof that could support panels and sometimes installed conduit for future photovoltaic (PV) wiring. I left it up to the homeowner to pursue renewable energy options with the expertise of a licensed solar provider.
However, aspiring to a net-zero standard of home performance, my partners and I realized this approach was shortsighted for several reasons, especially with new construction. Roof design and building orientation can have a tremendous impact on solar production. For example, removing (or moving) a single dormer may significantly increase the size and function of a PV array. Incorporating solar path analyses, which trace seasonal sunlight exposure over a proposed site plan, into the design phase can also be particularly helpful for maximizing renewable energy production.
Yet, even when decisions such as roof design and house orientation are beyond the builder’s control, as was the case with our Queen of Zero project in Maryland, there are still many advantages for taking a hands-on approach to the design and implementation of a solar energy plan.
Modeling the Queen
One of the first steps in designing a solar system for a new build is to estimate the home’s annual energy consumption. This calculation of electricity demand in kilowatt hours can be helpful in determining the appropriate size of a solar array and estimating the payback period associated with using site-based renewable energy. The model calculates energy demand based on characteristics of the home (size, geographic zone, orientation, wall system R-values, etc.), as well as the specifications for HVAC and water heating equipment, appliances, windows and doors.
With the exception of two direct-vent fireplaces, the 4,600-square-foot Queen of Zero single-family home operates entirely on electricity. Based off the home’s plans and specifications, Kelly Gillespie of Kelly Green Energy Raters estimated the Queen’s annual energy needs at 11,655 kilowatt hours (kWh) per year using a HERS (Home Energy Rating System) model via Ekotrope software. Because of the tight envelope and “beyond code” building materials, the HERS estimate was about 35% below the expected energy use of a code-built new home of similar size.
The Queen’s Energy – Solar System Specs
Early in the design process, our team determined that solar panels would not be a good option for this new Queen Anne Victorian-style home. In addition to panels looking somewhat odd on a turn-of-the-century design in a historical neighborhood, we also had the challenge of limited space for panel placement due to the amalgamation of hips, valleys, and dormers presenting no less than seven different roof pitches on the Queen (see image, below).

For this project, solar shingles offered a better alternative to panels – both in terms of aesthetics and potential energy production. There are multiple PV shingles on the market today, but only one product, the Tesla Solar Roof, evokes the look of slate material used on historic homes. Furthermore, the active (that is, wired photovoltaics) and inactive tiles of the Tesla roof blend together seamlessly, appearing as one consistent material. Most solar panels yield more energy per square foot than a typical solar shingle. However, at the Queen of Zero project, the full array of solar shingles proved more effective because the shingle is smaller, and installers could fit more units within the county’s rooftop PV setback requirements. The Queen’s roof supported 172 active solar shingles for a total 12.3kW system size (see image, below).

Yet, the Tesla Solar Roof does come with an substantial upcharge in material and labor cost, even when factoring in the Residential Clean Energy federal tax credit. When compared with a roughly 12.3kW system of solar panels installed over architectural asphalt shingles, I estimated a 2.5x upfront cost increase for solar shingles. American Home Contractors, the installer of our solar roof, offers a free instant virtual estimator for comparing the costs of panels versus shingles on its website.
Venting the Roof
To align with manufacturer recommendations, our contractor suggested that the Tesla Solar Roof be installed with ventilation on the underside of the roof sheathing. In a typical older home with an unconditioned attic space that includes soffit and ridge vents, a continuous stream of fresh air from top plate to tip of roof helps cool the roof’s surface and reduce condensation during hot, humid months. This natural air flow can lengthen the life of the roofing materials.
However, guidelines for Zero Energy Ready Home certification require all HVAC equipment to be housed within the building’s conditioned envelope. The Queen of Zero was designed with a fully insulated, unvented third-floor attic that included two bedrooms and a guest bath. Air handlers for the second and third floors were tucked behind knee walls, which were also fully insulated.
To meet the recommendation for natural ventilation, the Queen’s design team had to devise a strategy that would allow air movement despite the complicated geometry of the four-sided hip roof structure. We used ¾-inch purlins between the roof plywood and the trusses to create a pathway for air to reach the ridges. Next, we installed 1-inch sturdy baffles on top of the purlins (see photos, below). We covered the baffles with spray foam to air-stop and insulate the attic. The result is a vented air channel over an unvented attic space.


Backup Batteries and Smart Panel
The Queen’s renewable energy system includes two Tesla Powerwall backup batteries, each storing 13.5kWh of power. The batteries extend the benefits of the solar roof. During the day, when sunlight is plentiful, the backup batteries fill up on excess solar power. At night when the sun goes down, the battery power can be used rather than pulling from the grid. This system not only reduces utility costs but also helps support a more sustainable and stable electric grid.

The Queen’s renewable system is also designed to draw energy from the backup batteries in the event of a power outage. It may seem counterintuitive but, typically, interconnected rooftop solar systems do not function during an emergency outage—even if the sun is shining. The electric utility must shut down PV arrays to prevent dangerous electric currents on the grid. However, the Tesla system includes a gateway controller that permits the solar shingles to continue working by feeding power to the batteries. Tesla Powerwalls have a “stormwatch” mode that monitors the weather and will fill up, as needed, in advance of inclement weather.
According to Nick Zavala, president of American Home Contractors, the Queen’s backup system is designed for “energy independence.” In a total blackout without solar support, the batteries can maintain essential functions in the house for up to three days. Given a minimal amount of sunshine and a protocol for priority circuits, the “system can continue to work in perpetuity.”
To help manage energy loads and priority circuits for the battery system, we installed a 200-amp Span smart electric panel. The Span panel technology integrates seamlessly with the Tesla Solar Roof and Powerwall system to communicate which electric circuits will maintain power during an emergency. The Span has a user-friendly app that helps the Queen’s homeowner monitor electricity consumption for each appliance, equipment, fixture, etc. that's wired to the panel (see screenshots from the app, below), and the Span can be programmed to load-shed when needed to save energy.
Million-Dollar Question
From an energy efficiency perspective, the Queen of Zero appears to be set up for success. However, it will be several months post-occupancy before we know if the house will meet its net-zero goal (that is, a home that produces as much energy as it consumes over the course of a year). Energy needs fluctuate based on seasonal heating and cooling demands, while solar output varies based on sunlight exposure. In addition, occupant behavior can have a tremendous impact on the energy consumption of a home.
Based on the Queen’s energy model, we anticipate at least 85% offset of electricity consumption by the solar power system. However, the current version of Ekotrope does not account for the benefits of battery backups, so we expect that number to increase (look for a new version of Ekotrope in 2025 with storage variables in the model). Fortunately, the electric utility in our area offers “net metering,” which means that if the Queen produces more energy than she needs, the excess will be pushed out to the grid. At the end of the year, if the excesses exceed the grid consumption, the Queen could receive a refund check from the power company.
All photos by the author except where noted.