Solar for New Home Builders & Contractors

California 2020 Solar Requirements for New Homes

As of January 1st, 2020, if you are building a new home in the state of California, installing solar panels is mandatory. This is part of the new 2019 Building Energy Efficiency Standards – Title 24. Title 24 is not new, but the 2019 standard has changed a lot from the 2016 standard that California has been enforcing for the last three years.

The good news about this is that solar will save new home owners money and having it installed while building the home saves a lot of hassle.

The big question is, how much solar do you need to install to meet the requirements? There is an answer to this question, but it is a different answer for every house. The required size of the solar power system is affected by many factors including the size of the house, the insulation to be used, the windows (type, number and location) to be installed, whether or not the solar will have batteries and too many other factors to list here. Builders can choose to use a host of energy efficiency, demand-response measures, thermal storage and battery storage technologies to reduce the required amount of solar by up to 40% or more.

There is a basic calculation for all low-rise residential buildings (Equation 150.1-C) in the 2019 Building Energy Efficiency Standards

kWpv = (CFA x A)/1000 + (NDwell x B)


CFA = Conditioned floor area = (enter your value in square feet)

NDwell = Number of dwelling units = (enter number of homes)

A = Adjustment factor from Climate Zone Table (below) =

B = Dwelling adjustment factor from Climate Zone Table (below) =

kwPV = kWdc size of the PV system = N/A (calculated once all values are filled)

The adjustment factors A and B from the table are based on the climate zone. There are also some exceptions to this equation based on building height, the addition of a battery storage system and effective annual solar access.

You can reduce the size of the required system with other energy efficiency improvements and then the calculations are far too complicated to be done by hand so computer software is required. Currently, there are two software programs that are approved by the state. They are CBECC-RES 2019.1.1 and EnergyPro Version 8.0. It is important to use the correct version of the software as the older versions will not comply with the new code.

These software programs are really the backbone of Title 24 compliance. Choose one and go through the training materials to learn how to use it. Basically, you will enter all the details of the home that relate to energy use and energy efficiency to come up with a comprehensive plan for building your house to meet the standards. In the software, you can do things like lessen the insulation in the walls and then see how much you have to upsize the solar to still be in compliance. If you want to install less solar, put in the smaller system and see what other aspects of the build you can tweak to stay in compliance.

Beyond this software and the text of the actual code, there are some 300+ page compliance manuals which would be great bedtime reading material if you have insomnia.

Finally, as the state points out in their FAQ document, this isn’t a completely rigid “mandate”. If solar really doesn’t make sense, there are exceptions to the requirement for specific circumstances like insufficient sunlight availability or locations where electric rates are uncommonly low. The Energy Commission may also approve community-shared solar options as an alternative to onsite PV systems. But don’t put off building thinking you can avoid the mandate. The overwhelming majority of new homes will have to have solar – and why fight installing something that will save homeowners money?

Build with Solar Once for a Lifetime of No Energy Bills

When building a new home, you have the opportunity to build it right from the get-go, saving yourself thousands of dollars in utility bills over the decades (as well as offsetting the associated fossil fuel emissions).

New construction does not need to be expensive to be sensible. The costs to improve a building’s insulation values and install solar equipment are quickly recouped by energy savings. Generally, high-efficiency new homes consist of the following properties:

  • Airtight, well-insulated building envelope allows you to save the precious BTUs generated by your heating system in winter or cooling in the summer.
  • High-efficiency appliancesmake the most of the energy they consume. Electricity is appealing because you can generate it for free with solar panels on your roof.
  • Renewable energy systemsoffset the energy you do need. A properly designed solar array and an all-electric house = freedom from utility bills, forever.
Solar array on a newly constructed home in Jackson, New Hampshire

We had discussions with the homeowner of this new construction project from early stages. Perfect solar orientation, a metal roof (great for solar!) and communication for prepping conduit runs saved the homeowner some costs and optimized the potential of the array.

Factors to Consider When Installing Solar on a New Home

While we think it makes the most sense to consider solar in the context of a new home that is also energy-efficient, we have plenty of experience integrating solar with conventionally built homes as well.

The primary factors to consider when installing solar for a new home:

  • South-facing roof– Probably the most important attribute for new construction is that a home be built with an adequate south-facing roof. The roof does not need to face perfect (195°) solar south, +/- 90 degrees is still viable for solar). A roof pitch between 5 – 12 is ideal. Lower sloped roofs bias towards summer production, higher roofs bias towards winter. Roof features such as dormers, vent pipes, chimneys, and other roof mounted utilities interrupt the roof-span and make it more difficult to install solar arrays.
  • Shade-free site– The south-facing roof space should be located in a shade-free area of the site. Ideally there will be a clear solar window from 9am-3pm, year round, to maximize solar performance.

    Shade-free site

  • Access to utility room– A solar array will require a pipe run and/or a wire run depending on system configuration. New construction is an ideal time to integrate pipe or wire runs within the home’s frame.
  • Obstructionssuch as vent pipes and chimneys should be avoided on the solar roof. If they are present they should be held towards the ridge and/or to one end of the roof. Place them as far away from south as possible.
  • Avoid dormerson the south-facing roof as much as possible.
  • Asphalt shingle and standing seam metal roofsare ideal choices when installing a solar system. Avoid metal shingles, cedar shingles, and exposed fastener metal roofs whenever possible.
  • As far aswiring is concerned, if you want to prep for solar but not install solar as part of the initial construction, most residential installs will need one run of 3/4″ conduit. If you have us install solar on your new building, this is part of our normal scope of work, but check with our designers for site-specific details. We can always retrofit but it’s certainly easier to put the pipe in while the walls are open.
  • Roof load– Generally speaking a code-built roof will be sufficient to carry the additional load of solar panels. There is the snow factor; a reasonably pitched roof sheds snow pretty readily.

Solar During the Building Process

We are happy to have introductory conversations throughout your process of identifying lots and determining what kind of home you would like to have built (we can also recommend some preferred builders and architects if you’d like). Where we usually start formally is when a client has a set of building plans and wants to talk in more detail about their desired mechanical systems and how solar will fit into their home design.

We work with many types of projects, from homeowner-contractors to homeowners who are working with a variety of professionals. Generally, it is helpful to have all stakeholders available during early meetings so that we can offer suggestions that save time, money, and effort over the course of your project.

We have worked on hundreds of new construction projects on some of the highest efficiency buildings in the region, and bring this expertise to every project that we are involved in. Our goal is for you to be blown away by your experience with solar, and professionalism at every step of the way is key to that happening.

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