Low and zero emission homes require unique considerations for their electrical wiring and service design. Builders should prepare to accommodate electrical capacity to support electric vehicle readiness and solar readiness, as well as other LZE technologies. 

Electric Vehicle Readiness

Because electric vehicles are expected to replace traditional vehicles in coming decades and approximately 80% of EV charging happens at home, consumer demand for homes ready for or equipped with EV charging is growing. In EV-ready homes with private parking, a heavy-duty power outlet (usually 240 Volts) is wired and ready to support the installation of a Level 2 electric vehicle charger. There are two paths to making a home EV-ready: 

• Pre-install conduit: Designate enough space and capacity on the main electrical panel or garage subpanel for at least a 40-amp, 240V dedicated branch circuit. Install conduit linking the electrical panel to the future location of the EV charger, near where cars will be parked. 

• Wire a Level 2-ready outlet: In addition to the pre-wire steps, install a 240V grounded alternating current receptacle, allowing a homeowner to purchase a plug-in Level 2 EV charger without the extra wiring expense. EV chargers are available for a range of outlet types, including the popular NEMA 14-50. 

Builders wanting to go one step further can follow these steps by completing the installation of a Level 2 EV charger. 

Solar Readiness

Solar-ready homes are pre-wired with the electrical capacity and infrastructure to support the future installation of solar panels. Because solar panels offer a variety of financial and reliability benefits to homeowners and can increase the sale prices of homes, integrating solar PV-readiness into new construction is becoming more popular in the U.S. 

Sizing Electric Service

Sizing the electrical service and panel capacity for an all-electric home is pivotal during the construction process and saves homeowners from incurring costly expenses in the future. Upgrading the panel capacity at the time of installation can cost only a few hundred dollars whereas retrofitting it down the line can cost thousands. Most all-electric homes will require at least a 200-amp service to accommodate all-electric appliances, ultra-efficient HVAC equipment, and pre-wiring for electric vehicle charging and solar PV installation.  

With the use of smart management systems or smart planning, however, smaller electrical services can easily accommodate all-electric appliances and HVAC equipment. Peninsula Clean Energy found that across more than 100,000 single-family homes in their service territory, more than 80% of homes never pull more than 40 amps. Most homes do not use all of their energy-intensive appliances at once, making it possible to fully electrify a home using a 100-amp electrical service. 

Electric Wiring/Service Resources

• Building America Solutions Center’s Wiring Conduit for Solar PV Systems Guide 

• Zero Energy Ready Homes Solar-Ready Checklist 
  • The Zero Energy Ready Homes program’s Solar-Ready Checklist describes how a builder can meet the program’s PV-readiness requirements, and the conditions under which a home is exempt from meeting PV-ready requirements. 

• The National Renewable Energy Laboratory’s Solar Ready Buildings Planning Guide 

• The U.S. Environmental Protection Agency’s Solar Photovoltaic Specification, Checklist and Guide 

• ENERGY STAR’s Building Electric Vehicle-Ready Homes Factsheet 

• ENERGY STAR Product Finder – Electric Vehicle Chargers 
  • AC-Output Models 
  • DC-Output Models  

• National Electrical Code Article 220 Branch-Circuit, Feeder, and Service Calculations 
  • Provides the methods and requirements for calculating the load for branch circuits, feeders, and services.