Is electric baseboard heat powered by solar panels an efficient choice for our new addition?
Baseboard heating that can be zoned is often a good strategy to serve added floor area and avoid upgrades to an existing forced-air system. However, I would encourage you to consider alternatives to electric resistance heating.
While an electric resistance heating system imposes the lowest initial installation costs, it is typically the most expensive system to operate. Electricity "is the least efficient source of heat," according to the U.S. Department of Energy's EERE (Energy Efficiency and Renewable Energy) information center. Most electricity is produced at centralized power plants from fossil-fuel generators that convert only about 30 percent of fuel energy into electricity, after accounting for fuel extraction and transportation, generation, transmission, transformation, and end use. For this reason, I would not recommend electric resistance heat on a project larger than a very small addition to your home. As for solar panels, the main priority when defining the size and cost of a solar photovoltaic (PV) system is lowering your overall energy demand, and installing an electric resistance heating system would not achieve this.
A more affordable and more direct solution for you would be a solar thermal (hydronic) system, which can be used to supply both space heating and domestic hot water. In terms of initial investment, a solar thermal system would be significantly less expensive to install than a PV system tied to the grid.
The heating system may be baseboard mounted or integrated into the floor. Baseboard heating is more accessible than radiant-floor heating. It also doesn't have the potential to impact floor finishes, and takes only a few minutes to heat, whereas a radiant system can take longer to "charge." An advantage of radiant floors over baseboard heat is that there is less of an impact on furniture layout. A relatively high level of user comfort in warm-floor applications has made radiant systems increasingly popular, but relative efficiency, cost effectiveness and flexibility are debatable.
With a solar thermal (or a PV) system, it should be noted that backup heating in the form of conventional options—ranging from a central furnace to space heaters—will often be required. Typically, an active solar system designed to meet 100 percent of heating needs is not practical or cost effective. Also, building codes and mortgage lenders often mandate a back-up heating system.
Before committing to a rooftop solar system, local legal restrictions and permit requirements must be considered. Zoning regulations, including building height requirements and preservation of neighbors' access to sunlight; building-code regulations addressing issues like the structural capacity of a roof to support a solar installation; homeowners association covenants and other local restrictions may apply. Homeowners considering solar should also contact their home-insurance policy carrier to confirm coverage and exclusions.
For more information:
Here are three nearby companies whose work I know and trust: Colvin Mechanical in Half Moon Bay (email: colvinmechanical AT gmail DOT com), home performance consultant Tom Wagner who's based in Palo Alto, and Armor Construction & Design in Santa Cruz.