Solar Contractor License Exam Practice Test

Description

Sample Questions

Question 1. A homeowner wants a grid-connected solar PV system. The property has a partially shaded roof, and the homeowner plans to purchase an electric vehicle within the next two years. The contractor estimates the system size using only the homeowner’s most recent electric bill, which reflects unusually low consumption during a vacation period. What should the contractor do before finalizing the system design?

A. Size the system to offset the lowest recorded monthly consumption to prevent overproduction.

B. Use the roof’s maximum physical capacity as the primary sizing criterion, regardless of household demand.

C. Review a representative 12-month electricity-use history, assess shading and usable roof area, and account for the anticipated electric vehicle load.

D. Select the largest inverter that fits the electrical service and allow the utility to determine the appropriate array size.

Correct Answer: C. Review a representative 12-month electricity-use history, assess shading and usable roof area, and account for the anticipated electric vehicle load.

Answer Explanation:

A sound solar estimate begins with an accurate understanding of the customer’s energy requirements and the property’s physical limitations. Reviewing 12 months of utility consumption helps identify seasonal changes and avoids designing a system around an atypical billing period. The contractor must also evaluate roof orientation, shading, available installation area, structural suitability, and applicable permitting and utility requirements. An anticipated electric vehicle can materially change future electricity demand, so its expected charging load should be considered during system planning. The final design must reconcile energy objectives with equipment ratings, site conditions, applicable codes, and the customer’s budget. Neither maximum roof capacity nor a single unusually low bill provides a reliable basis for system sizing.

Why the Other Options Are Incorrect:

A. Size the system to offset the lowest recorded monthly consumption — Incorrect.

An unusually low month does not represent the household’s normal annual electricity demand. Using it can produce a system that is undersized for ordinary consumption.

B. Use maximum roof capacity as the primary criterion — Incorrect.

A roof may accommodate more modules than the customer needs or the electrical system can support. Roof capacity alone does not establish appropriate system size.

D. Select the largest inverter and let the utility determine array size — Incorrect.

Inverter selection requires electrical design calculations and compatibility checks. The utility does not ordinarily determine the customer’s complete PV array design.

Quick Study Guide:

Start residential solar planning with historical electricity consumption and the customer’s future energy needs. Assess roof orientation, shading, structural condition, usable area, and electrical service capacity. Estimate system production using appropriate site-specific assumptions, then select compatible modules and inverters. Confirm permitting, utility interconnection requirements, equipment availability, and project costs before committing to a final design.

Question 2. A crew is installing a roof-mounted PV array on a composition-shingle roof. The approved plans specify a particular mounting system and roof attachment locations. During installation, a worker discovers that one specified attachment location would fall directly over a roof valley where water runoff is concentrated. What is the most appropriate response?

A. Relocate the attachment to a suitable structural location, verify that the revised arrangement meets engineering and manufacturer requirements, and obtain any required design approval before proceeding.

B. Install the attachment at the specified location and apply additional roofing sealant around the penetration.

C. Omit the attachment because the remaining mounts will probably support the array.

D. Install the attachment wherever the roof sheathing appears thickest, even if the location differs from the approved structural design.

Correct Answer: A. Relocate the attachment to a suitable structural location, verify that the revised arrangement meets engineering and manufacturer requirements, and obtain any required design approval before proceeding.

Answer Explanation:

Roof-mounted solar arrays transfer wind, gravity, and other applicable loads through the mounting system into the building structure. Attachment locations therefore cannot be changed casually or selected solely because a surface looks strong. A roof valley concentrates water runoff, increasing the importance of preserving the roof’s drainage and weatherproofing integrity. The contractor should stop work at the affected location, identify a suitable alternative attachment point, and verify structural capacity, mounting-system compatibility, and the required attachment spacing. The revised arrangement must satisfy the approved engineering design, applicable building requirements, and manufacturer instructions. Where the change affects approved plans, the appropriate design professional or authority must review it before installation continues.

Why the Other Options Are Incorrect:

B. Install the attachment and apply additional sealant — Incorrect.

Sealant cannot compensate for an unsuitable structural attachment location or guarantee long-term waterproofing. The attachment arrangement must be appropriate before the penetration is made.

C. Omit the attachment — Incorrect.

Removing a specified attachment can compromise the mounting system’s ability to resist design loads. The contractor must establish an acceptable alternative rather than simply reducing the number of mounts.

D. Choose a location based on apparent sheathing thickness — Incorrect.

Visual appearance alone does not establish structural adequacy. Attachment selection must account for framing, load transfer, fastener requirements, and the approved design.

Quick Study Guide:

Roof attachments must transfer array loads safely into suitable building structure. Follow engineered attachment spacing, approved mounting details, and manufacturer instructions. Before drilling, verify framing locations and identify drainage-sensitive areas. Seal roof penetrations using a compatible, approved weatherproofing method. When field conditions conflict with the plans, document the discrepancy and obtain the necessary design approval instead of improvising a structural change.

Question 3. A PV module has the following nameplate ratings:

• Maximum power: 400 W
• Voltage at maximum power: 40 V
• Current at maximum power: 10 A

A proposed string contains 10 identical modules connected in series. Assuming identical operating conditions and ignoring wiring losses, which result correctly describes the string at its maximum power point?

A. 400 V, 100 A, and 40 kW

B. 40 V, 100 A, and 4 kW

C. 4,000 V, 10 A, and 4 kW

D. 400 V, 10 A, and 4 kW

Correct Answer: D. 400 V, 10 A, and 4 kW

Answer Explanation:

In a series-connected string, the module voltages add while the string current remains approximately equal to the current of one module under the same operating conditions. Ten modules rated at 40 V each therefore produce a string voltage of 400 V at the maximum power point. The current remains 10 A, so power equals voltage multiplied by current: 400 V × 10 A = 4,000 W, or 4 kW. This also agrees with the combined module rating of 10 × 400 W = 4,000 W. Actual production varies with irradiance, cell temperature, shading, equipment behavior, and electrical losses. The calculated operating voltage must not be confused with the string’s higher potential open-circuit voltage.

Why the Other Options Are Incorrect:

A. 400 V, 100 A, and 40 kW — Incorrect.

The current does not multiply by ten when modules are connected in series. This option incorrectly treats a series string like ten parallel-connected modules.

B. 40 V, 100 A, and 4 kW — Incorrect.

This arrangement reverses the voltage and current behavior expected from a series connection. The voltages add, whereas the current remains approximately the same.

C. 4,000 V, 10 A, and 4 kW — Incorrect.

The calculated voltage is ten times too high. Ten modules at 40 V each produce 400 V, not 4,000 V, at the specified operating point.

Quick Study Guide:

For series-connected PV modules, add the individual voltages and retain approximately the same current. For parallel-connected strings, add the currents while maintaining approximately the same voltage. Calculate electrical power using P = V × I. Separately check maximum open-circuit voltage under the applicable cold-temperature conditions before determining whether modules, conductors, inverters, and disconnects have suitable voltage ratings.

Question 4. A contractor is designing a grid-connected PV system with battery storage. The homeowner expects the system to supply essential household loads during utility outages. Which design consideration is most important when selecting the backup arrangement?

A. Select a battery with the highest possible energy capacity and assume every existing household circuit can operate during an outage.

B. Identify the loads requiring backup, calculate their power and energy requirements, and select compatible storage, inverter, and transfer equipment capable of supplying them.

C. Use the PV array’s nameplate wattage as the sole basis for determining how long the battery can operate household loads.

D. Connect the battery directly to the utility service conductors so it can continue supplying the house whenever the grid fails.

Correct Answer: B. Identify the loads requiring backup, calculate their power and energy requirements, and select compatible storage, inverter, and transfer equipment capable of supplying them.

Answer Explanation:

Backup capability depends on more than battery capacity. The contractor must determine which circuits require power, their continuous demand, starting surges, and expected operating duration. Battery energy capacity, usable state-of-charge range, discharge limits, inverter continuous output, surge capability, and conversion losses all affect performance. The selected equipment must also support the intended operating mode, including safe isolation from the utility when required. Some systems support only designated backup loads, while others use equipment specifically designed for broader backup operation. The PV array’s nameplate rating alone cannot establish outage duration because sunlight, instantaneous demand, battery condition, and system losses change available energy. Equipment compatibility and approved installation requirements must also be verified.

Why the Other Options Are Incorrect:

A. Select the largest battery and assume all circuits can operate — Incorrect.

A large battery does not guarantee sufficient inverter power, compatible equipment, or support for every household circuit. Loads must be evaluated individually.

C. Use PV nameplate wattage alone to determine battery runtime — Incorrect.

Array wattage describes rated power under specified test conditions, not the amount of energy available throughout an outage. Battery capacity and actual load demand are also essential.

D. Connect the battery directly to utility conductors — Incorrect.

An improperly connected battery can energize circuits in an unsafe manner and create dangerous backfeed. Approved power-conversion and isolation equipment must be used.

Quick Study Guide:

Separate backup power calculations into power and energy. Power, measured in watts, determines whether the inverter can run a load; energy, measured in watt-hours or kilowatt-hours, determines how long it can operate. Account for startup surges, usable battery capacity, conversion losses, and expected demand. Verify approved transfer arrangements, equipment compatibility, and required utility isolation.

Question 5. A PV array is installed on a building subject to applicable rapid-shutdown requirements. During inspection, the electrical inspector discovers that the installation’s shutdown arrangement does not match the approved plans and the installed equipment’s listed configuration. The contractor argues that the inverter’s normal shutdown function is sufficient. What should the contractor do?

A. Explain that opening the utility main disconnect automatically satisfies every PV rapid-shutdown requirement.

B. Leave the installation unchanged because module-level shutdown equipment is unnecessary whenever an inverter has a shutdown button.

C. Verify the applicable rapid-shutdown requirements, the listed equipment configuration, and the approved design, then correct the installation and arrange the required inspection.

D. Add a warning label identifying the array as energized and treat the labeling as a substitute for the required shutdown arrangement.

Correct Answer: C. Verify the applicable rapid-shutdown requirements, the listed equipment configuration, and the approved design, then correct the installation and arrange the required inspection.

Answer Explanation:

PV rapid shutdown is intended to reduce electrical hazards for emergency responders and other personnel working around certain PV installations. Its requirements depend on the adopted electrical code, system configuration, equipment listing, and applicable exceptions. A normal inverter shutdown or opening the utility disconnect does not necessarily place every PV conductor in the required safe condition. The contractor must verify the approved design and the equipment manufacturer’s instructions, determine which shutdown functions are required, and correct any discrepancy before requesting acceptance. Labels communicate hazards and operating information, but they do not replace required electrical protection. The installation must satisfy the applicable code and approved system design rather than relying on an assumption that one shutdown control addresses every conductor.

Why the Other Options Are Incorrect:

A. Opening the utility main disconnect satisfies every requirement — Incorrect.

Disconnecting the utility supply does not necessarily eliminate hazardous DC voltage from the PV array or associated conductors.

B. An inverter shutdown button makes other shutdown provisions unnecessary — Incorrect.

The required shutdown performance depends on the applicable code and installed system configuration. A control button alone cannot establish compliance.

D. Add a warning label instead of correcting the installation — Incorrect.

Labels warn personnel about hazards but do not provide the electrical shutdown performance required by an applicable code.

Quick Study Guide:

Understand the difference between shutting down an inverter, disconnecting utility power, and satisfying PV rapid-shutdown requirements. Determine which rules apply to the specific installation and adopted code edition. Check equipment listings, conductor boundaries, shutdown controls, and manufacturer instructions. Labels supplement required protective measures; they do not replace them. Resolve discrepancies against the approved design before inspection.