Why the Questions Matter
The residential energy market of 2026 is full of hardware — solid-state batteries, bidirectional V2H chargers, hydrogen microgrids, smart panels — and full of installers who will happily sell you all of it. The difference between a system that works for 20 years and one that trips, degrades, or underperforms is decided in the first meeting: the questions you ask. This guide is the condensed version of our 50-question installer vetting playbook — the exact questions a consumer-advocate engineer asks, with what to look for in the answer.
The Five Phases of a Proper Interview
Phase 1 — Sizing & electrical engineering (Q1–10): continuous vs surge inverter ratings, Locked Rotor Amps on your AC compressor, split-phase 120/240V balancing, and DC PV oversizing ratios. Phase 2 — Battery chemistry & safety (Q11–20): LFP thermal stability, solid-state architectures, and recycling. Phase 3 — Hydrogen & fuel cells (Q21–30): natural-gas fuel cells, electrolyzer efficiency, metal-hydride storage safety. Phase 4 — Smart panels & VPPs (Q31–40): Span vs Leviton breakers, transfer switch types, grid-arbitrage logic. Phase 5 — Financials & warranties (Q41–50): the 30% ITC, Section 45V hydrogen credits, and 10-year vs lifetime battery warranties.
Q1. How will you size the continuous output of the inverter/battery system to handle my central air conditioner's starting surge (Locked Rotor Amps - LRA), and will I need a soft-starter? WHAT TO LOOK FOR: Look for an installer who calculates the actual starting current (LRA) of the compressor motor, ra
Look for an installer who calculates the actual starting current (LRA) of the compressor motor, rather than just matching average running kilowatts. They must e…
Q2. How will the system handle split-phase 120/240V load balancing, and what is the maximum permissible neutral imbalance before the inverter faults? WHAT TO LOOK FOR: Look for installers who understand split-phase winding balancing. They should verify that the loads are balanced across Phase A and Phas
Look for installers who understand split-phase winding balancing. They should verify that the loads are balanced across Phase A and Phase B to prevent neutral l…
Q3. What is the maximum DC photovoltaic (PV) array oversizing ratio supported by the inverter, and how does this affect low-irradiance winter performance? WHAT TO LOOK FOR: A highly competent installer will explain the benefits of DC array oversizing on cloudy or low-sun winter days, detailing MPPT limi
A highly competent installer will explain the benefits of DC array oversizing on cloudy or low-sun winter days, detailing MPPT limits, voltage acceptance window…
Q4. In an extended grid outage where the battery drains to 0%, does your system have an autonomous black-start capability to reboot itself and the solar arrays when the sun comes up? WHAT TO LOOK FOR: Look for confirmation of independent black-start capability. Without it, if a battery drains completely
Look for confirmation of independent black-start capability. Without it, if a battery drains completely, the system cannot reboot itself from solar arrays and r…
Q5. What math and parameters do you use to calculate my battery capacity (kWh) for multi-day autonomy, and what depth of discharge is assumed? WHAT TO LOOK FOR: Verify that the installer does not use a simplistic calculation. Sizing must account for daily consumption, desired autonomy (days of backup),
Verify that the installer does not use a simplistic calculation. Sizing must account for daily consumption, desired autonomy (days of backup), allowable depth o…
Q6. How does winter sub-zero temperature affect my home's heating loads and battery charging limits, and how is this factored into sizing? WHAT TO LOOK FOR: Look for installers who conduct rigorous seasonal load profiling and understand temperature derating. Low temperatures increase space heating loads
Look for installers who conduct rigorous seasonal load profiling and understand temperature derating. Low temperatures increase space heating loads while restri…
Q7. If integrating bidirectional Vehicle-to-Home (V2H) charging, what rate of power transfer is supported, and how does cold weather impact V2H battery health? WHAT TO LOOK FOR: Confirm the installer has experience with bidirectional EV charger wiring and knows how cold ambient temperatures degrade EV b
Confirm the installer has experience with bidirectional EV charger wiring and knows how cold ambient temperatures degrade EV battery charge/discharge efficiency…
Q8. What are the specific conductor sizing, crimping, and torque requirements for the high-current battery connections to prevent thermal hotspots? WHAT TO LOOK FOR: Look for strict adherence to National Electrical Code (NEC) standards, including the use of calibrated torque wrenches and specified compr
Look for strict adherence to National Electrical Code (NEC) standards, including the use of calibrated torque wrenches and specified compression lugs.…
Q9. What is the economic and operational benefit of a single point of connection grid meter configuration for multi-family apartment Virtual Power Plants? WHAT TO LOOK FOR: In shared microgrids, the installer must explain how a single shared utility connection point bypasses regulatory and physical hard
In shared microgrids, the installer must explain how a single shared utility connection point bypasses regulatory and physical hardware bottlenecks of individua…
Q10. What safety and power quality compliance standards will be integrated into the combiner box and inverter inputs? WHAT TO LOOK FOR: Verify that the installer includes comprehensive surge, ground-fault, and arc-fault protection in their single-line diagram. DETAILED TECHNICAL ANSWER: The system must u
Verify that the installer includes comprehensive surge, ground-fault, and arc-fault protection in their single-line diagram.…
Q11. Why are Lithium Iron Phosphate (LFP) battery chemistries preferred over traditional Nickel Manganese Cobalt (NMC) for residential storage? WHAT TO LOOK FOR: The installer should cite structural safety, longevity, and thermal stability differences between LFP and NMC chemistries. DETAILED TECHNICAL A
The installer should cite structural safety, longevity, and thermal stability differences between LFP and NMC chemistries.…
Q12. How does an All-Solid-State Battery (ASSB) eliminate the primary failure point and thermal runaway risks of conventional lithium-ion batteries? WHAT TO LOOK FOR: Look for an understanding of solid state technology, specifically the complete elimination of highly flammable liquid organic electrolytes
Look for an understanding of solid state technology, specifically the complete elimination of highly flammable liquid organic electrolytes.…
Q13. What is the technical benefit of a bipolar stacked battery cell architecture, and how does it affect module-level voltage and interconnections? WHAT TO LOOK FOR: The installer should explain how bipolar stacking connects cells in series internally within a single pouch, eliminating external wiring.
The installer should explain how bipolar stacking connects cells in series internally within a single pouch, eliminating external wiring.…
Q14. What is the material composition and function of the separator membrane in a true solid-state battery cell? WHAT TO LOOK FOR: Look for technical familiarity with solid-state separators. The separator must prevent dendrite growth and maintain high ionic conductivity. DETAILED TECHNICAL ANSWER: In tru
Look for technical familiarity with solid-state separators. The separator must prevent dendrite growth and maintain high ionic conductivity.…
Q15. How does the simultaneous charge and discharge capability of an ASSB work, and how does it benefit my residential microgrid? WHAT TO LOOK FOR: Verify that the installer understands bidirectional, simultaneous power flow within solid-state converters, which is impossible in conventional batteries. DE
Verify that the installer understands bidirectional, simultaneous power flow within solid-state converters, which is impossible in conventional batteries.…
Q16. What is the expected cycle life, annual energy retention, and lifespan of an advanced solid-state energy storage system? WHAT TO LOOK FOR: The installer should provide concrete warranty and cycle life metrics for solid-state battery cores, which significantly exceed LFP. DETAILED TECHNICAL ANSWER: W
The installer should provide concrete warranty and cycle life metrics for solid-state battery cores, which significantly exceed LFP.…
Q17. What is the minimum operating temperature threshold of my battery bank, and how much usable capacity is retained in extreme winter cold? WHAT TO LOOK FOR: Verify the battery's operating temperature range and ask for concrete retention figures at sub-zero temperatures (e.g. -40°C). DETAILED TECHNICAL
Verify the battery's operating temperature range and ask for concrete retention figures at sub-zero temperatures (e.g. -40°C).…
Q18. What are Gotion's new Gnascent sodium-ion battery specialized versions, and how do their energy densities and cold-weather discharge rates compare? WHAT TO LOOK FOR: The installer should explain sodium-ion battery technology, citing VW-backed Gotion's dedicated Gnascent brand and its three specializ
The installer should explain sodium-ion battery technology, citing VW-backed Gotion's dedicated Gnascent brand and its three specialized versions.…
Q19. What BESS site design safety best practices and permitting standards are recommended for residential and community storage projects? WHAT TO LOOK FOR: Look for installers who follow strict regional safety recommendations, such as the San Diego County BESS Best Practices guidelines. DETAILED TECHNICA
Look for installers who follow strict regional safety recommendations, such as the San Diego County BESS Best Practices guidelines.…
Q20. How does the heat dissipation and noise level of a solid-state battery system compare to conventional actively-cooled batteries? WHAT TO LOOK FOR: Confirm that the battery utilizes passive cooling rather than noisy active cooling fans, which create parasitic load and mechanical wear points. DETAILED
Confirm that the battery utilizes passive cooling rather than noisy active cooling fans, which create parasitic load and mechanical wear points.…
