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Stuff Every Solar Owner Should Know

Home solar and batteries: how they work, sizing, safety, incentives and maintenance.

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  1. About how much power does a single solar PV cell typically produce?
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    About 1 or 2 watts. One cell is tiny. That is why cells are wired together into panels (modules), and panels into arrays, to power a home.

  2. What kind of electricity do solar PV cells generate?
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    Direct current (DC). Solar cells produce direct current, which flows in one direction. Homes and the grid run on AC, so an inverter converts it.

  3. What does a solar inverter do?
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    Converts DC panel power into AC household power. Panels produce DC electricity. Household appliances and the grid use AC, so the inverter does the conversion.

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  1. About how much power does a single solar PV cell typically produce?
  2. What kind of electricity do solar PV cells generate?
  3. What does a solar inverter do?
  4. Where is a microinverter installed in a rooftop solar system?
  5. With a string inverter, what happens if one panel on the string is shaded?
  6. How do solar cells become a home solar system?
  7. How many watts are in one kilowatt (kW)?
  8. What is a kilowatt-hour (kWh)?
  9. Which unit tells you how much energy a home battery can store?
  10. About how much electricity does the average US home buy per month, in kWh?
  11. In EIA's 2022 data, which state had the lowest yearly electricity purchases per residential customer?
  12. NREL's PVWatts manual uses what default value for total system losses when estimating solar output?
  13. NREL's PVWatts manual lists what default azimuth for a fixed array in the northern hemisphere?
  14. NREL's current PVWatts (Version 8) uses a default DC-to-AC ratio of 1.2. What does that mean?
  15. When a PV array briefly produces more power than the inverter's AC rating, what happens?
  16. Panel power ratings use a reference sunlight level. What irradiance is that reference in NREL's PVWatts?
  17. What default inverter efficiency does NREL's PVWatts use?
  18. Which kind of location generally receives the most sunlight (insolation)?
  19. Denver, near 40 degrees latitude, gets about how much more solar energy in June than in December?
  20. When does the greatest amount of solar energy reach the earth's surface?
  21. Solar radiation data for PV is often given in what units?
  22. Under net metering, what does your electric meter do when your solar sends extra power to the grid?
  23. Under a "net purchase and sale" setup, what does the utility usually pay for the solar power you export?
  24. Why does a basic grid-tied solar system shut off during a power outage?
  25. What do traditional 'grid-following' inverters need to operate?
  26. Will every solar-plus-battery system keep your home powered during a grid outage?
  27. As of October 2026, can you claim the federal residential solar credit (25D) for a system installed this year?
  28. Before it ended, what percent of qualified costs did the federal residential clean energy credit cover?
  29. For the federal credit through 2025, how large did a home battery have to be to qualify?
  30. If your tax liability was too low to use the whole 2025 solar credit, what could you do?
  31. What future shading risk does DOE tell homeowners to think about before installing solar?
  32. According to EIA, a PV system can make energy equal to what was used to build it within about how long?
  33. How long do most PV systems operate, according to EIA?
  34. According to EIA, state-of-the-art PV module efficiency is now approaching what level?
  35. EIA classifies a PV system as 'small-scale' if its capacity is under what size?
  36. What does it mean for a small solar inverter to 'ride through' a grid disturbance?
  37. How can solar charge a home battery, according to DOE?
  38. Which battery chemistry do most US utility-scale battery systems use, per EIA?
  39. On thick cloudy days, how much can the direct beam of sunlight be reduced?
  40. What should you confirm about a solar installer before signing a contract?
  41. DOE says to compare solar quotes by converting each one to what number?
  42. What does DOE suggest you ask an installer about who will actually do the work?
  43. DOE says to ask your installer to put what roof-related items in the proposal?
  44. DOE calls certification from which organization the solar industry standard for installers?
  45. What is DOE's rule of thumb for how long an installer should have been in business?
  46. Which of these should a solar installer you are considering be able to give you?
  47. Once permits are done, how long does DOE say the physical PV installation generally takes?
  48. Who usually obtains the local permits and arranges inspections for a home solar install?
  49. Under most solar lease agreements, who is generally responsible for system maintenance?
  50. In a solar power purchase agreement (PPA), what do you agree to buy?
  51. What is a solar co-op?
  52. How often should you expect an inverter to need replacing during a 25-year PV array's life?
  53. What feature do DOE's smart inverters add that helps utilities manage the grid?
  54. According to EIA, most PV systems in the United States are what type?
  55. By the late 1970s, where were PV panels providing electricity, according to EIA?
  56. When a generator runs for backup power, how far from windows, doors and vents should it be?
  57. When running a generator during an outage, what kind of CO detector does CDC recommend?
  58. At what height does OSHA require fall protection in the construction industry?
  59. What voltage does AFDC say Level 2 home EV charging equipment uses?
  60. Which home charging equipment comes with the vehicle, according to AFDC?
  61. If your home lacks capacity for Level 2 charging, who can add circuits, per AFDC?
  62. Which NABCEP credential focuses on energy storage (battery) systems?
  63. How many CEUs does NABCEP say PV Associates need to renew their Associate credential?
  64. Which national code is on NABCEP's PV Associate exam reference list?
  65. The NEC's rapid shutdown rule for rooftop solar mainly aims to protect whom?
  66. In which edition of the National Electrical Code did PV rapid shutdown rules first appear?
  67. When power optimizers shut down, about how much voltage does NREL say each one outputs?
  68. When a string inverter shuts down after losing grid power, what part stays energized in daylight?
  69. According to NREL, how does an arc fault in DC wiring compare with one in AC wiring?
  70. While installing or servicing solar panels, what does OSHA say employers should have workers do to the panels?
  71. Under the NFPA 1 Fire Code, how wide must roof access pathways be on homes with solar panels?
  72. NFPA 1 requires at least one roof access pathway on a solar home to be on which side?
  73. Why does NFPA 1 require solar panels on sloped home roofs to be set back from the ridge?
  74. OSHA treats solar panel maintenance as general industry work. At what fall height is protection required?
  75. What does OSHA say solar workers should never do while climbing a ladder?
  76. Near skylights on a solar job, OSHA says employers must guard them or have workers use what?
  77. How far does OSHA say solar workers must stay from overhead power lines?
  78. What does NREL's operations and maintenance guide recommend for cleaning PV modules?
  79. Besides cutting output, what problem can uneven dirt like bird droppings cause on solar panels?
  80. NREL says failure of which component is one of the most frequent causes of lost PV performance?
  81. If snow is never cleared from solar panels, about how much yearly production does NREL say is lost on average?
  82. NREL says snow tends to slide off solar arrays tilted more than about how many degrees?
  83. A salesperson says the federal government pays for your solar power. What does a federal consumer advisory call that?
  84. A federal solar advisory warns you to be careful about signing documents where?
  85. Treasury's solar consumer advisory says the right to cancel a solar transaction lasts at least how long?
  86. With PACE solar financing, how is the loan usually repaid?
  87. Once you have rooftop solar, what does the FTC say you will usually still pay your utility?
  88. Per the Department of Energy, how does recycling a solar panel usually cost compared with landfilling it?
  89. Why might some discarded solar panels count as hazardous waste under EPA rules?
  90. Across published field studies reviewed by NREL, about how much output do PV modules typically lose per year?
  91. A location has 3.5 peak sun hours. What does that mean?
  92. What does a solar panel's performance warranty guarantee?
  93. Why should you check a roof's shading at different times of year before going solar?
  94. California's net billing tariff applies to rooftop solar customers who apply to connect on or after what date?
  95. California's 2022 solar tariff aims to encourage solar exports during which hours?
  96. A home battery is rated 5 kW and 10 kWh. What does the kW rating describe?
  97. A battery is drained each day down to 65% of its capacity. What is its depth of discharge?
  98. A 10 kWh battery operating at a 90% depth of discharge has how much usable capacity?
  99. In NREL's guide, what typically counts as one battery cycle?
  100. In Florida, an HOA may choose where solar collectors go on the roof but must allow them to face which direction?
  101. In Texas, which is a reason a property owners' association may restrict a roof-mounted solar device?
  102. What does NREL say is making automated remote monitoring more feasible on small residential systems?