Glossary
Plain-English definitions for the solar and pool terms behind every estimate. Each entry links straight to the calculator or guide where the number actually gets used — no jargon, no sales pitch.
Solar terms
21 TERMSDC-to-AC derate factor
The combined system losses that shrink a panel's DC nameplate rating down to usable AC power — a standard default is about 0.86 (a 14% loss).
Energy offset
The percentage of your yearly electricity use that your solar panels produce — a 100% offset means generation equals consumption over a year.
Inverter
The device that converts a solar array's DC electricity into the AC power your home and the grid use — the system's most failure-prone component.
Investment Tax Credit (ITC)
The federal Investment Tax Credit for solar — now available only through the commercial Section 48E pathway after the residential 25D credit expired in 2025.
Kilowatt (kW)
A unit of power equal to 1,000 watts — used to size a solar system (e.g. an 8 kW array).
Kilowatt-hour (kWh)
The unit of energy your utility bills you for — one kilowatt of power used for one hour.
Microinverter
A small inverter mounted under each individual panel that converts its DC output to AC on the spot, improving shade tolerance and per-panel monitoring.
Monocrystalline panel
The dominant residential solar cell type, cut from a single silicon crystal for the highest efficiency — roughly 19–22% — and a uniform black look.
NEM 3.0
California's net-billing tariff that credits exported solar at roughly a quarter of the retail rate, making batteries far more valuable.
Net metering
A utility billing arrangement that credits you for the solar electricity you export to the grid, offsetting the power you draw later.
Panel degradation
The gradual yearly loss of a solar panel's output — typically about 0.4–0.5% per year, so panels still make ~85–90% of original power at 25 years.
Payback period
The number of years it takes for a solar system's electricity savings to equal its net cost.
Peak sun hours
The number of hours per day that sunlight averages 1,000 W/m² of intensity — the key local input for estimating how much energy a solar array will make.
Performance ratio (PR)
How much of a solar system's theoretical output it actually delivers after real-world losses — usually expressed as a percentage around 75–85%.
Power purchase agreement (PPA)
A power purchase agreement where a company owns the panels on your roof and you pay only for the electricity they produce, at a set per-kWh rate.
Section 25D (residential solar tax credit)
The 30% federal residential clean-energy tax credit for homeowners who buy solar — expired December 31, 2025.
Section 48E (commercial clean electricity credit)
The commercial federal investment credit that a leasing or PPA company can claim on solar it owns — and pass through as a lower rate.
Solar battery (home storage)
A home storage battery that banks daytime solar for use at night or during outages — essential under net-billing tariffs like NEM 3.0.
Solar lease
A fixed monthly payment to rent a solar system a company owns and maintains — no upfront cost, but you don't own the panels or claim the tax credit.
SREC (Solar Renewable Energy Certificate)
A Solar Renewable Energy Certificate earned for each megawatt-hour your system produces, which you can sell for income in certain state markets.
String inverter
A single central inverter that converts the combined DC output of a series-wired panel string to AC — the lowest-cost inverter option for unshaded roofs.
Pool terms
16 TERMSCoping
The capped edging around a pool's rim that joins the shell to the deck — both a finished trim and a barrier that keeps deck water out of the pool.
Excavation
Digging and shaping the hole for an inground pool — an early build step whose cost swings widely with soil, access, and rock or high water tables.
Fiberglass pool
A pre-molded one-piece pool shell dropped into the excavation — faster and lower-maintenance, but size-limited.
Gunite (shotcrete)
A sprayed concrete shell that forms the most durable and fully customizable type of inground pool — and the most expensive.
Pebble finish
A premium gunite interior finish of small pebbles in cement that lasts about 15–25 years — more durable and textured than plain plaster.
Plaster finish (marcite)
The traditional cement-based interior finish troweled onto gunite pools — the cheapest finish, but the shortest-lived at about 7–15 years.
Pool decking
The paved surface surrounding a pool — a major budget line that's priced separately from the pool itself, by the square foot.
Resurfacing
Renewing a pool's worn interior finish — replastering, a new pebble surface, or a vinyl-liner swap — typically needed every 10–20 years.
Saltwater system (salt chlorine generator)
A system that makes chlorine from dissolved salt instead of you adding it — gentler water, lower chemical spend, higher upfront cost.
Skimmer
The intake opening at the waterline that pulls in floating debris before it sinks, feeding surface water to the pump and filter.
Spa combo (pool-spa combination)
An attached spa or hot tub built into the pool, sharing its structure and equipment and usually spilling over into the main pool — priced as an add-on.
Tile finish
A fully tiled pool interior — the most durable and expensive finish, prized for its appearance and decades-long lifespan.
Turnover rate
The time it takes a pool's pump and filter to circulate the entire water volume once — most pools aim to turn over fully every 8–12 hours.
Variable-speed pump (VSP)
A pool pump that adjusts its motor speed to run slow and efficient for most of the day — the single biggest electricity saver in pool operation.
VGB Act (Virginia Graeme Baker Pool & Spa Safety Act)
The federal Virginia Graeme Baker Pool & Spa Safety Act, which mandates anti-entrapment drain covers and related safeguards to prevent suction injuries.
Vinyl-liner pool
The lowest-cost inground pool type: a custom vinyl sheet draped over a steel or polymer frame, cheap upfront but the liner needs periodic replacement.