Reviewed by WattCostLab Editorial Team
WattCostLab prioritizes primary public sources for energy prices, solar production methods and home-energy guidance.
EIA publishes U.S. retail electricity prices and state-level electricity price tables. WattCostLab calculator defaults are reference values only; users should enter their own utility rate.
EIA electricity prices →PVWatts estimates production from grid-connected photovoltaic systems using location and system inputs. It is a useful benchmark for validating location-specific PV production assumptions.
NREL PVWatts →DOE guidance covers home electrification and efficiency upgrades, including heat pumps, battery storage and electrical-panel considerations.
DOE Home Upgrades →The default $0.173/kWh used in several calculators corresponds to the EIA-reported 2025 U.S. annual average residential retail electricity price of 17.30 cents/kWh. It is not a recommended tariff and may differ substantially from a user's actual rate.
Electricity prices vary substantially by state and utility, while solar output varies by location, system orientation, losses and weather. Therefore WattCostLab keeps these assumptions editable rather than presenting one national value as universally applicable.
For quantitative defaults and methodological claims, preference is given to government agencies, national laboratories, standards bodies and original technical documentation. Commercial estimates may be discussed only when clearly labeled and should not replace local quotes.
The Electricity Cost by State tool uses final 2024 Electric Power Annual residential average revenue per kWh values. The U.S. average in that table is 16.48¢/kWh. EIA's separate 2025 national annual residential average is 17.30¢/kWh.
EIA notes that published average retail electricity prices are calculated from utility revenues divided by retail sales and are not the same as individual utility tariffs.
Brand-specific WattCostLab installation guides use current manufacturer support documentation for product and installation context. See Tesla Wall Connector Support and Powerwall Installation Documents. WattCostLab is not affiliated with Tesla.