Home Kilowatt

Changelog

Changelog

Every change to a rate, constant or formula on Home Kilowatt, newest first. When a number on the site changes, it's recorded here with the date and the pages it affects.

  1. Formula

    Calculator inputs aligned with the reference formulas

    Pages: /cost-to-run/window-ac, /cost-to-run/central-ac, /cost-to-run/mini-split, /cost-to-run/hot-tub, /cost-to-run/dryer, /cost-to-run/dishwasher, /cost-to-run/refrigerator, /cost-to-run/well-pump

    • Each calculator shows only the inputs its formula uses; every result matches the three worked test cases for that page.
    • Window AC and Central air: watts come from BTU ÷ CEER and tons × 12,000 ÷ SEER2. A separate "enter watts directly" field is not offered.
    • Mini split: the average-watts line is labelled with the modulation factor you enter (for example 70%), not a fixed 60%.
    • Hot tub: the result covers the heater (watts × heater hours). Circulation-pump watts and a climate picker are not inputs; the climate appears as typical heater hours (warm 0.8, mild 1.2, cold 1.8). Add a pump as its own row with the Appliance calculator.
    • Clothes dryer: electric (3.0 kWh/load) and heat pump (1.2 kWh/load). A gas option is not offered until the gas-price formula is added.
    • Dishwasher: "Loads per month" sets the number of cycles; a separate loads-per-week field is not used.
    • Refrigerator & chest freezer: yearly kWh from the EnergyGuide label only.
    • Well pump: pump size (HP) and gallons per day only; the month is 30 days.

  2. Constant

    Appliance presets from energy.gov

    Pages: /cost-to-run/appliance

    • The Appliance calculator lists typical wattages from energy.gov, "Estimating Appliance and Home Electronic Energy Use". Where energy.gov gives a range, the preset is its midpoint rounded to 10 W: Clock radio 10 W (10 W); Coffee maker 1050 W (900–1,200 W); Clothes iron 1400 W (1,000–1,800 W); Hair dryer 1540 W (1,200–1,875 W); Microwave oven 930 W (750–1,100 W); Toaster 1100 W (800–1,400 W); Toaster oven 1225 W (1,225 W); Vacuum cleaner 1220 W (1,000–1,440 W); Laptop 50 W (50 W); Desktop computer (CPU, awake) 120 W (120 W); Computer monitor (awake) 150 W (150 W); Flat-screen TV 120 W (120 W); Stereo radio 240 W (70–400 W); DVD player 20 W (20–25 W); Window fan 150 W (55–250 W); Furnace fan 750 W (750 W); Whole-house fan 500 W (240–750 W); Water bed (heater, no cover) 250 W (120–380 W).
    • Appliances that have their own Home Kilowatt calculator link to it instead of presetting a wattage.

  3. Constant

    Electric bill estimator: example rows named

    Pages: /cost-to-run/electric-bill-estimator

    • The example list uses the reference defaults: space heater 1,500 W × 6 h, refrigerator 150 W × 8 h (the Refrigerator calculator default in the reference formulas), water heater element 4,500 W × 2.6 h.

  4. Formula

    Seasonal curves use a typical US pattern

    Pages: /cost-to-run/space-heater, /cost-to-run/electric-blanket, /cost-to-run/pool-pump, /cost-to-run/dehumidifier

    • The 12-month curve spreads the yearly cost with one typical monthly share of heating or cooling degree-days (NOAA 1991–2020 normals) for every state. Per-state monthly patterns are planned.

  5. New page

    Constants reviewed; first release

    Pages: all

    • Home Kilowatt launches with 20 cost-to-run calculators, the Electric Bill Estimator, and the Methodology and Data pages. Electricity and gas prices start from 2025–26 reference values and switch to the monthly EIA series with the first update. All incentive notes follow 2026 rules: the federal 25C and 25D tax credits ended for installations after Dec 31, 2025.
    • Reference data pack dated 2026-09-26: rates, gas prices and average bills for 50 states, DC and the US average are shown as "EIA reference 2025–26". Every calculator page carries "Last reviewed: 2026-09-26".

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