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. New page

    State pages rewritten around what each state actually heats and drives with

    Pages: /heating/gas-vs-electric, /ev/ev-vs-gas

    • Each per-state page now shows what homes in that state heat with (natural gas, electricity, propane, fuel oil), what equipment they use (furnace, central heat pump, boiler) and what a household spends on heating, from the EIA Residential Energy Consumption Survey 2020 state tables; the EV pages show the state's registered EVs and plug-in hybrids (DOE AFDC, Dec 31, 2025) and its public charging locations and ports by level (DOE AFDC station counts, updated at each build).
    • Every page gets a written analysis for its own state and two state-specific questions in the FAQ. Every number in that text is a token filled from the data at build time, so a rate update changes the text; the build fails on any figure typed by hand, on a fact the survey does not report for that state, and on two states sharing wording.
    • All 50 states and DC are rewritten (the 25 states that had been bringing search traffic first, the rest the same day). A page is offered to search engines, and listed in the sitemap, only while its own written text is in place and passes those checks.
    • Breadcrumb data on the state pages pointed at the parent page with a doubled slash; fixed.

  2. New page

    Guides, named maintainer, state pages out of search

    Pages: /guides, /about

    • New /guides section: 13 guides, starting with a ranking of all 50 states and DC by residential electricity cost. Every price in a guide is computed from the same EIA data as the calculators at build time.
    • Home Kilowatt is now signed by its maintainer, Rodrigo Saran Gomes (About page and every calculator footer).
    • The per-state EV vs gas and gas vs electric heating pages are still available from the state picker, but are no longer offered to search engines: the main calculator for each already covers every state.

  3. Correction

    Space heater vs furnace: furnace size is the output rating

    Pages: /cost-to-run/space-heater-vs-central-heat

    • The furnace field said to enter the input rating from the data plate, while the formula divides by AFUE, which is only right for the output rating. Entering the input rating overstated the furnace cost by the AFUE factor (about 11% at 90%). The field now asks for the output (heating capacity) and explains how to convert an input rating. The formula and every result for the same output figure are unchanged.

  4. Policy

    Google AdSense connected

    Pages: all

    • Every page except the embedded calculators now loads Google's AdSense script, and /ads.txt names Google as the site's only authorized ad seller. This lets Google verify the site and review it for AdSense.
    • No ad units are shown yet. When they are, they stay outside and after the calculator, labelled "Advertisement", never beside the inputs or buttons. The Privacy Policy already describes AdSense and its cookies; it does not change.

  5. Policy

    Privacy: Cloudflare Web Analytics

    Pages: /privacy

    • The Privacy Policy now says the site uses Cloudflare Web Analytics: a script Cloudflare adds to each page that reports aggregate traffic (pages viewed, country, browser and device, referring site, page speed) with no cookies and no identifier for the visitor. Google Search Console and Google AdSense are described as before; there is no other analytics.

  6. Formula

    EV costs: no extra charging loss on EPA figures

    Pages: /ev/ev-vs-gas, /ev/charging-cost, /ev/phev-vs-ev-vs-gas, /ev

    • The EPA measures kWh per 100 miles at the wall, so charging losses are already in the rating. The EV vs gas, charging cost and 5-year cost calculators, and every state page, no longer add 12% (×1.12) on top: EV energy costs are about 11% lower than before. Example: a Tesla Model 3 RWD in Texas now costs an estimated $0.040 a mile to charge at home.
    • The charge-time calculator keeps its 0.9 factor: it converts the charger's power into energy stored in the battery, which is a different step.
    • The reference formulas, the test cases and the specification were corrected together; the site passes all 210 test cases.

  7. Constant

    Prices updated to EIA, August 2026

    Pages: all

    • Electricity: EIA residential prices for August 2026, all 50 states, DC and the US average (they replace the 2025–26 reference values). Natural gas: EIA 2025 annual average, residential, $/Mcf ÷ 10.37 therms; Connecticut, Maine, Maryland, North Carolina, Oklahoma, Rhode Island and South Carolina use 2024, their latest published year.
    • Every estimate, worked example, question and state page is computed from the new prices; the figures written in the page text come from the calculator at build time, so a monthly update never leaves an old number on a page. A sentence whose figure the calculator cannot reproduce, or whose meaning would change (a saving that became a cost), is left out until it is rewritten.
    • Propane, heating oil, gasoline and the average monthly bill are not in the EIA update and stay 2025–26 reference values; the pages label them that way.

  8. New page

    A page for every state: gas vs electric heat and EV vs gas

    Pages: /heating/gas-vs-electric, /ev/ev-vs-gas

    • 102 new pages: /heating/gas-vs-electric/ and /ev/ev-vs-gas/ for the 50 states and DC. Each shows the state's prices and climate data with their source and date, a worked example computed by the calculator, three questions answered with the state's own numbers, and nearby states. The calculator starts on that state; you can change it.
    • The text is chosen from the state's own data (price and climate bands, then a fixed variant), so no two pages read alike; the build fails if any two share more than 85% of their text beyond the common layout.
    • Nearby states are the states that share a boundary in the U.S. Census Bureau county adjacency file (2024); it counts boundaries through rivers and lakes and the Four Corners point. Alaska lists the other state in its climate zone; Hawaii lists the 4 states with the closest electricity rate.
    • Prices on these pages read "EIA reference 2025–26 (data as of 2026-09-26)", like the rest of the site, until the monthly EIA update is published. Gasoline is cited as "EIA weekly regional / AAA state averages, 2025–26 reference".
    • The by-state table on both calculators links each state to its page.

  9. Constant

    EV model details: only what the EPA publishes

    Pages: /ev/charging-cost

    • Each model has a short note with its EPA kWh per 100 miles and EPA range, for the exact model year and trim, with "Efficiency and range: U.S. EPA, fueleconomy.gov." The EPA data has no battery size, so no battery capacity is shown.

  10. Formula

    Monthly price update

    Pages: all

    • A monthly script reads residential electricity prices (the latest month with a price for every state) and residential natural gas prices (the latest annual average; a single month swings with the season) from the EIA API and updates the state data on the 25th of each month.

  11. Constant

    EV charging cost: 30 models with EPA figures

    Pages: /ev/charging-cost

    • The model picker lists 30 electric vehicles. Each one is a single EPA record from fueleconomy.gov (vehicle data file, data as of 2026-09-18): the EPA label kWh per 100 miles and the EPA combined range, with the model year.
    • The 8 models the site already used keep the same kWh per 100 miles; each now names the EPA record it comes from. The EPA data has no battery capacity, so the charge-time calculator keeps its 8 models.

  12. Formula

    Formula corrections in the topic calculators

    Pages: /heating/furnace-size, /solar/panels-needed, /solar/lease-vs-buy, /efficiency/attic-insulation, /efficiency/window-replacement

    • Furnace size: the result now rounds the furnace input up to the sizes sold (40,000, 60,000, 80,000, 100,000 or 120,000 BTU/h), as the method describes (R2-B8).
    • Solar panels needed: the roof area uses the whole number of panels, e.g. 20 panels × 18 sq ft = 360 sq ft (R2-D4).
    • Solar lease vs buy: yearly savings now apply the state's net metering factor, as the payback and output calculators do. In net-billing and utility-dependent states the 25-year figures are lower than before (R2-D10).
    • Attic insulation and window replacement: the cooling saving is kWh = BTU ÷ (SEER 14 × 1,000). The earlier figure also divided by 3,412 and was about 3.4 times too low (X14).
    • The reference formulas, the test cases and the specification were corrected together; the site passes all 210 test cases.

  13. Formula

    How the topic calculators present results

    Pages: /heating, /cooling, /solar, /generators, /ev, /efficiency

    • Sizing: the BTU, mini split and multi-zone calculators keep the nearest standard size and add the next size up; a load below the smallest unit reads "smaller than the smallest unit", never "0 BTU" (R2-C1, R2-C2, R2-C4).
    • Heat pump payback and heat pump water heater: a payback over 30 years reads "More than 30 years"; zero or less reads "Paid back at install" (R2-B5, R2-B13).
    • Heat pump and resistance options have no efficiency input, since the calculation uses the seasonal COP or 100% (R2-B1). The thermostat setback calculator has an AFUE input (default 0.90) and the full fuel list (R2-B11).
    • Heat pump vs propane or oil has a propane / oil toggle (R2-B2). Propane vs electric and gas vs electric show the heat pump as a third line (R2-B3). The wood stove comparison shows its fixed 0.90 gas furnace AFUE (R2-B9).
    • Tankless vs tank shows yearly costs only; there is no installation-cost input, so no payback (R2-B12). Net metering savings takes the export credit as your input, default 0.25 (R2-D3).
    • No state data, no table: state rebates link to DSIRE (R2-B7, R2-D2); outage hours (R2-D7) and peak sun hours (R2-D11, with the NREL map) are inputs; there is no per-state SEER2 minimum (R2-C7); charger rebates say "check your utility" (X9).
    • Values that follow the reference model are labelled "typical" or "our estimate": the peak pellet month (R2-B10), portable vs window gap (R2-C6), dehumidifier watts (R2-C10), duct table (R2-C11), panel direction factors (R2-D5), battery with no running cost (R2-D9), the 12-month curve (E3), and the ×1.08 preconditioning range (X11).
    • Generators: diesel is priced as heating oil + $0.30/gal and fuel prices read "EIA/AAA, 2025–26 reference (data as of 2026-09-26)" (X1, X2); standby exercise fuel is priced as propane (X5). The 3,500 W page keeps the default checklist (X19).
    • EV: the charger calculator shows 7.2 kW typed and 7.7 kW for 32 A Level 2 (X12); charging loss 1.12 and charge-time efficiency 0.9 are kept as specified (X13). The model list has the 8 vehicles with EPA figures; more are coming (X8).
    • Efficiency: LED and thermostat prices are inputs with the reference defaults, $3 and $200 (X18); smart thermostat COP and cooling hours by zone are cited as Home Kilowatt model values (X16).
    • The 30C notice ships on the charger installation page and the EV hub: the federal credit for home charger installation ended for property placed in service after June 30, 2026 (X10).
    • One page with a state or model picker for now: gas vs electric by state (R2-B4), solar payback and net metering by state, EV vs gas by state (X6) and charging cost by model.

  14. New page

    50 topic calculators

    Pages: /heating, /cooling, /solar, /generators, /ev, /efficiency

    • Heating (13), cooling and sizing (9), solar and batteries (9), generators (7, with four "what can it run" sizes), electric vehicles (6) and home efficiency (6), each with state prices and climate data, the formula and its sources.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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 2026-10-25: rates, gas prices and average bills for 50 states, DC and the US average are shown as "EIA, August 2026". Every calculator page carries "Last reviewed: 2026-09-26".

Spotted something that should be here? [email protected]