YepWatt

How YepWatt Calculates Your Bill

Each estimate comes from your utility’s published rate schedules and a typical hourly usage pattern for homes in its area. This page explains how the estimate is figured, where the rates and patterns come from, and what the estimates leave out.

What YepWatt calculates

YepWatt estimates monthly and annual electric bills for homes on selected residential rate plans of Georgia Power Company, Pacific Gas and Electric Company, and Sacramento Municipal Utility District (listed under Rate schedules and dates). It covers bundled service, where the utility supplies both the electricity and its delivery, and it uses the rate schedules each utility publishes.

The estimates handle the parts of a rate plan that set a home’s bill: tiered prices that depend on the month’s total use, time-of-use prices that depend on the hour, seasons, separate weekday and weekend schedules (holidays listed in a rate schedule are billed like weekends), fixed daily or monthly charges, per-kWh adjustments such as fuel charges, and charges figured as a percentage of other charges. Every charge in the rate schedule that sets the bill is included, except taxes, local charges, and the other items named under What’s not included.

How the estimate works

  1. For each month of the current year, your monthly kWh is spread over the days and hours with the typical hourly pattern for your type of home. Weekdays and weekends have different patterns, and holidays use the weekend pattern.
  2. If you shift evening use, that share of each day’s use from 5 p.m.–9 p.m. moves evenly to midnight–6 a.m., and your total use stays the same.
  3. Your EV’s monthly kWh at home is its efficiency (kWh per 100 miles) × miles a year ÷ 100 ÷ 12 × the share charged at home. It is added evenly to each charging hour, every day.
  4. Each hour is matched to the plan’s time period for that month and day, priced at the plan’s rate, and added up. The fixed charge (a monthly amount, or a daily amount times the days in the month), the per-kWh adjustment, and any credit you qualify for are separate lines. Each line is rounded to the cent, and the bill is the sum of the lines.
  5. On a tiered plan, the price depends on the month’s total kWh, not the hour. Use up to the tier limit is priced at the first tier’s rate, and use above it at the next tier’s rate. When the limit is a share of your baseline allowance, the allowance is the daily amount for your territory, heating type, and season times the days in the month.
  6. A baseline credit is figured on the month’s total kWh up to your baseline allowance (the daily amount times the days in the month) and shown as its own line, whatever the time of day.
  7. Some plans add charges that are a percentage of other charges: of the base bill (the fixed charge and electricity usage), or of all the charges before them, before taxes. These come after the other lines and are figured on the rounded amounts, then rounded to the cent. When a percentage depends on one of your answers in the calculator, the percentage for your answer is used.
  8. The annual estimate adds up 12 monthly bills at the rates in effect now. Every plan gets the same usage, so the differences come only from the rates.
  9. If a plan’s rates are being rechecked, for example after a scheduled rate change, the calculator shows its estimate at the last checked rates and stops ranking it until the check is done.

Usage patterns

The calculators spread your monthly kWh over the hours of the day with a typical hourly pattern for homes in your utility’s area, one for houses and one for apartments. The patterns come from building energy models calibrated to measured data, not from measurements of real homes, so your own pattern, and your bill, can differ.

An area is approximated by whole counties that the utility mostly serves. A pattern built from fewer building models is less certain.

How the patterns are made

  1. The source is the End-Use Load Profiles for the U.S. Building Stock, the ResStock results published as 2021/resstock_amy2018_release_1, which model homes with the actual weather of 2018. YepWatt uses the total electricity use of all modeled homes of each type in each county of the area.
  2. The published correction factors for heating and cooling use are applied. They scale the modeled heating and cooling use so it matches each state’s monthly electricity sales.
  3. The use is added up for each hour of local clock time, including daylight saving time, because rate periods follow the clock.
  4. Each hour of the day is averaged separately for each month, for weekdays and for weekends. Federal holidays are left out of both.
  5. Each day’s hourly averages are divided by their total, so each hour gets a share of the day’s use. For each month, the ratio of a weekend day’s use to a weekday’s is kept too.

The patterns don’t include EV charging, which the calculators add separately, and rooftop solar output isn’t subtracted from them.

Attribution and license

Data includes information from the ResStock™ dataset developed by the National Laboratory of the Rockies (NLR) with funding from the U.S. Department of Energy (DOE). The data is licensed under CC BY 4.0. YepWatt modified the data: the usage patterns on this site are derived from the End-Use Load Profiles for the U.S. Building Stock by the steps above and aren’t the published data.

Rate schedules and dates

Each plan’s rates are entered by hand from the utility’s official rate schedule and checked against it. For each plan, the lists give the date the rates in use took effect, the date they were last checked against the official schedule, and the documents they come from. When a rate schedule changes, the plan is marked under review until it’s checked again (see Plan status).

Georgia Power

PG&E

SMUD

What’s not included

Taxes and local charges aren’t included. For each utility, these are:

Also not included:

The calculators don’t cover selling power from rooftop solar and net metering, battery storage, separately metered EV charging, demand charges, retail plans from other suppliers in deregulated states, low-income discounts, the generation charges of community choice aggregators (CCAs) in California, event pricing such as critical peak pricing, flat-bill plans priced from past use, prepaid plans, plug-in hybrids, and EV incentives and tax credits. For the account conditions the calculator asks about, it says what it can’t estimate instead of showing a total that leaves the cost out.

Plan status

EV charging

EV efficiency is the EPA combined rating in kWh per 100 miles from FuelEconomy.gov web services (U.S. Department of Energy and U.S. EPA). The rating includes charging losses, so the calculators don’t add any. The vehicle presets were retrieved on October 5, 2026, and you can enter your own vehicle’s efficiency instead. How the EV’s kWh is added to your home’s use is under How the estimate works.

The comparison with gas uses the fuel economy and gas price you enter, and covers only the miles you charge at home.

State averages

The state pages and each utility page show the state’s average residential electricity price and monthly bill next to the estimates. These averages are background only: no estimate uses them.

They come from the U.S. Energy Information Administration (EIA) monthly retail sales data for the residential sector. EIA’s average price is the revenue that utilities in the state collected from homes, divided by the kWh they sold. The revenue includes customer charges and other fixed charges along with energy charges, and the average mixes every utility and rate plan in the state, so it doesn’t equal the price per kWh on any rate plan.

EIA’s data is in the public domain, and YepWatt credits EIA as its source: