Understanding Denkiya's Cost and Savings Estimates

Denkiya helps you understand the true cost of running your home and vehicles on electricity versus fossil fuels. This page explains how we calculate the energy costs, vehicle and appliance running costs, and savings estimates you see in the app.

We want you to feel confident knowing exactly how the numbers are derived, using real-world energy prices and industry-standard efficiency data.

How We Calculate Energy Costs

Denkiya uses publicly available energy price data, primarily from the U.S. Energy Information Administration (EIA), to estimate what you pay for different fuels. We use the most recent full year of data for stability and consistency to provide you regionally accurate, data-driven comparisons across fuel types. Rates can vary seasonally; our displayed numbers typically reflect average, minimum, and/or maximum values for your state and calculated costs are rounded to the nearest cent for clarity and consistency.

Electricity

• We use average residential electricity rates for your State.
• Prices are reported in cents per kWh and converted to dollars per kWh.

Example:
If your state's average rate is 10.4¢/kWh → $0.10/kWh.

Natural Gas

• We use average residential Natural Gas rates for your State.
• Prices are reported in dollars per thousand cubic feet (MCF).
• We convert this to cost per therm (1 MCF ≈ 10.37 therms).

Example:
$3.00/MCF → $0.29 per therm.

Gasoline & Diesel

• We use your regional price for regular gasoline or no 2 diesel by PADD region, state or metro area when available. In the rare event that none of the above is available we fall back to the national average for that fuel type.
• Prices are reported in dollars per gallon.

Example:
National average = $3.07/gallon.

Propane

• We use the residential pricing for your PADD region price for propane, falling back to the national average when a PADD price is unavailable.
• Due to the warmer climate and a resulting lack of consistent, statistically significant pricing data, PADD 5 (West Coast) is excluded from the reported EIA dataset for this fuel type.
• Prices are reported in dollars per gallon, which is how propane is typically sold and delivered to homes.
• However, to allow for apples-to-apples usage comparisons with natural gas and electricity, propane is also converted to dollars per therm – a common energy unit.
• Propane contains approximately 91,500 BTUs per gallon, or about 0.915 therms per gallon.

Example:
National average = $2.50/gallon.
Converted to therms: $2.50 ÷ 0.915 = $2.73/therm.

Heating Oil

• We use the residential pricing for your PADD region price for heating oil, falling back to the national average when a PADD price is unavailable.
• Due to the warmer climate and a resulting lack of consistent, statistically significant pricing data, PADD 5 (West Coast) is excluded from the reported EIA dataset for this fuel type.
• Prices are reported in dollars per gallon, which is how heating oil is typically sold and delivered to homes.
• However, to allow for apples-to-apples usage comparisons with natural gas and electricity, heating oil is also converted to dollars per therm – a common energy unit.
• Heating oil contains approximately 138,500 BTUs per gallon, or about 1.385 therms per gallon.

Example:
National average = $3.48/gallon.
Converted to therms: $3.48 ÷ 1.385 = $2.51/therm.

Adding Your Own Energy Data

While Denkiya provides regionally accurate energy cost estimates using publicly available data, you can also add your own energy data for even more personalized calculations. This feature allows you to input your actual monthly electricity, natural gas, gasoline, diesel, propane, or heating oil costs to get more accurate estimates for your specific situation.

How to Add Custom Data

Click the “Add My Energy Data” button in the “My Energy Costs” section to enter your monthly energy consumption and costs. You can input up to 12 months of data for any energy source. The system will automatically calculate your annual average, high, and low costs based on your actual usage patterns.

Two Ways to Add Your Data

Manual Entry

Enter your most recent full year's worth of utility data manually by filling in the monthly consumption (kWh, therms, gallons, etc.) and cost fields. This method works for all energy sources and all utility companies and vendors. Simply gather your monthly utility bills or reciepts and enter the usage and cost data for each month.

Green Button Upload

For supported utilities, you can download your energy data directly from your utility's website using the Green Button standard and upload the ZIP file to automatically populate your data. This saves time and reduces manual data entry errors.

How to download your Green Button data:

1. Sign in to your utility's online account
2. Look for “Usage Details” or “Green Button: Download my data”
3. Select a date range (we recommend at least 12-24 months for accurate calculations)
4. Choose CSV format and download the ZIP file
5. Upload the ZIP file in Denkiya's “Add My Energy Data” modal

Solar Energy Considerations

If you have solar panels, your electricity costs may include net metering credits or negative values during months when you generate more electricity than you consume. When you add custom electricity data and have solar panels installed, Denkiya will display a single annual average cost instead of a range. This is because the high and low monthly values for solar users often include extreme variations (including negative costs during sunny months) that don't represent your true annual electricity cost.

Example: A solar user might see monthly costs ranging from -$50 (credit) to $200 (winter months), but their true annual average might be $75. In this case, we show $75 as the single cost rather than a misleading range.

True-up Billing: Many solar customers are on net metering plans with annual “true-up” billing cycles. Throughout the year, you may pay only minimum charges (often $10-20/month), but then receive a large bill at the end of the billing cycle to settle the difference between your consumption and generation. Simply enter your actual monthly bills as they appear, including any true-up charges in the month they occur. Denkiya will automatically calculate the correct annual average cost based on your total annual consumption and costs.

Important: If you're on net metering, make sure to include your true-up bill when entering your custom data. If you only enter the minimum monthly charges and omit the true-up amount, your per-kilowatt-hour cost will be artificially low and won't reflect your actual electricity costs.

Example: If you have 11 months of $15 minimum charges and one month with a $600 true-up bill, enter these amounts exactly as they appear on your bills. The system will calculate your true annual average cost from the total annual amount.

Outlier Detection & Data Filtering

When you upload your energy data, Denkiya automatically applies robust statistical filtering to identify and exclude extreme outliers that could skew your cost estimates. This ensures that one-off billing errors, credits, or unusual circumstances don't distort your representative high and low cost ranges.

How it works: We calculate monthly rates (cost ÷ usage) and use an asymmetric Interquartile Range (IQR) method to identify outliers. The system is more lenient with low rates (allowing legitimate seasonal lows) but stricter with high rates (catching billing errors or extreme spikes). This means a $0.30/kWh rate during a low-usage month will be included, while a $0.95/kWh billing error will be excluded.

What gets filtered: Extreme outliers like billing errors, one-time credits, or unusual circumstances that don't represent your typical energy costs. Normal seasonal variations and legitimate low/high rates are preserved.

Result: You get realistic high and low cost ranges that reflect your actual energy usage patterns, not distorted by billing anomalies or data entry errors.

Data Accuracy Disclaimer

Important: The accuracy of your cost estimates and savings calculations depends entirely on the quality and completeness of the data you provide. Please ensure that:

• Your monthly consumption and cost data is accurate and complete
• You include all relevant energy sources you use
• Your data represents a typical year of usage (accounting for seasonal variations)
• You update your data if your energy usage patterns change significantly

Denkiya will always prioritize your custom data over regional averages when available, but remember that “garbage in, garbage out” applies - the more accurate your input data, the more reliable your cost estimates and savings projections will be.

What is a PADD Region?

A Petroleum Administration for Defense District (PADD) is a geographic region defined by the U.S. government to help track and analyze petroleum distribution and pricing. Originally established during World War II, PADDs are still used today to organize and report fuel price data regionally, making comparisons more meaningful than national averages alone.

PADD Regions

How We Calculate Vehicle Running Costs

We help you compare the cost of driving an electric vehicle (EV), a gasoline vehicle, or a plug-in hybrid by first calculating cost per mile for each vehicle type.

Electric Vehicles

Watt hours per mile tells you how many watt-hours you use to travel 1 mile and is a common metric used to measure EV efficiency. For our purposes however Miles per Kilowatt Hour (mi/kWh) tells you how many miles you can travel per 1 kilowatt-hour of stored electricity and is a cleaner analogue to Miles Per Gallon.
Since 1 kWh = 1000 Wh, you divide 1000 by Wh/mile.

Examples:
250 Wh/mile → 1000 ÷ 250 = 4.0 mi/kWh
300 Wh/mile → 1000 ÷ 300 ≈ 3.33 mi/kWh

Formula:
Cost per mile = Electricity cost per kWh ÷ Vehicle efficiency (miles per kWh)

Example:
$0.12/kWh ÷ 3.5 mi/kWh = $0.03 per mile

Gasoline and Hybrid Vehicles

For gasoline and hybrid vehicles we use the same basic formula, but with the cost of gasoline or diesel per gallon instead.

Formula:
Cost per mile = Gasoline cost per gallon ÷ Vehicle efficiency (miles per gallon)

Example:
$4.00/gallon ÷ 25 mpg = $0.16 per mile

Plug-in Hybrid Vehicles

For plug-in hybrid vehicles we use a blended cost per mile formula that combines the cost of electricity and gasoline. You adjust the slider to indicate what % of the time you drive on gasoline vs. electric only miles.

Formula:
Blended cost per mile = (Electric cost per mile × Electric fraction) + (Gas cost per mile × Gas fraction)

Example:
($0.03 × 0.6) + ($0.16 × 0.4) = $0.08 per mile

Public Charging Adjustment

We apply a 2.5x max multiplier for public charging: 1 + (Public charging % ÷ 100) × 1.5 to account for the higher cost of charging at public stations. Becuase public charging costs may vary greatly depending on location and station host, etc. this multiplier is a rough approximation and may not reflect your actual local public charging costs.

Example:
20% public charging: $0.034 × 1.3 = $0.044 per mile

How We Calculate Vehicle Savings

Savings are calculated by comparing the average annual cost of driving an electric vehicle (EV) to the average annual cost of driving a comparable gasoline vehicle. Average annual cost is calculated by multiplying the cost per mile by your annual mileage in each case.

Formula:
Annual cost = Cost per mile × Annual mileage

Example:
$0.03 per mile × 15,000 miles/year = $450/year

Estimated savings: Gas equivalent vehicle annual cost – Electric vehicle annual cost

Example:
$1,920 (gas) – $528 (electric) = $1,392 saved per year

How We Calculate Dryer Savings

Dryer savings are calculated by comparing the annual cost of running your electric dryer to the annual cost of running a comparable gas dryer with the same usage patterns. This comparison helps you understand the cost difference between electric and gas drying methods.

Electric Dryer Costs

For electric dryers, we calculate the cost per load using your dryer's efficiency rating (Combined Energy Factor or CEF) and electricity rates. Energy Star uses Combined Energy Factor (CEF) to directly compare the energy efficiency of gas and electric clothes dryers in pounds per kWh. The higher the value, the more efficient the dryer is. To determine a dryer's CEF, you can visit Energy Star's website.

Formula:
Cost per load = kWh per load × Electricity rate per kWh

Example:
2.5 kWh per load × $0.12/kWh = $0.30 per load

Gas Dryer Costs

For gas dryers, we calculate the cost per load using both gas and electricity consumption (gas dryers still use electricity for the motor and controls). The CEF rating combines both electricity and gas usage, but since electricity and gas have different rates, we need to split these out for an accurate cost calculation.

We start with the CEF rating, then subtract the electricity usage (motors, controls) at your local electricity rate. The remaining energy represents gas usage, which we convert from kilowatt-hours to therms using your local gas rate. This ensures we don't double-count electricity usage and accurately calculate the cost of both fuel types:

Formula:
Cost per load = (kWh per load × Electricity rate) + (Therms per load × Gas rate per therm)

Example:
(0.25 kWh × $0.12/kWh) + (0.11 therms × $1.81/therm) = $0.03 + $0.20 = $0.23 per load

Annual Cost Calculation

We then calculate annual costs based on your usage patterns:

Formula:
Annual cost = Cost per load × Loads per day × 365 days

Example:
$0.30 per load × 3 loads/day × 365 days = $328.50 per year

Savings Calculation

Savings are calculated by comparing your electric dryer's annual cost to a gas dryer's annual cost:

Formula:
Annual savings = Gas dryer annual cost – Electric dryer annual cost

Example:
$251.85 (gas) – $328.50 (electric) = -$76.65 (you pay more with electric)

When the result is negative, it means your electric dryer costs more to run than a comparable gas dryer. When positive, it means you're saving money with your electric dryer.

Key Factors

• Dryer Efficiency: More efficient dryers (like heat pump dryers) use less energy per load
• Local Energy Rates: Electricity and gas prices vary significantly by region
• Usage Patterns: Number of loads per day and load size affect total annual costs
• Dryer Type: Heat pump dryers are typically more efficient than resistance electric dryers

Data Accuracy, Assumptions & Limitations

All calculations are based on the latest available data from the U.S. Energy Information Administration and the best available industry-standard efficiency factors. Actual costs and savings will vary based on your driving habits, usage, and local market conditions. Energy rates can vary as much as ±10–20% throughout the year. We use the most granular average data available for your area, then national averages as fallback.

Appliance usage, vehicle efficiency, annual mileage, charging habits, etc. are based on manufacturer specs, EPA estimates, representative usage patterns, or direct user input.

These estimates are intended to provide a realistic ballpark for electrification planning purposes – they are not exact predictions. Actual costs and savings will vary based on individual circumstances, and no guarantee of accuracy is implied or guaranteed.

Definitions

Miles Per Gallon (MPG) is a measure of how far a vehicle can travel on one gallon of fuel. It indicates the fuel efficiency of gasoline and diesel vehicles.

MCF stands for thousand cubic feet, a unit of measurement for natural gas volume. One MCF equals 1,000 cubic feet of natural gas.

Therm is a unit of heat energy equal to 100,000 British thermal units (BTUs). One MCF of natural gas contains approximately 10.37 therms of energy.

British thermal unit (Btu) is a commonly used measure of the heat content of fuel and other energy sources. It is the amount of heat needed to raise the temperature of one pound of water by 1 degree Fahrenheit.
1 kilowatt-hour = approximately 3,400 Btu
1 cubic foot of natural gas = 1,000 Btu
1 therm of natural gas = 100,000 Btu
One gallon of gasoline = about 120,000 Btu.

kW (Kilowatt) is a unit of power equal to 1,000 watts. It measures the rate at which energy is generated or consumed at a given moment. For example, a 5 kW solar array can generate up to 5 kilowatts of power in perfect conditions and when operating at full capacity.

kWh (Kilowatt-hour) is a unit of energy equal to the amount of energy used by a 1-kilowatt device running for one hour. It is the standard unit for measuring electricity consumption and storage capacity. For example, a 10 kWh battery can store 10 kilowatt-hours of energy, and an electric vehicle with a 75 kWh battery can store 75 kilowatt-hours of energy. It is calculated as: kWh = kW × hours of use.

Watt Hours Per Mile (Wh/mile) measures how much electrical energy an electric vehicle uses to travel one mile. It indicates the energy efficiency of electric vehicles.

Miles per Kilowatt Hour (mi/kWh) measures how many miles an electric vehicle can travel on one kilowatt-hour of electricity. It is calculated as: mi/kWh = 1,000 ÷ Wh/mile. This metric is the electric vehicle equivalent of miles per gallon for gasoline vehicles.

Atmospheric lifetime describes how long it takes to restore the system to equilibrium after an increase in the concentration of a GHG in the atmosphere. Atmospheric lifetimes of GHGs range from tens to thousands of years.

Carbon dioxide equivalent is a metric measure used to compare the emissions from various GHGs based upon their global warming potential (GWP). Carbon dioxide equivalents are commonly expressed as “million metric tons of carbon dioxide equivalents (MMTCO2e).” The carbon dioxide equivalent for a gas is derived by multiplying the tons of the gas by the associated GWP, as follows:

• MTCO2e = (metric tons of a gas) × (GWP of the gas)
• MMTCO2e = (million metric tons of a gas) × (GWP of the gas)

Carbon footprint refers to the total amount of GHG that is emitted into the atmosphere each year by a person, family, building, organization, or company. A person's carbon footprint includes GHG emissions from fuel that an individual burns directly, such as by heating a home or riding in a car. It also includes GHGs that come from producing the goods or services that the individual uses, including emissions from power plants that make electricity, factories that make products, and landfills where trash is sent.

Carbon neutral means having or resulting in no net addition of carbon dioxide to the atmosphere.

Carbon sequestration is the process by which trees and plants absorb carbon dioxide, release the oxygen, and store the carbon.

Emissions inventory is an estimate of the amount of pollutants emitted into the atmosphere from major mobile, stationary, area-wide, and natural source categories over a specific period of time, such as a day or a year.

Global climate change is the observed increase in the average temperature of the Earth's atmosphere and oceans, along with other significant changes in climate (such as precipitation or wind) that last for an extended period of time. The term global climate change is often used interchangeably with the term global warming, but global climate change is preferred over global warming because it helps convey that GHG emissions may result in other changes in addition to rising temperatures.

Global warming potential (GWP) is a measure of how much heat a greenhouse gas traps in the atmosphere relative to the effects of carbon dioxide (CO2) over a specific time period, allowing for comparisons of the warming potential of different gases. GWP allows for the conversion of different GHG emissions into the same emissions unit, carbon dioxide equivalence (CO2e).

Greenhouse gas (GHG) refers to gases that absorb and emit radiation within the thermal infrared range, which is the fundamental cause of human contribution to the greenhouse effect. Although there are many GHGs, the following six are explicitly identified as being of primary concern:

• Carbon dioxide (CO2), emitted as a result of fossil fuel combustion, with contributions from cement manufacturers and other sources.
• Methane (CH4), produced through the anaerobic decomposition of waste in landfills, production and distribution of natural gas and petroleum, animal digestion and decomposition of animal wastes, coal production, and incomplete fossil fuel combustion.
• Nitrous oxide (N2O), typically generated as a result of soil cultivation practices, particularly the use of commercial and organic fertilizers, fossil fuel combustion, nitric acid production, and biomass burning.
• Hydrofluorocarbons (HFCs), used primarily as refrigerants.
• Perfluorocarbons (PFCs), originally introduced as alternatives to ozone-depleting substances and typically emitted as byproducts of industrial and manufacturing processes.
• Sulfur hexafluoride (SF6), used primarily in electrical transmission and distribution systems.

Not all GHGs equally affect global climate change. As a result, GHG emissions are commonly quantified in units of their equivalent mass of carbon dioxide (CO2e). CO2e emissions are calculated by applying the appropriate global warming potential (GWP) value to pollutant-specific emissions. GWP ranges from 1 (carbon dioxide) to 22,800 (sulfur hexafluoride). GHGs with a higher GWP have a greater global warming effect on an equivalent mass basis over a specified time frame. For example, over a 100-year time frame, one metric ton (MT) of methane has the same contribution to the greenhouse effect as approximately 25 MT of CO2 and therefore has a GWP of 25.

Greenhouse effect is the warming effect of the Earth's atmosphere. Light energy from the sun that passes through the Earth's atmosphere is absorbed by the Earth's surface and is radiated into the atmosphere as heat energy. The heat energy is then trapped by the atmosphere, creating a situation similar to that which occurs in a car with its windows rolled up. The emission of CO2 and other gases into the atmosphere increases the greenhouse effect and contributes to global warming.

Intergovernmental Panel on Climate Change (IPCC) is a scientific intergovernmental body set up by the World Meteorological Organization and the United Nations Environment Programme to provide decision-makers and others interested in climate change with an objective source of information about climate change.

Net zero GHG emissions refers to the emissions of GHGs such as carbon dioxide, methane, or nitrous oxide by a particular development or human activity being equal to or less than the amount of GHGs that are removed from the atmosphere by that development or human activity (i.e., GHG emissions ≤ GHG reductions).

Troposphere is the zone of the atmosphere characterized by water vapor, weather, winds, and decreasing temperature with increasing altitude.