Methodology
This page explains where our numbers come from and how we calculate them. Every calculator also shows its formula and inputs next to the result.
Electricity prices
- Average residential price (¢/kWh)
- EIA’s monthly average price for the residential sector in each state: residential revenue divided by residential kWh sales (EIA retail sales data, based on Form EIA-861M). It includes fixed customer charges spread over all kWh sold.
- U.S. average
- EIA’s own U.S. total for the residential sector. We do not average the states ourselves, because states with more customers carry more weight.
- 12-month change
- Latest month compared with the same month one year earlier: (latest − year-ago) ÷ year-ago. Same-month comparison removes seasonal effects.
- Rank
- Position among the 51 jurisdictions (50 states + DC) by latest price, where 1 is the most expensive. Equal prices share a rank.
- Difference vs U.S. average
- (state price − U.S. price) ÷ U.S. price, for the same month.
- Nearest-priced states
- The three jurisdictions whose latest price is closest to the selected state’s price.
- Average monthly use per household (kWh)
- For each of the last 12 months: residential sales (kWh) ÷ number of residential customers, then the average of those 12 values. “Customers” are utility accounts, which is close to, but not exactly, the number of households.
Other prices and inputs
- Typical household electricity use
- EIA annual residential sales ÷ residential customers ÷ 12, for the latest year EIA has published for every state.
- Natural gas price ($/therm)
- EIA residential natural gas price for the latest complete year ($ per thousand cubic feet), divided by the heat content of gas delivered to consumers (Btu per cubic foot ÷ 100, state value where available). We use the annual average because monthly residential gas prices swing strongly with the season. Where EIA has not published a state’s latest annual price, the previous year is used and labeled.
- Gasoline price
- EIA weekly retail price of regular gasoline. EIA publishes state series for only nine states; every other state uses its petroleum region (PADD or sub-PADD) average, and the page says so.
- Solar production
- NLR PVWatts v8 for a 1 kW array in each state’s largest city: standard modules, fixed roof mount, 20° tilt, facing south, 14% system losses, typical-year weather. Production scales linearly with system size.
- Solar export credit
- Each state’s category from the DSIRE (NC Clean Energy Technology Center) map of credit rates for excess generation. Where exports are credited at the retail rate, the default export rate equals the state retail price; where there is no compensation, 0. For other categories there is no single statewide rate, so the default is 0 (a conservative floor) and users should enter their utility’s rate; the calculator also shows payback at 0 and at full retail.
- Heating need
- EIA Residential Energy Consumption Survey (RECS) 2020: average natural gas used for space heating by gas-heated homes in the state, multiplied by an assumed existing-furnace efficiency to get heat delivered, scaled by the user’s heated floor area relative to the state average, and adjusted from 2020 weather to typical weather with NOAA heating degree days (10-year average ÷ 2020). Alaska and Hawaii have no NOAA statewide degree-day series, so no weather adjustment is applied there; DC uses Maryland’s series.
- Cooling capacity
- ENERGY STAR room air conditioner sizing chart (8-ft ceilings, 100–2,499 sq ft) with ENERGY STAR’s adjustments for shade, sun, occupants and kitchens, rounded down to the nearest 1,000 Btu/h.
Calculator formulas
- Appliance running cost
kWh = watts × hours per day × days ÷ 1,000;cost = kWh × rate ($/kWh).- Electric bill
bill = kWh × average price. No separate fixed charge is added because EIA’s average price already includes fixed charges.- EV charging and gas comparison
EV cost per mile = (kWh/100 mi ÷ 100) × rate ÷ charging efficiency;gas cost per mile = gas price ÷ MPG;annual cost = miles per year × cost per mile.- Solar payback
production = kW × kWh/kW;savings = production × (self-consumption × retail rate + (1 − self-consumption) × export rate);net cost = kW × 1,000 × $/W − federal credit;simple payback = net cost ÷ annual savings. The federal credit is 0% for systems completed in 2026 or later and 30% if the “completed in 2025 or earlier” option is chosen.- Heat pump vs gas furnace
heat pump kWh = Btu ÷ (COP × 3,412);furnace therms = Btu ÷ (AFUE × 100,000); break-even electricity price =gas $/therm × COP × 3,412 ÷ (AFUE × 100,000).- Space heater and air conditioner
AC power (W) = Btu/h ÷ EER; then the appliance formula.- Heat pump size
heat loss rate (Btu/h·°F) = annual heat delivered ÷ (heating degree days × 24);heating load = heat loss rate × (65 °F − design temperature). A screening estimate, not an ACCA Manual J calculation.- Water heaters
heat = gallons/day × 8.24 lb/gal × 1.00 Btu/lb·°F × temperature rise × 365(DOE test constants);kWh = heat ÷ (UEF × 3,412);therms = heat ÷ (UEF × 100,000).- Level 2 charger payback
energy = miles × kWh/100 mi ÷ 100; current cost = energy × (public share × public price + home share × home rate ÷ Level 1 efficiency); Level 2 cost = energy × home rate ÷ Level 2 efficiency;payback = installed cost ÷ (current − Level 2).- Solar panel size
kW = annual kWh × share to cover ÷ kWh per kW;panels = kW × 1,000 ÷ panel watts, rounded up.- Solar lease vs buy
- Year t savings = production × (1 − output loss)t−1 × value per kWh × (1 + price change)t−1; buy = Σ savings − net cost; lease = Σ (savings − lease payment × 12 × (1 + escalator)t−1). Undiscounted.
- Home battery backup
energy = Σ (watts × hours) ÷ 1,000 × days;capacity = energy ÷ (usable share × inverter efficiency).- Upgrade loan
payment = P × r ÷ (1 − (1 + r)^−n), r = APR ÷ 12, n = months.
Default assumptions
Defaults are starting points. You can change every input in the calculators.
| Assumption | Default | Basis | Used by |
|---|---|---|---|
| Home charging efficiency Divides the EPA kWh/100 mi rating to allow for real-world charging losses. EPA ratings are measured at the wall and already include typical test losses, so this default is conservative (about 11% higher than the EPA figure); set 100% to use the EPA rating as is. | 90% | Editorial default | EV charging cost, EV vs gas |
| Miles driven per year A round figure close to typical U.S. annual mileage per vehicle. Replace with your own odometer reading. | 12,000 miles | Editorial default | EV charging cost, EV vs gas |
| Comparison gas car fuel economy Combined fuel economy of the gasoline car used for comparison. Use your current car’s EPA combined MPG for a like-for-like comparison. | 27.5 MPG | Editorial default | EV vs gas |
| Solar self-consumption share Share of solar production used directly in the home (valued at the retail rate). The rest is exported to the grid (valued at the export rate). Depends heavily on when you use electricity and on battery storage. | 50% | Editorial default | Solar payback |
| Federal residential clean energy credit (systems completed in 2026 or later) The Section 25D residential clean energy credit does not apply to expenditures for systems completed after December 31, 2025. IRS – Residential Clean Energy Credit. | 0% | Law / regulation | Solar payback |
| Federal residential clean energy credit (systems installed in 2025 or earlier) Applied only when the “installed in 2025 or earlier” option is selected. IRS – Residential Clean Energy Credit. | 30% | Law / regulation | Solar payback |
| Solar system size A typical size for a single-family rooftop system. Size yours from your annual kWh use. | 7 kW | Editorial default | Solar payback |
| Installed solar price (before incentives) Median up-front price paid for host-owned residential systems installed in 2025, before incentives (real 2025 dollars). Cash purchases were lower and loan-financed systems higher; quotes vary widely by installer and state. Berkeley Lab, U.S. Distributed Solar and Storage: 2026 Data Update (Aug 2026). | 3.6 $/W | Published source | Solar payback |
| Heat pump seasonal efficiency (COP) Average units of heat delivered per unit of electricity over the heating season. Efficiency falls in very cold weather; cold-climate models hold up better. Use the rating of the unit you are considering. | 3 COP | Editorial default | Heat pump vs gas furnace |
| Gas furnace efficiency (AFUE) Annual fuel utilization efficiency of a new condensing gas furnace. Older non-condensing furnaces are typically around 80%. | 95% | Editorial default | Heat pump vs gas furnace |
| Efficiency used to estimate heating need from gas use Converts average household gas use for heating (EIA RECS 2020) into heat actually delivered, assuming a typical existing furnace. | 80% | Editorial default | Heat pump vs gas furnace |
| Space heater power A common rating for plug-in electric space heaters on a standard 120 V outlet. Check your heater’s label. | 1,500 W | Editorial default | Space heater & AC running cost |
| Air conditioner cooling capacity Example window unit size. Use the capacity on your unit’s label. | 8,000 Btu/h | Editorial default | Space heater & AC running cost |
| Air conditioner efficiency (EER/CEER) Example efficiency ratio; use the EER or CEER printed on your unit’s EnergyGuide label. | 11 Btu/h per W | Editorial default | Space heater & AC running cost |
| Days of use per season About three months of heating or cooling. Adjust for your climate. | 90 days | Editorial default | Space heater & AC running cost |
| Level 1 (120 V) charging efficiency Slow 120 V charging usually loses a larger share of energy than Level 2. Level 2 uses the home charging efficiency above. | 85% | Editorial default | Level 2 home charger payback |
| Share of charging done at public stations today Example only. Enter your own split. | 50% | Editorial default | Level 2 home charger payback |
| Public charging price Example value, not a market average. Prices vary widely by network, speed and membership; enter what you pay. | 45 ¢/kWh | Editorial default | Level 2 home charger payback |
| Level 2 charger, installed Example value. Installation cost depends mostly on the distance to your panel and whether the panel needs an upgrade; use your quote. | $1,500 | Editorial default | Level 2 home charger payback |
| Solar panel rating A common rating for current residential panels. Use the rating in your quote. | 400 W | Editorial default | Solar panel size |
| Share of electricity use to cover with solar Where exports earn less than retail, covering less than 100% often pays back faster. | 100% | Editorial default | Solar panel size |
| Panel output loss per year Typical warranties assume a small annual decline in output. | 0.5% | Editorial default | Solar lease vs buy |
| Electricity price change per year Applied to the value of solar output each year. Past changes are shown on our electricity rate pages; future prices are uncertain. | 2% | Editorial default | Solar lease vs buy |
| Lease term Use the term in your lease offer. | 20 years | Editorial default | Solar lease vs buy |
| Lease payment (first year) Example value only. Use the payment in your offer. | $120/month | Editorial default | Solar lease vs buy |
| Lease payment escalator Many leases raise the payment each year; use the escalator in your contract (0 if fixed). | 2% | Editorial default | Solar lease vs buy |
| Usable battery capacity (depth of discharge) Share of a battery’s rated capacity you can use. Check the specification sheet. | 90% | Editorial default | Home battery backup sizing |
| Battery inverter efficiency Energy lost converting stored DC power to household AC power. | 90% | Editorial default | Home battery backup sizing |
| Capacity of one battery unit Example unit size used to count units. Enter the capacity of the battery you are considering. | 13.5 kWh | Editorial default | Home battery backup sizing |
| Outdoor design temperature (example) Example only. Your HVAC contractor or local building department can give the heating design temperature for your location. | 5 °F | Editorial default | Heat pump size |
| Hot water use The “medium usage” daily draw used to rate water heaters. Households with more people typically use more. DOE water heater test procedure, 10 CFR 430 Subpart B, Appendix E. | 55 gal/day | Published source | Water heater cost comparison |
| Water temperature rise From 58 °F inlet water to 125 °F delivered, as in the rating test. Colder inlet water in winter raises this. DOE water heater test procedure, 10 CFR 430 Subpart B, Appendix E. | 67 °F | Published source | Water heater cost comparison |
| Electric resistance water heater UEF Federal minimum for a 50-gallon electric storage water heater, medium draw (0.9307 − 0.0002 × 50). DOE energy conservation standards, 10 CFR 430.32(d). | 0.920 UEF | Published source | Water heater cost comparison |
| Gas storage water heater UEF Federal minimum for a 50-gallon gas storage water heater, medium draw (0.6483 − 0.0017 × 50). Condensing models rate higher. DOE energy conservation standards, 10 CFR 430.32(d). | 0.560 UEF | Published source | Water heater cost comparison |
| Heat pump water heater UEF Example rating for a current heat pump water heater; check the UEF on the model you are considering. | 3.5 UEF | Editorial default | Water heater cost comparison |
| Loan amount Example amount. | $20,000 | Editorial default | Home energy upgrade loan |
| Loan APR Example rate only. Use the APR in your loan offer. | 8% | Editorial default | Home energy upgrade loan |
| Loan term Example term. | 10 years | Editorial default | Home energy upgrade loan |
Quality checks
Before any data is published, our pipeline checks that:
- all 50 states, DC and the U.S. total are present, each ending in the same latest month;
- each state has at least 25 consecutive months with no gaps;
- prices fall between 5¢ and 80¢ per kWh and no state moves more than 50% in a single month;
- the data is no more than 6 months old and never older than what is already published.
If any check fails, nothing is published and the previous data stays online. Natural gas, gasoline, solar and EV datasets have equivalent checks (all 51 jurisdictions, plausible ranges, freshness).
State pages are indexed only when every state-specific figure (latest price, 12-month trend, change over 12 months, rank, comparison with the U.S. average, three similar states, at least two worked examples and a one-sentence answer) can be calculated from real data. Pages that miss any element are marked noindex and left out of our sitemaps.
Rounding
We calculate with full precision and round only for display: prices to 0.01¢/kWh, money to the cent (or whole dollars above $1,000) and percentages to one decimal place.
Limitations
State averages hide large differences between utilities, rate plans and seasons. Calculator results are estimates, not quotes or financial advice. For decisions, check your own bills and get quotes from qualified installers.