Free Energy Tools · Powered by EIA, DOE & EPA Data
Solar, Energy & EV
Calculators
19 free tools to convert joules, estimate solar savings, reduce energy bills, compare EV costs, and plan your switch to clean energy.
$150/mo
Avg solar savings
2025
Federal credit cutoff
6-8 yrs
Solar payback
$0.05/mi
EV charging cost
Live US Electricity Prices
Auto-updated monthly from EIA · last refresh: April 25, 2026
🟢 Cheapest States (residential ¢/kWh)
- ND11.64¢
- NE11.79¢
- MO12.17¢
- ID12.63¢
- AR12.73¢
🔴 Most Expensive States
- HI43.00¢
- PACN34.24¢
- CA33.22¢
- ME32.17¢
- CT30.77¢
Source: U.S. Energy Information Administration (EIA), BLS. Updated monthly.
19
Free Tools
50
States + DC
EIA/DOE
Data Sources
0
Data Stored
All Energy Calculators
Organized by category. Click any tool to get started.
Solar
6 toolsPanels from annual kWh, sun hours & roof area
Monthly and annual savings from going solar
Years until panels pay for themselves
Backup battery sizing & cost
Optimize by pitch, orientation & shading
State-specific solar savings data
Home Energy
10 toolsJ, kWh, BTU & watts x time
kWh cost, watts/hour & EIA state rates
Total home appliance costs
Savings from LED bulbs
Annual CO2 emissions
Efficiency score & tips
Monthly bill prediction
Sizing & savings vs gas
Whole-home ROI & credits
Federal & state rebates & credits
Energy & Solar by the Numbers
17.65¢
avg U.S. residential electricity rate/kWh (EIA 2026-02)
23.4%
of U.S. electricity from renewables (EIA, 2025)
10,500
kWh avg annual household usage (EIA, 2025)
$0.05
/kWh home EV charging vs $0.15/mile gas (DOE)
JouleIO is the most comprehensive free energy calculator suite available online. With 19 calculators covering joule conversion, solar energy, electricity costs, electric vehicles, wind power, and carbon footprint, JouleIO eliminates the need for multiple apps or paid energy audit services. Every calculation runs instantly in your browser using real-world data from the EIA, DOE, SEIA, and EPA.
Whether you're estimating solar savings, calculating electricity costs, comparing EV vs gas, or running a home energy audit, JouleIO delivers accurate results in seconds. For mortgage tools, visit Amortio. For tax planning, see LevyIO. For construction estimates, try HammerIO.
From the Blog
View all articles →Solar Panel Guide: Everything You Need to Know
Costs, savings, installation, and whether solar is right for you.
EVEV Charging Guide: Home, Public & Costs
Level 1 vs 2 vs 3 charging, home setup, and cost comparison.
Energy SavingsHow to Reduce Your Electricity Bill
Practical tips to cut energy costs by 20-40% this year.
Frequently Asked Questions
What is JouleIO?
JouleIO is a free collection of 19 solar, energy, and EV calculators. Convert joules, estimate solar savings, calculate electricity costs, compare EV charging options, and measure your carbon footprint — all in your browser.
How accurate are the energy estimates?
Our calculators use EIA electricity rates, SEIA solar data, and EPA emission factors. Results are planning estimates — get professional quotes for exact costs.
Is my data private?
Yes. All calculations happen locally in your browser. Your energy usage and other data never leave your device.
Which calculator should I start with?
Try the Solar Savings Calculator to see if solar makes sense, or the Electric Bill Estimator to understand your current costs.