Home energy planning toolkit

Free Solar, EV & Home Energy Calculators

EV charging time calculatorSolar panel sizing calculatorBattery runtime calculatorHome backup power calculator

Plan solar panels, EV charging, battery backup, generators, and home energy upgrades with simple online calculators. Calculate charging time, solar payback, battery runtime, generator size, net metering savings, heat pump costs, and more.

Open calculatorCalculate EV charging time
01EV charging time calculator02Solar panel calculator03Battery runtime calculator04Home battery backup calculator

Calculator directory

Choose the right EV, solar, and battery calculator

Use these energy calculators to compare EV charging time, solar panel size, battery runtime, and home backup power before choosing chargers, panels, batteries, or portable power stations.

Core calculators for energy planning

More calculators for trips, payback, sizing, and ownership
EV charging time calculatorEstimate how long it takes to charge an electric car from one state of charge to another, including wall energy and charging losses.EVSolar panel calculatorSize a solar array from daily kWh use, peak sun hours, system losses, and selected panel wattage.SolarBattery runtime calculatorCheck how long a battery, UPS, or portable power station can run appliances from capacity and load.BatteryHome battery backup calculatorModel outage coverage from critical loads, usable battery capacity, solar production, and target backup days.Backup

More energy calculators

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EV road trip calculatorEstimate stops, charging time, and drive time from route distance, EV range, battery capacity, departure SOC, reserve SOC, target stop SOC and DC charger power.EVSolar payback calculatorApply the 30% federal ITC, model 0.5%/year panel degradation and 3%/year rate inflation, and see year-by-year cumulative savings until the system breaks even.SolarNet metering calculatorCompare a solar bill under traditional 1:1 net metering vs export-only credits (e.g. CA NEM 3.0). Get monthly net cost, exported kWh, self-consumption ratio, and annualized totals.SolarHeat pump vs gas calculatorConvert your annual heating demand to kWh and therms with COP and AFUE, then compare yearly fuel cost and CO₂. Uses EPA grid average 0.39 kg CO₂/kWh and 5.3 kg CO₂/therm.EnergyGenerator sizing calculatorList your running watts and the largest motor (well pump, AC compressor, fridge), apply LRA-based starting surge, and add a safety factor for fuel headroom and altitude derating.BackupSolar lease vs buy calculatorModel cash purchase (with 30% ITC) versus a 25-year lease with annual escalator. Inputs: system cost, lease payment year 1, escalator %, annual production, retail rate.SolarSolar panel tilt calculatorGet the year-round optimal tilt (≈ latitude), summer tilt (latitude − 15°) and winter tilt (latitude + 15°), plus expected production gain from seasonal adjustment.SolarSolar inverter sizing calculatorNREL and SEIA recommend a DC:AC ratio of 1.15–1.30. Higher ratios cost less per AC watt but cause midday clipping. Find the sweet spot for your location.SolarWind turbine calculatorEstimate annual kWh from rotor swept area, average wind speed, air density, capacity factor and turbine efficiency. Uses the Weibull-corrected power equation.WindEV total cost of ownership calculatorSum purchase price (minus federal tax credit), fuel/electricity, insurance, maintenance and registration over 5 years. Default electricity 4.0 mi/kWh, gas 28 mpg.EV

Formula notes

Transparent formulas behind each calculator

EV charging time formula

wall kWh = battery kWh x SOC change / charging efficiency

Charging time divides wall energy by charger power. Cost multiplies wall energy by electricity price.

Battery runtime formula

runtime hours = capacity Wh x usable percent x inverter efficiency / load W

Standby draw is included because small always-on loads matter during long outages.

Solar panel sizing formula

solar kW = daily kWh / (peak sun hours x performance factor)

Panel count rounds up from array watts divided by the selected solar panel wattage.

Battery backup formula

coverage days = usable battery kWh / max(0, daily load kWh - daily solar kWh)

Solar production uses a conservative real-world performance factor for inverter and weather losses.

Planning scenarios

Useful before choosing chargers, panels, batteries, or backup power

Compare Level 1, Level 2, and DC fast charging assumptions before buying an EV charger.

Estimate whether a portable power station can run a refrigerator, router, CPAP, or workstation.

Size a rooftop solar array and battery bank before requesting installer quotes.

Model blackout coverage before buying batteries, panels, inverters, or generator backup.

FAQ

Common questions

What information do I need to use these calculators?

Most estimates only need values you can find on an EV, charger, solar panel, battery label, or electricity bill: capacity, power, load, price, peak sun hours, and efficiency.

Why is EV charging time not just battery energy divided by charger power?

Charging has conversion losses, and real vehicles often taper charging near high state of charge. This calculator models the main loss factor and is best for planning estimates.

How accurate is the solar panel calculator?

It is useful for early sizing. Real output depends on roof angle, shade, weather, inverter clipping, utility rules, and local permitting.

Can I use the results before buying equipment?

Yes. The calculators are designed for early planning and comparison. Always check product manuals, installer recommendations, utility rules, and local electrical codes before purchasing or installing equipment.