Browse by category
Sizing and layout for photovoltaic systems: system kW from consumption, expected kWh production, roof area and module count, row…
Load audits, battery bank capacity, depth of discharge, backup autonomy, recharge time and generator runtime for off-grid cabins…
The financial and energetic case for solar: payback period, levelized cost of energy, net metering credit value, the federal tax…
Power and yield calculations for wind turbines and micro-hydro sites: the cube law, rotor swept area, capacity factor and annual…
Fuel energy content and heating consumption from degree days, water-heating cost, and the payback math for insulation, window and…
Emission-factor and stoichiometric calculations for household, driving, flying, electricity, fuel-combustion, diet and…
Rainwater harvesting yield and cistern sizing, stormwater peak flow and runoff volume by the Rational Method and NRCS curve…
Environmental monitoring math: EPA Air Quality Index from pollutant concentrations, gas concentration unit conversion, and the…
Most used in energy, solar, sustainability & environment
- Solar System Size (kW) CalculatorNREL PVWatts sizing methodEnter the kWh figure from your electric bill and this calculator returns the DC array size in kilowatts needed to hit your…
- Solar Panel Output (kWh) CalculatorNREL PVWatts loss modelEnter your array's DC rating, the peak sun hours your site receives, and the losses between the module glass and the meter, and…
- Solar Panel Count & Roof Area CalculatorIRC R324 / IFC 1204 access pathwaysGive this calculator a target system size and the module you intend to use, and it returns the number of modules, the total…
- Off-Grid Daily Load Audit (Watt-Hours) CalculatorEvery off-grid, RV and marine solar design starts with one number: the watt-hours your loads consume in a day. This calculator…
- Off-Grid Battery Bank Amp-Hour CalculatorIEEE 1013 sizing methodThis calculator turns a daily watt-hour load into the amp-hour capacity of an off-grid battery bank, then works out how many…
- Home Battery Backup Sizing CalculatorNEC 2023 Article 706Tell this calculator how much energy your critical loads consume in a day, how long you need to ride through an outage, and how…
- Solar Panel Payback Period CalculatorDiscounted cash flow analysisThis calculator returns the year your solar system finishes paying for itself, on two different definitions. Simple payback…
- Solar LCOE CalculatorNREL / IEA levelized cost of energy definitionLevelized cost of energy converts a generation asset into a single price per kilowatt-hour: the constant revenue per kWh that…
- Net Metering Savings CalculatorNet energy metering / net billing tariff arithmeticThis calculator tells you what a rooftop solar array is actually worth on your electric bill once your utility stops paying…
- Federal Solar Tax Credit (ITC) CalculatorIRS Form 5695 / 26 U.S.C. §25DThis calculator applies a solar tax credit to the right base, in the right order, and shows what you can actually use this…
- Wind Turbine Power Output CalculatorWind power equation P = ½ρAv³Cp; ISA atmosphere for air densityThis calculator applies the wind power equation — half the air density times swept area times the cube of wind speed, scaled by…
- Wind Capacity Factor CalculatorCapacity factor definition; Weibull/Rayleigh wind speed distributionCapacity factor is the single number that tells you how hard a generating asset actually works: energy delivered divided by the…