Solar Calculators
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Solar, EV & Home Energy Calculators & Converters
Solar, EV & Home Energy Calculators & Converters
Solar panel sizing, battery storage, savings estimates, tilt angle, and irradiance calculators for solar shoppers, installers, and homeowners planning an on-grid or off-grid system.
Who This Is For
A solar shopper is usually trying to answer four questions in order: how much energy the house uses, how much sun the roof actually gets, how large the array must be, and whether a battery belongs in the design. These eight calculators are built for that order. They are not a catalog of gadgets. EnterPlanet LLC built them so the same math an installer uses in a first-pass estimate is visible on one screen, with the assumptions you can edit. Read the full guide ↓
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Array size comes from daily or monthly kilowatt-hours, local peak sun hours, a system derate (commonly about 85 percent for planning), and a safety margin (commonly 20 to 25 percent). Peak sun hours are not daylight hours. A site can have twelve hours of daylight and only four and a half peak sun hours because morning and evening light is weaker than midday. The Solar Panel Size Calculator does that conversion. The Solar Irradiance by ZIP Code tool looks up sun hours from National Renewable Energy Laboratory (NREL) solar data — NREL is now officially the National Laboratory of the Rockies. Use those two together before you shop for a 400-watt module.
Tilt and orientation change how much of that irradiance you actually harvest. The Optimal Tilt Angle Calculator estimates a latitude-based angle and then explains what a pitched shingle roof, a flat roof, and a ground mount can actually achieve. Flush-mount residential arrays often take the roof pitch they are given. Flat-roof ballasted racks can set tilt, within wind and ballast limits. Do not treat a calculated optimum as a promise that the roof can hit it.
A grid-tied house that wants evening backup or time-of-use shifting sizes a battery from daily use, backup hours or days, chemistry, and temperature. That is the Solar Battery Storage Calculator. An off-grid cabin or farm sizes the array and the bank together, because the panels have to recharge the bank in the sun hours you actually have, including winter. That is Off-Grid System Sizing. The chemistry facts — depth of discharge, round-trip efficiency, cold-weather loss — appear on both pages in the framing that page is for. Do not copy a home wall-unit size onto an off-grid shed and call it done.
The Charge Controller calculator sizes current and cold-weather voltage for MPPT or PWM once the array voltage and battery voltage are known. Cold mornings raise open-circuit voltage. A controller sized only for a warm datasheet can be overloaded on a bright January morning. Use Advance Mode when you have temperature coefficients; Easy Mode applies a flat cold margin when you do not.
The Solar Savings Calculator estimates bill offset from system size, sun, and your rate. The Carbon Dioxide Offset Calculator estimates avoided grid emissions using regional factors, not a single national slogan number. Neither tool is a tax-credit estimator. Federal and state incentives change and depend on the filer. We do not invent those figures here.
Solar shoppers, installers doing a first pass, engineers checking an assumption, and students learning why derate and peak sun hours exist. If you are new, run Irradiance for your ZIP code, then Panel Size, then Battery Storage or Off-Grid depending on whether you have a utility. Then Charge Controller and Tilt Angle. Then Savings if the question is the bill. The eight cards above are that sequence, not eight unrelated widgets.
What these pages are not: a shade study, a structural roof load letter, a utility interconnection application, or a bid. Tree shade, rafter spanning, and AHJ rules live on site. The calculators tell you what size to discuss. A licensed installer confirms whether that size fits the roof and the code. If a number on a tool looks wrong, use Contact — EnterPlanet LLC would rather correct a formula than leave a closed drawer over the explanation.