Solar math you can actually trust.
Five precise calculators for home solar and off-grid systems. No email walls, no installer spam, no data selling — just the numbers.
Pick your calculator
Each tool runs the real engineering math and links to the next step in your build.
Sizing & savings
Solar savings & payback
Cost, payback, IRR, 25-year savings & cashflow chart — plus net-metering, time-of-use rates, battery ROI, cash-vs-loan-vs-lease and roof/shading. Region-aware, free.
Calculate savings →System size & panel count
Turn your kWh usage and sun hours into the kW system size and the number of panels you actually need.
Size my system → NewHome & office sizing
Size a building's solar system and optional battery backup — from your appliances or just your monthly bill.
Size my building →Off-grid battery bank
Size your battery bank in Ah and kWh for off-grid, RV, van or cabin builds — by chemistry, voltage and days of autonomy.
Size my battery →Solar output (kWh)
Estimate daily and yearly energy production from your panel wattage, sun hours and real-world system losses.
Estimate output →Inverter sizing
Add up your running and surge loads to find the continuous and peak inverter rating your system requires.
Size my inverter →Load calculator
List your appliances to total your daily watt-hours and a recommended system size — then send it straight to the sizing tools.
Add up my load →Panel comparison
Put two panels side by side — 25-year output, cost per watt and lifetime cost per kWh — and see which is the better value.
Compare panels →Home electrification
See how adding an EV and a heat pump grows your usage — and the solar needed to power an all-electric home.
Plan electrification →Carbon offset
How much CO₂ your system avoids — in trees, cars and flights — over a year and across 25 years.
See my impact → NewRoof area to panels
Start from your roof size: how many panels fit, the kW they add up to, and what they generate.
Measure my roof → NewSolar panels for AC
How many panels to run a 1, 1.5 or 2-ton air conditioner — plus the battery needed for night cooling.
Run my AC on solar →Wiring & components
Wire & cable gauge
Get the safe cable size in AWG and mm² from your current, run length and voltage. Undersized wire is a fire risk.
Size my wire → NewVoltage drop
Check the exact voltage drop for a wire you already have, with a clear pass/fail against safe limits.
Check drop → NewCharge controller sizing
Size your MPPT or PWM controller in amps from your array wattage and battery voltage, with the right safety margin.
Size my controller → NewSeries vs parallel wiring
See how series, parallel, or mixed wiring changes total voltage and capacity — with a live, shareable diagram.
Visualize wiring → NewRV, van & boat solar
Toggle your appliances and size the whole system — battery, solar and inverter — for a van, RV, boat or tiny home at once.
Build my system →Tilt angle
Get the optimal year-round panel angle from your latitude, plus seasonal angles for adjustable mounts.
Find my tilt →String sizing
How many panels you can safely wire in series within your inverter's voltage window — temperature-corrected.
Size my string →Backup, EV & utilities
Battery backup runtime
Find out how many hours your battery bank will keep your loads running during an outage or off-grid night.
Check runtime → NewGenerator sizing
Size a backup generator from your appliances, accounting for the surge that motors draw on startup.
Size my generator → NewEV charging from solar
See how much solar covers your daily driving, the energy your EV uses, and how long a charge takes.
Calculate EV solar → NewPool heater sizing
Size a pool heat pump by volume, temperature rise and surface area — with the electrical draw it adds.
Size my heater → NewWell pump sizing
Find the pump horsepower and wattage you need from flow rate and total head, plus the solar to run it.
Size my pump → NewMini-split & AC sizing
Size the cooling capacity a room needs in BTU and tons, plus the electrical draw and solar to power it.
Size my mini-split → NewOff-grid & hybrid system
Size the array, battery bank (with days of autonomy) and inverter for a standalone or hybrid system — cabins, farms, or outage-prone areas.
Size off-grid →Generator vs solar battery
Compare the 10-year cost of a backup generator against a solar battery — fuel and maintenance vs daily savings.
Compare backup → NewHome battery payback
Is a battery worth it? Annual value of every stored kWh, payback vs lifespan, and an honest verdict.
Check battery ROI → NewDiesel vs solar
The true cost per kWh of generator power — fuel plus maintenance — against a solar hybrid.
Compare running costs → NewSolar water heating
Thermal solar water heater vs extra PV panels for your geyser — energy, savings and payback for both.
Compare both routes →Unit converters — quick solar & electrical conversions
Watts to amps
Convert power to current for DC, AC single-phase and three-phase, with voltage and power factor.
Convert W → A →Ah to kWh
Turn battery amp-hours into kilowatt-hours by voltage, with watt-hours and usable capacity.
Convert Ah → kWh →AWG to mm²
Wire gauge conversion with diameter, circular mils and a typical copper ampacity.
Convert gauge →BTU to kW
Cooling and heating capacity between BTU/hr, kilowatts, tons and watts.
Convert BTU → kW →kW to kVA
Real to apparent power using power factor — the number that sizes generators.
Convert kW → kVA →HP to kW
Horsepower to kilowatts and watts for pumps, motors and generators.
Convert HP → kW →kWh to MJ
Energy units — kilowatt-hours, megajoules, BTU, therms and kilocalories.
Convert energy →Ohm’s law
Enter any two of volts, amps, ohms and watts to solve the other two.
Solve V·I·R·P →Solar by country — localized subsidies & tariffs
Solar calculator USA
Savings & payback by state, with the honest 2026 federal-credit reality (residential 30% ITC ended for owners), net-metering options incl. NEM 3.0, and battery economics.
Calculate by state → USANEM 3.0 battery calculator
California net billing: why solar-only barely saves, and how a battery shifting power into the 4–9 PM peak changes the math. Solar-only vs solar+battery payback.
Compare under NEM 3.0 →Solar calculator India
PM Surya Ghar subsidy (₹30,000–₹78,000) applied automatically, plus net cost, EMI on the govt loan, units/day and your free-electricity date.
Check PM Surya Ghar → IndiaOn-grid solar (India)
Grid-tied with net metering, no battery — the cheapest, most common setup. Subsidy, bill offset, net cost and payback.
Size on-grid → IndiaSolar loan EMI calculator
Real monthly EMI under PM Surya Ghar — cost minus subsidy at your rate and tenure, with honest subsidy timing and EMI-vs-savings. No "₹0 down" teaser.
Work out my EMI → IndiaPM-KUSUM solar pump
For farmers: the central (30%/50%) and state subsidy on an agricultural solar pump, your out-of-pocket share, and diesel saved.
Check KUSUM subsidy → IndiaCommercial solar (India)
For business: ROI, payback, the accelerated-depreciation tax benefit (40% year 1), and buy (CAPEX) vs RESCO/PPA (OPEX) comparison.
Calculate commercial ROI →Every state and union territory with its local tariff, sun-hours and net metering. Full directory →
Solar calculator Pakistan
2026 NEPRA net-billing rules, the new buyback rate and high grid tariffs — with why self-consumption and batteries now matter most.
Calculate savings → PakistanNEPRA net billing calculator
The Prosumer Regulations 2026 (SRO 251) explained: legacy vs new rates, the 80% transformer cap, and your bill under net billing — for any DISCO.
Model the new rules →How it works
From rough idea to a build-ready spec in three steps.
Enter your numbers
Your bill, usage or appliance list. No address or email required to get a result.
Get instant math
Industry-standard formulas run live in your browser — see exactly how every number is derived.
Move to the next tool
Each calculator hands its results to the next, so your sizing stays consistent end to end.
Why we built this
Most solar calculators are lead-generation tools. They keep the math shallow so you'll hand over your phone number and get passed to installers.
ProSolarCalc is different. The calculator is the product — not the bait.
- ✓Unbiased. We don't sell panels, so the recommended size isn't padded to sell you hardware.
- ✓Private. No email wall, no contact form, no reselling your data to installers.
- ✓Transparent. Every calculator shows its formula so you can check the work.
- ✓Current. Updated for 2026 incentive rules that most tools still get wrong.
Run a blog or installer site? Every calculator here is free to embed on your own website with one line of HTML.