SolarToolsSolar & energy calculators
that do the real math.
51 professional calculators for solar sizing, battery ROI, EV charging, heat pumps, and energy auditing. Built for homeowners, businesses, and renewable energy professionals.
Most popular calculators
Solar Panel Sizing Calculator
Calculate how many panels you need based on energy usage, location, and panel wattage.
Open calculator →Solar Payback Calculator
How many years until your solar panels pay for themselves? State-by-state estimates.
Open calculator →Battery Storage ROI Calculator
Payback period for home battery systems based on your rates, usage, and battery cost.
Open calculator →EV Charging Cost Calculator
Compare charging costs vs petrol or diesel, with per-mile and annual savings.
Open calculator →Solar Planning
Size your system, estimate production, and plan your solar installation.
Solar Panel Sizing Calculator
Calculate how many panels you need based on energy usage, location, and panel wattage.
Open calculator →Solar Savings Calculator
25-year savings projection with inflation, degradation, and net metering.
Open calculator →Solar Panel Tilt & Angle Calculator
Find the optimal panel tilt and azimuth for your latitude and seasonal needs.
Open calculator →Solar Inverter Sizing Calculator
Size your solar inverter correctly — string vs microinverter, DC/AC ratio, and clipping losses.
Open calculator →Voltage Drop Calculator (Solar Wire Sizing)
Size your solar DC wiring correctly — prevent voltage drop and energy loss.
Open calculator →Roof Solar Potential Calculator
Evaluate your roof's solar potential — orientation, tilt, shading, and usable area.
Open calculator →Battery & Storage
Calculate battery capacity, ROI, and backup power for your energy storage needs.
Battery Storage ROI Calculator
Payback period for home battery systems based on your rates, usage, and battery cost.
Open calculator →Off-Grid System Designer
Size a complete off-grid solar + battery + generator system for true energy independence.
Open calculator →Generator Sizing Calculator
Pick the right generator size for backup power — accounts for motor starting surges.
Open calculator →Battery Capacity Calculator (Off-Grid)
How much battery capacity do you need for off-grid or backup power?
Open calculator →Residential Wind Turbine Calculator
Size a small wind turbine for your property — production, cost, and payback.
Open calculator →Electrical & Wiring
Size inverters, cables, generators, and understand your electrical system.
Generator Sizing Calculator
Pick the right generator size for backup power — accounts for motor starting surges.
Open calculator →Solar Inverter Sizing Calculator
Size your solar inverter correctly — string vs microinverter, DC/AC ratio, and clipping losses.
Open calculator →Voltage Drop Calculator (Solar Wire Sizing)
Size your solar DC wiring correctly — prevent voltage drop and energy loss.
Open calculator →Heat Pump Sizing Calculator
Size your heat pump correctly by home size, climate, and insulation quality.
Open calculator →Solar String Design Calculator
Calculate how many panels per string and how many strings for your inverter.
Open calculator →Power Factor Calculator
Calculate power factor, apparent power, and correction capacitor size for your facility.
Open calculator →Financial & Savings
Calculate payback, ROI, tax incentives, and financing options for solar and energy upgrades.
2026 Solar Incentive & Net Cost Calculator
Calculate your true net solar cost using state rebates, SRECs, and any incentives you qualify for.
Open calculator →Section 12B Solar Tax Calculator (South Africa)
Calculate your SARS Section 12B/12BA accelerated depreciation for solar in South Africa.
Open calculator →Solar Loan vs Cash Purchase Calculator
Compare financed vs cash-paid solar over 25 years. APR, opportunity cost, and break-even.
Open calculator →Solar Lease vs Buy Calculator
Compare leasing vs buying solar panels — 20-year total cost and savings.
Open calculator →EV & Solar Charging
Size solar for your EV, match your charger to panel output, calculate V2H backup, and compare solar-charged EV vs petrol.
EV Charging Cost Calculator
Compare charging costs vs petrol or diesel, with per-mile and annual savings.
Open calculator →EV Range Calculator
Realistic range estimate accounting for speed, temperature, terrain, and driving style.
Open calculator →EV Total Cost of Ownership Calculator
Real 5-year cost: purchase, fuel, maintenance, insurance, depreciation for EV vs petrol.
Open calculator →Home EV Charger Installation Cost Estimator
What will it cost to install a Level 2 EV charger at home? Panel, wiring, distance, permits.
Open calculator →EV Road Trip Planner
Plan your EV road trip — charging stops, drive time, and total trip duration.
Open calculator →EV Solar Charging Calculator
How many solar panels does it take to charge your EV? Enter daily driving distance and panel specs.
Open calculator →Solar + EV Combined System Sizing Calculator
Size a single solar system that powers both your home and your EV. One roof, one system, two loads.
Open calculator →EV Battery as Home Backup (V2H/V2G) Calculator
Your EV has a 60-100 kWh battery. How long can it power your home during an outage or loadshedding?
Open calculator →EV vs Gas Payback with Solar Calculator
True EV payback when you charge with solar vs grid vs petrol. The solar-charged EV often wins by $10k+.
Open calculator →Home Charger Sizing with Solar Calculator
Match your EV charger power to your solar output. Level 1, Level 2 (7.2kW), or Level 2 (11.5kW)?
Open calculator →Home Efficiency
Audit your energy use, reduce bills, and find savings on appliances and heating.
Appliance Wattage Lookup
Searchable database of common household appliance wattages with daily usage and category filters.
Open calculator →Time-of-Use Rate Optimizer
When to run appliances based on peak and off-peak electricity pricing.
Open calculator →Heat Pump Payback Calculator
Compare heat pump vs gas or oil heating costs and find the payback period.
Open calculator →Electricity Bill Estimator
Estimate your monthly electricity bill based on appliance usage and your local rate.
Open calculator →Energy Audit Calculator
Identify where your electricity spend goes, room by room, load by load.
Open calculator →CO₂ & Carbon Savings Calculator
How much CO₂ do you save with solar, an EV, or a heat pump? See your impact in tons and trees.
Open calculator →Commercial Energy
Demand charges, power factor, microgrids, and solar carports for businesses.
Demand Charge Calculator (Commercial)
Calculate your commercial electricity demand charges and find savings opportunities.
Open calculator →Microgrid Sizing Calculator
Size a solar + battery + generator microgrid for commercial or community facilities.
Open calculator →Solar Carport Calculator
Estimate costs, production, and ROI for commercial solar carports and canopies.
Open calculator →Transparent math
Every result shows the formula and inputs. Nothing hidden behind a "Get Quote" wall.
Runs in your browser
No server calls, no analytics on inputs, no account. Your numbers never leave your device.
Every page teaches
Each calculator includes a how-to, a deep dive, and an FAQ so you can sanity-check every number.
Solar by location
Pre-loaded rates, sun hours, net metering policies, and incentives for 68 regions across 6 countries.
Head-to-head comparisons
Spec-by-spec breakdowns of the most popular batteries, EVs, and heating systems. No marketing fluff.
Tesla Powerwall 3 vs Enphase IQ Battery 5P
The two most popular home batteries compared: capacity, efficiency, price, and which to choose.
Tesla Powerwall 3 vs LG RESU Prime
Tesla's all-in-one vs LG's high-efficiency battery — which is right for your home?
Heat Pump vs Gas Furnace: Which Saves You More?
Operating cost, install cost, comfort, and 10-year economics compared for typical US homes.
EV vs Petrol Car: True 5-Year Cost of Ownership
Purchase price, fuel, maintenance, insurance, and depreciation compared over 5 years.
Latest from the blog
Long-form explainers on solar, batteries, EV charging, and the economics of home energy.
How Many Solar Panels Do I Need? A Complete Sizing Guide
Everything you need to know about sizing a residential solar system: energy usage, peak sun hours, panel wattage, losses, and real-world examples.
Understanding Time-of-Use Electricity Rates: Save Money by Shifting Load
How TOU pricing works, why utilities use it, and how much you can save by shifting dishwasher, laundry, EV charging, and water heating to off-peak hours.
Is a Home Battery Worth It? Breaking Down the ROI Math
The honest economics of home battery storage. Why most batteries don't pay back on pure economics, and the three cases where they actually do.
Not sure where to start?
Run the Energy Audit first. It tells you where your kilowatt-hours actually go, and points you to the right calculator next.
Start the energy audit