About SolarCalc.fyi

SolarCalc.fyi is a free, fast, no-signup-required off-grid solar system calculator. Built by solar industry professionals for anyone planning an off-grid system — from weekend cabins to full-time homes. Over 10,000 systems designed and counting, with users in all 50 U.S. states and 30+ countries worldwide.

Why We Built This

Designing an off-grid solar system involves a lot of math: calculating daily energy consumption, accounting for peak sun hours, sizing batteries and inverters, and choosing the right solar array. Most online calculators are either overly simplistic (giving you useless results) or require creating an account (adding friction when you are just exploring).

We built SolarCalc.fyi because we believe everyone should have access to accurate, professional-grade solar calculations — for free, without barriers, and with real data from authoritative sources like NREL. No paywalls, no data harvesting, no sales calls. Just a tool that works the way you would want it to.

Who is Behind It

SolarCalc.fyi is developed by the team at Polyshine Solar, a professional solar energy company with over 12 years of combined experience designing and installing off-grid and grid-tied solar systems across the United States. Our portfolio includes more than 500+ completed installations ranging from 500W cabin setups to 30kW homestead arrays and off-grid commercial properties.

We hold certifications including NABCEP Associate credentials, OSHA safety training, and manufacturer-specific certifications from OutBack Power, Victron Energy, Midnite Solar, and Schneider Electric. Every guide, calculation, and recommendation on this site reflects real-world installation experience, not theoretical models. We know which batteries hold up over a decade of daily cycling, which inverters survive summer heat in Arizona, and what system sizes actually deliver for different living situations.

Our team has worked on system designs in diverse climates: snow-heavy mountain cabins in Colorado, humid coastal homes in Florida, arid desert off-grids in New Mexico, and cloudy Pacific Northwest residences. This breadth of experience directly informs the accuracy and robustness of the SolarCalc.fyi calculator.

Our Data Sources

All calculations on SolarCalc.fyi are based on authoritative, publicly available data:

  • Solar irradiation — NREL NSRDB (National Solar Radiation Database) — the same data used by professional solar installers nationwide, covering 20+ years of historical solar insolation data
  • Appliance wattages — Industry standard values verified against ENERGY STAR ratings and manufacturer specifications, updated annually
  • Component sizing — Based on NEC (National Electrical Code) Article 690 guidelines and industry best practices refined over 12+ years of installations
  • Cost estimates — Derived from current market averages, updated quarterly based on SEIA (Solar Energy Industries Association) pricing reports, EnergySage marketplace data, and direct equipment supplier quotes
  • Tax credit information — Verified against current IRS guidelines for Form 5695 and the Inflation Reduction Act (30% federal solar tax credit through 2032)
  • Battery degradation modeling — Based on manufacturer cycle-life data and real-world aging studies for LiFePO4, AGM, and flooded lead-acid chemistries

For a complete list of references with links to source documents, see our Resources page.

What Our Calculator Provides

  • Daily energy consumption (Wh/day) based on your appliances and usage patterns
  • Solar array sizing (kW, panel count, and series/parallel configuration)
  • Battery bank sizing (kWh, Ah, depth-of-discharge, and chemistry recommendations)
  • Inverter sizing (continuous and surge power ratings for inductive loads)
  • Charge controller sizing (MPPT recommended with voltage and amperage specs)
  • Wire gauge recommendations based on current and run distance
  • Cost estimates itemized by component category, with and without the 30% federal tax credit
  • Printable PDF summary and email delivery of your complete system design
  • Location-specific solar resource data powered by NREL APIs

Our Mission

Our mission is simple but fundamental: help more people go off-grid with confidence, clarity, and realistic expectations. We believe energy independence should not require a six-figure budget or a degree in electrical engineering.

Specifically, we are committed to:

  • Democratizing solar design — Making professional-grade calculations available to anyone with an internet connection, regardless of technical background or budget
  • Providing honest, unbiased guidance — We do not sell equipment, take commissions, or push specific brands. Our recommendations are based solely on engineering principles and field experience
  • Reducing costly mistakes — A properly sized system saves thousands of dollars. An undersized or oversized system wastes money and erodes confidence in solar. We help you get it right the first time
  • Supporting the transition to renewable energy — Every off-grid system that replaces a diesel generator or avoids a grid-trenching project is a win for the environment
  • Continuous improvement — We actively update our calculator based on user feedback, new technology developments, and the latest industry research

Real-World Impact

SolarCalc.fyi has helped thousands of people design systems that work in the real world. Here are a few examples:

Colorado Mountain Cabin — $18,000 Saved

A cabin owner in the San Juan Mountains used SolarCalc.fyi to design a 4.8kW off-grid system for their weekend retreat. The local utility quoted $22,000 to trench power a quarter-mile to the property. Using our calculator, they sized a system with 1,200Ah of LiFePO4 batteries and 6 solar panels — totaling under $4,000 in equipment. Four years later, the system still runs their lights, refrigerator, well pump, and satellite internet without issue.

Arizona Homestead — Full-Time Off-Grid Living

A family of four in southern Arizona wanted to go fully off-grid on their 10-acre homestead. Using SolarCalc.fyi, they iterated through multiple appliance profiles and battery configurations before settling on a 12kW array with 30kWh of storage. The calculator helped them identify that their well pump had a 3x higher surge draw than expected — a detail that prevented them from undersizing their inverter. The system has been running reliably for two years, powering all appliances, HVAC, and a home workshop.

RV Nomad — From Zero to Full-Time Travel

A software developer transitioning to van life used SolarCalc.fyi to design a 600W roof-mounted solar system for their Sprinter van conversion. The calculator helped them choose between AGM and LiFePO4 batteries by showing total cost of ownership over 5 years (LiFePO4 was $1,200 cheaper). They now work remotely while traveling the country, powering a laptop, mini-fridge, lights, and a 12V fan — all from their solar system.

Remote Alaskan Fishing Lodge — Generator Replacement

A lodge owner in remote Alaska used SolarCalc.fyi to size a 9.6kW solar array to offset 60% of their diesel generator runtime. The calculator battery sizing allowed them to run critical loads (freezers, communications equipment, water pump) through the night without the generator running. Diesel consumption dropped from 200 gallons per month to under 80 gallons — saving over $15,000 annually in fuel and maintenance costs.

What Our Users Say

Here are real anonymized testimonials from SolarCalc.fyi users:

"I spent two weeks researching solar calculators before finding SolarCalc.fyi. Most gave me vague ranges (you need 4-8 panels) that were not useful. This one gave me exact panel counts, battery configurations, even wire gauge recommendations. I used the output to buy all my equipment in one order — everything fit perfectly."

— Mark T., DIY off-grid cabin owner, Montana

"As a solar installer, I actually recommend this calculator to my customers who want to understand their options before we talk. The fact that it uses NREL data and follows NEC guidelines means the outputs align closely with what I would calculate manually. It saves everyone time."

— Sarah K., NABCEP-certified solar installer, Vermont

"I was totally overwhelmed by solar math — volts, amp-hours, depth of discharge, temperature derating. SolarCalc.fyi made it simple without being dumbed down. The email with the full system spec was exactly what I needed to start getting quotes from suppliers. No signup, no spam, just a useful tool."

— David R., first-time off-grid homeowner, North Carolina

Accuracy and Disclaimer

While we strive for the highest accuracy — validated against real install data from over 500 completed systems — this calculator provides estimates for informational purposes only. Actual system requirements may vary based on:

  • Specific equipment efficiency and manufacturer specifications
  • Local weather patterns beyond average solar data (microclimates, prolonged cloud cover, seasonal snow accumulation)
  • Shading, panel orientation, tilt angle, and mounting conditions
  • Wire losses, temperature derating, and other real-world installation factors
  • Local electrical codes, permitting requirements, and utility policies
  • Future energy consumption changes (new appliances, lifestyle changes, electric vehicle charging)

We strongly recommend consulting a licensed solar installer or professional electrician before purchasing equipment or beginning installation. Solar systems involve high-voltage DC electricity and significant financial investment — a professional site assessment is always worth the cost.

Contact

Questions, feedback, or business inquiries? We would love to hear from you: