One of the most common questions we get from rural homeowners exploring solar is: “How big of a system do I actually need?” The answer depends on your location, your appliances, your usage patterns, and whether you’re going fully off-grid or just want backup power. That’s a lot of variables — which is exactly why we built this tool.
Our free Solar System Calculator takes the guesswork out of solar system sizing. Plug in your details, and it gives you a precise recommendation for panel wattage, battery capacity, and inverter size — tailored to your specific situation.
What the Calculator Does
This isn’t a generic “multiply your electric bill by X” estimate. Our calculator uses real data to size your system:
- Location-based solar data: Enter your latitude and longitude for accurate solar irradiance estimates specific to your property. A system in Oklahoma gets very different sun hours than one in Minnesota.
- Array type: Choose between rooftop and ground-mounted arrays — each has different efficiency characteristics and tilt angles.
- Appliance-level planning: Select the specific appliances you need to power. The calculator knows typical wattage draws and duty cycles for common rural household equipment.
- Advanced mode: Override default wattage and duty cycle values for each appliance if you know your exact equipment specs.
- Existing system check: Already have some solar equipment? Enter your current inverter size, battery capacity, and panel wattage — the calculator will tell you if your existing setup is sufficient or what you need to add.
Who Is This For?
The calculator is designed for rural homeowners in any of these situations:
- Going off-grid: You want to disconnect from the utility entirely and need to know exactly what equipment to buy.
- Building a backup system: You want solar + battery to keep essentials running during outages (refrigerator, well pump, internet, lights).
- Expanding an existing system: You already have panels and batteries but aren’t sure if they’re enough — or what to add next.
- Budgeting a project: You need accurate sizing before you start shopping so you don’t overbuy or (worse) underbuy.
- Pairing with a portable power station: Figuring out how many solar panels to pair with your EcoFlow, Jackery, or Bluetti for maximum recharge efficiency.
How to Use It
Step 1: Enter Your Location
Type in your latitude and longitude. Not sure what yours is? Just search “[your town] latitude longitude” — or use your phone’s GPS. The calculator uses this to estimate your average daily sun hours throughout the year.
Step 2: Choose Your Array Type
Select Rooftop if you’re mounting panels on your house or barn, or Ground if you’re installing a ground-mounted array. Ground mounts can be angled more precisely but require more space and mounting hardware.
Step 3: Select Your Appliances
Check off every appliance you want your solar system to power. The calculator pre-loads typical wattage values, but you can switch to Advanced mode to enter exact specs from your equipment nameplates.
Be realistic here — if you’re building a backup system, you probably don’t need to run your clothes dryer on solar. Focus on essentials: refrigeration, water (well pump), internet, lighting, and medical equipment.
Step 4: Check Against Existing Equipment
If you already own solar equipment, enter your current inverter size (kW), battery capacity (kWh), and solar array size (kW). The calculator will compare what you have against what you need and show any gaps.
Common Sizing Mistakes to Avoid
- Underestimating winter production: Solar output drops significantly in winter months. The calculator accounts for this, but many DIY estimates don’t.
- Ignoring surge loads: A well pump might draw 500W running, but 1,500W at startup. Your inverter needs to handle the surge, not just the running watts.
- Forgetting about efficiency losses: Between inverter conversion, battery charging/discharging, and cable losses, you’ll lose 15-25% of your generated power. Build in margin.
- Oversizing for “someday”: It’s tempting to build massive, but start with what you need now. Solar equipment is modular — you can always add panels and batteries later.
👉 Try the Free Solar System Calculator
Have questions about your results or need help interpreting the recommendations? Drop a comment below — we’re happy to help you plan your solar setup.