Stop guessing. Get the exact solar panel count, battery size, and inverter rating your home or off-grid project actually needs—using the same math certified installers use.
⚡ Professional Solar Sizing Calculator
Complete sizing for Solar Panels • Battery Storage • Inverter • Charge Controller • Wiring
Quick Presets
POPULARSystem Summary
—Equipment Breakdown
| Component | Specification | Quantity | Notes |
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| Click Calculate to see details | |||
Getting solar wrong is expensive. Oversize by 20% and you’ve wasted $3,000–$5,000 on panels you’ll never fully use. Undersize by 20% and your utility bill barely moves. Both mistakes happen constantly because most free calculators reduce everything to one input: daily kWh. That’s not enough.
A proper solar sizing calculator accounts for 5 variables working together: daily energy consumption, your location’s peak sun hours, real efficiency losses, backup duration, and equipment compatibility. Each one changes the output. Each one gets its own section here.
This guide is built on data from 10,000+ real installations across 6 continents, cross-referenced with NREL, NEC Article 690, and IEC 62548 standards as of June 2026. Every section stands on its own—jump to what you need.
How Does a Professional Solar Sizing Calculator Actually Work?
A professional solar sizing calculator takes your daily energy needs, divides by your location’s peak sun hours, then applies derating factors for temperature, shading, cable resistance, and inverter efficiency. It outputs panel count, battery capacity, and inverter rating in one pass—accounting for losses a basic calculator skips entirely.
Your electricity bill gives you one number: total kWh consumed last month. That’s a good starting point. But the solar array size you actually need depends on when you use that energy, how much you need available during an outage, and how much your equipment loses to heat and wiring resistance before it reaches your outlets.
Put a 10 kW array in Dallas and it generates roughly 55 kWh on a good June day. Put the same array in Seattle and you get about 35 kWh—a 57% gap from location alone. Add a rooftop that runs 15°C hotter than ambient and another 8% disappears. The solar power sizing calculator stacks all these factors together so the output reflects what your system will actually produce.
The Core Solar Sizing Formula
When you input 15 kWh daily usage, the calculator applies derating factors for cable losses (typically 2–3%), temperature effects (0.4% per degree above 25°C), inverter efficiency (95–97% for modern units), and battery round-trip efficiency (85–95% depending on chemistry). A quote from a certified installer goes through the same math—this just does it in seconds.
| Variable | Definition | Typical Range | Impact on System Size |
|---|---|---|---|
| Daily Energy (kWh) | Total electricity consumption per day | 5–50 kWh residential; 50–200+ kWh commercial | Direct 1:1 relationship — doubling usage doubles array size |
| Peak Sun Hours (PSH) | Equivalent hours of 1,000 W/m² irradiance daily | 3.0–7.0 hours, varies by location & season | Inverse — higher PSH reduces panel count needed |
| System Efficiency (%) | Combined losses: temp, shading, wiring, inverter | 70–80% typical; 85% excellent, 65% poor | Lower efficiency requires proportionally more panels |
| Safety Margin (%) | Oversizing for degradation and cloudy periods | 10–25%; 15–20% recommended | 15% margin = 15% more panels added directly |
| Panel Wattage (W) | Nameplate power rating per solar panel | 400–700W residential; 550W most common | Higher wattage = fewer panels needed (check cost/W) |
Peak load vs. daily energy: not the same thing
Daily energy (kWh) is how much you use over 24 hours. Peak load (kW) is how much you’re drawing at one moment. Run the AC, water heater, and oven simultaneously and you might hit 6 kW—even if your daily total is only 20 kWh.
Surge load is the other number people miss. Motors pull 2–3× their running wattage for a second or two at startup. A 1,500W well pump needs about 4,500W to kick on. Size for running watts only and your inverter trips the first time the pump cycles.
Why peak sun hours are not daylight hours
Peak sun hours (PSH) measure equivalent hours of full 1,000 W/m² irradiance—not how long the sun is up. Miami averages 5.5 PSH. Seattle averages 3.5. Same 10 kW array: 55 kWh/day in Miami, 35 kWh/day in Seattle. That’s a 57% production gap from location alone. Use the Global Solar Atlas to pull the actual figure for your address.
Why Do Solar Panels Never Perform at 100%?
Real-world solar systems deliver 70–80% of their nameplate rating. The losses come from 5 sources: temperature derating (up to 20% in hot climates), shading, soiling, cable resistance, and inverter conversion. Get these wrong in your sizing and a “10 kW system” runs like 7 kW most days.
Solar panels are rated at 25°C (77°F). A summer rooftop in Phoenix or Karachi runs closer to 65°C. That 40°C gap costs roughly 0.4–0.5% efficiency per degree—around 16–20% gone before a cloud appears.
Shading is nastier than most people expect. Cells in a panel wire together in series, so 10% shading on one panel can cut that entire string’s output by 50%. The tree giving you afternoon shade is probably killing 20–30% of daily production. Be honest about this when you enter the shading input.
Soiling varies by climate. Desert installations lose 5–8% annually without regular cleaning. A temperate location with consistent rain? More like 2–3%. Cable resistance adds another 2–5% depending on wire gauge and run length. The calculator applies all of these as separate inputs—so you can see exactly where the losses are coming from.
Run your numbers through the Solar Performance Loss Analyzer before finalizing your design. It shows each derating factor as a percentage of total output—often shading or temperature is the biggest culprit, and fixing it changes your panel count more than anything else.
How Do You Calculate Solar Panel System Size?
Divide your daily kWh by (peak sun hours × system efficiency), then multiply by your safety margin factor. Divide the result by your panel’s wattage for panel count. At 20 kWh/day, 5 PSH, 75% efficiency, 15% margin: you need 6.13 kWp—12 panels at 550W each.
Take a standard home using 20 kWh daily, located in a 5 PSH zone, with system efficiency at 75% and a 15% safety margin built in for degradation over time.
Panel Count = 6.13 kWp ÷ 0.55 kW = 11.1 → round up to 12 panels
Panel configuration matters too. Panels wire in series (raising voltage) or parallel (raising current). Most hybrid inverters accept 500–750V maximum PV input. At roughly 41V per 550W panel, 12 panels in series hits 492V—within limits. The solar sizing calculator handles string optimization automatically based on your inverter specs.
Solar Watt-Hour Calculator Convert appliance wattages into daily kWh to build your accurate load profileHow Many Solar Panels for 1000 kWh per Month? Free Solar Panel Calculator for Home
For 1,000 kWh per month (about 33 kWh daily), you typically need a 10–13 kWp solar array—roughly 18–24 panels rated at 550W each. Exact count depends on your location’s peak sun hours and efficiency losses. In Phoenix (6.5 PSH), 18 panels suffice. In Seattle (3.5 PSH), you’d need closer to 24. Always use your local peak sun hours for accuracy.
Solar Roof Area Estimator Check if your roof can physically fit the panels your system requires before purchasing Solar Power Per Square Meter Calculator Translate available roof space directly into achievable solar capacityHow Do You Size a Solar Battery Bank?
Size batteries using: Battery Capacity (kWh) = (Average Load × Backup Hours) ÷ (DOD × Battery Efficiency). Note “average load,” not peak load—realistic backup usage runs 50–70% of peak. For a 3 kW peak with 6-hour backup, 80% DOD LFP battery: (1.8 kW × 6h) ÷ (0.80 × 0.95) = 14.2 kWh required.
The number on the battery label is total capacity. What you can actually use is different. A 10 kWh LFP battery at 90% depth of discharge gives you 9 kWh. A 10 kWh lead-acid battery at 50% DOD gives you 5 kWh. Same label, very different output. Size based on usable kWh, not nameplate kWh.
LFP vs lead-acid: which battery is right for solar?
LFP (LiFePO4) is the practical choice for daily-cycling solar systems in 2026. It delivers 80–90% usable capacity (vs 50% for lead-acid), lasts 4,000–6,000 cycles (vs 1,000–1,500), and needs essentially zero maintenance. The upfront cost runs 1.5–2× higher, but on a cost-per-kWh-cycled basis over 10 years, LFP wins.
Lead-acid still makes sense for one scenario: a rarely-cycled backup system where upfront cost is the only constraint and space isn’t an issue. Outside that, LFP.
Battery Sizing Calculator Get precise Ah and kWh requirements for your backup duration and chemistry choice Battery Backup Duration Calculator Find out exactly how long your battery bank will last at different load levels| Battery Type | Usable DOD | Efficiency | Cycle Life | Cost/kWh | Best Use Case |
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| Lithium LFP (LiFePO₄) | 80–90% | 95% | 4,000–6,000 | $300–500 | Daily cycling, long-term value, minimal maintenance |
| Lithium NMC | 80–85% | 92% | 3,000–5,000 | $350–550 | Space-constrained, high energy density needs |
| Tubular Lead-Acid | 50–60% | 82% | 1,500–2,000 | $150–250 | Budget builds, infrequent cycling, space available |
| AGM Lead-Acid | 50% | 85% | 500–1,000 | $180–300 | Backup-only systems, sealed enclosure requirements |
| Flooded Lead-Acid | 50% | 80% | 300–700 | $120–200 | Lowest upfront cost where maintenance is acceptable |
💡 Cost Analysis: While LFP costs 2–3× more upfront, it delivers 4–6× more cycles at 80–90% usable capacity vs 50% for lead-acid. Over 10 years, LFP costs less per kWh cycled and requires essentially no maintenance.
What Size Inverter Do You Need for Solar?
Your inverter’s continuous rating must exceed your peak load by 20–30%. A 4 kW peak load needs at least a 5 kW inverter. Also verify the surge rating covers motor startup loads—typically 2–3× the running wattage for a few seconds. For most homes, this means choosing an inverter 1.2–1.5× larger than simple peak load math suggests.
Hybrid vs off-grid vs grid-tie: which inverter type is right?
Hybrid inverters handle solar input, battery charging, and grid connection at the same time. They keep your home running during outages and let you export excess power when rates are good. Most residential installations use hybrid for exactly this reason.
Off-grid inverters make sense only if there’s no utility connection at all. They require larger battery banks to compensate for no grid backup. Grid-tie inverters (no battery port) are the cheapest option but go dark the moment the grid does. If your area has regular outages, this is the wrong choice.
Hybrid costs more upfront. But it lets you add batteries later if budget is tight now, and it handles grid-outage scenarios without a separate system.
Hybrid Inverter Sizing Calculator Determine exact inverter kW rating based on your peak and surge load requirements Hybrid Solar System Planner Plan your complete hybrid system with grid-tie, battery, and solar inputs in one tool PV Array String Configuration Calculator Optimize series/parallel string wiring for your inverter’s MPPT voltage rangeHow Do You Size a Charge Controller for Solar?
Charge controller size (amps) = Total solar array wattage ÷ battery bank voltage × 1.25 safety factor. For a 3,300W array on a 48V system: 3,300 ÷ 48 × 1.25 = 85.9A — round up to a 100A MPPT controller. Always oversize by 25% to handle peak irradiance on cold clear days when panels can briefly exceed nameplate ratings.
The charge controller sits between your solar panels and battery bank. It prevents overcharging, manages the charging profile, and — in the case of MPPT controllers — converts excess PV voltage into additional charging current. Most people undersize this component because they calculate at standard irradiance. On a cold, bright day, panels can produce 10–25% above their rated wattage.
MPPT vs PWM: which charge controller is right?
MPPT (Maximum Power Point Tracking) controllers are the right choice for systems over 200W. They track the panel’s optimal operating voltage and convert any excess voltage into current — delivering 15–30% more energy than PWM from the same panels. A 48V system with panels wired at 150V input uses all that voltage productively.
PWM (Pulse Width Modulation) controllers waste any panel voltage above the battery voltage. A 36V panel on a 24V PWM system throws away roughly 33% of available power. PWM only makes sense for tiny systems under 200W where cost is the only consideration.
| Feature | MPPT Controller | PWM Controller |
|---|---|---|
| Efficiency | 93–98% | 70–80% |
| Best for | 200W+ systems, high-voltage strings | Small systems under 200W |
| PV input voltage | Up to 150V or 250V depending on model | Must match battery voltage closely |
| Cold weather | Captures excess voltage as extra current | Wastes voltage above battery level |
| Cost | $80–$400 for quality units | $15–$80 |
| Brands | Victron SmartSolar, Epever Tracer, Renogy Rover | Renogy Wanderer, generic units |
Victron SmartSolar MPPT controllers include Bluetooth monitoring — you can watch every amp in real time from your phone. For off-grid installs where you can’t easily check the controller, remote monitoring is worth the price difference over generic brands.
How Do You Size Wires for a Solar System?
Wire sizing depends on current flow and cable distance. PV string wiring (high voltage, low current) typically uses 4–6 mm² (10–12 AWG). Battery-to-inverter wiring (low voltage, very high current) demands 25–35 mm² (4–2 AWG) minimum—even for short runs under 0.5 meters. Never apply PV wire sizing to DC battery cables; the difference can cause fires.
A 5 kW inverter on a 48V system pulls 104A continuously (5,000W ÷ 48V). This demands 25–35 mm² cable for the battery connection—despite very short runs. Meanwhile, panels wired in series at 12 × 41V = 492V carry only 13–14A, allowing much smaller wire over long roof runs. According to the National Electrical Code Article 690, voltage drop on solar circuits should stay under 3%.
| Application | Wire Size (mm²) | Wire Size (AWG) | Max Current | Notes |
|---|---|---|---|---|
| PV String (per string) | 4–6 mm² | 12–10 AWG | 13–18A | UV-rated PV cable, MC4 connectors, separate run per string |
| Battery → Inverter (48V) | 25–35 mm² | 4–2 AWG | 70–130A | Keep under 0.5m length; use lugs; never skimp here |
| Battery → Inverter (24V) | 35–50 mm² | 2–1 AWG | 130–200A | Double current vs 48V; very short runs essential |
| Inverter AC Output (Small) | 2.5–4 mm² | 14–12 AWG | 10–20A | Standard electrical wire; match breaker sizing |
| Inverter AC Output (Large) | 6–16 mm² | 10–6 AWG | 25–60A | Heavier gauge for high-power inverters over 5 kW |
| Grounding/Earth Wire | 6 mm² | 10 AWG | N/A (safety) | Bare copper; bond all equipment; earth rod <5Ω |
How Does Location Affect Solar System Size?
Location shapes your solar system size through 3 inputs: peak sun hours (3–7 hours depending on latitude and season), ambient temperature (hot climates add 15–20% efficiency losses), and seasonal variation (temperate zones see 2–3× production swings between summer and winter). Get your location parameters right and the rest of the calculation follows accurately.
Tropical regions run at 5–6 PSH year-round—design for the annual average with a 10–15% margin and you’re done. Temperate zones are trickier. Summer peaks at 6–7 hours drop to 3–4 in winter. A system sized for summer in Seattle or the UK will run short from November through February. Size for winter if year-round independence is the goal.
PV Panel Tilt & Orientation Optimizer Find the ideal tilt angle and azimuth for maximum annual yield at your latitude| Region | Annual Avg | Summer Peak | Winter Low | Design Tip |
|---|---|---|---|---|
| Tropical | 5.5 hrs | 5.8–6.2 hrs | 5.0–5.5 hrs | Design for annual average — minimal seasonal variation |
| Subtropical | 5.0 hrs | 5.8–6.5 hrs | 4.0–4.5 hrs | Add 15% margin or accept seasonal grid use in winter |
| Temperate | 4.2 hrs | 6.0–7.0 hrs | 2.5–3.5 hrs | Design for winter (+30%) or use grid-tied net metering |
| Arid/Desert | 6.5 hrs | 7.5–8.5 hrs | 5.0–6.0 hrs | Excellent resource — increase temperature derating by 20% |
| South Asia / Pakistan / India | 5.5–5.8 hrs | 6.5–7.2 hrs | 4.5–5.0 hrs | Excellent solar resource; add 18–22% temp derating for summer rooftop heat |
| Middle East / UAE / Saudi | 6.0–6.5 hrs | 7.0–8.0 hrs | 5.0–5.8 hrs | Among the world’s best solar resource; dust/sand soiling up to 8% — clean monthly |
| Polar/Nordic | 3.0 hrs | 8.0–10.0 hrs | 0.5–2.0 hrs | Extreme seasonal variation — hybrid systems essential |
💡 Micro-climate note: Coastal fog, mountain shading, and urban pollution can reduce these values 10–25%. Always verify at your specific address using Global Solar Atlas.
Solar vs Grid Cost Comparison See how your local electricity rate and sun hours affect solar payback in your region Solar Net Metering Financial Calculator Calculate exactly what grid exports earn you under your utility’s net metering programHow to Use the Solar Sizing Calculator: Step-by-Step
Use the calculator in five steps: analyze your load profile (daily kWh, peak load, surge load), set location parameters (climate, sun hours, temperature, shading), choose equipment specs (panel wattage, battery chemistry, inverter type), fine-tune advanced settings, then click Calculate to receive your full panel count, battery size, inverter rating, and wiring specifications.
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Analyze your load profile
Pull 3 months of electricity bills and divide total kWh by 90. That’s your daily average. For peak load, add up every appliance you might run simultaneously during your heaviest-use moment—kitchen at dinner, AC running, water heater recovering. For surge load, take your biggest motor (well pump, AC compressor) and multiply its running wattage by 3. Set backup duration based on how long your area’s outages typically last. Four hours covers most places; 8–12 hours if you’re somewhere with unreliable grid or medical equipment that can’t go dark.
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Set location parameters
Pick your regional climate or enter your peak sun hours directly from NREL PVWatts. Set ambient temperature for the season when you consume the most. Be honest about shading—run a solar pathfinder app if you’re not sure. Set soiling factor based on local rainfall and how often you’ll actually clean the panels (be realistic, not optimistic).
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Choose equipment specs
550W panels are the practical residential choice right now—wide availability, solid warranty coverage, reasonable cost per watt. For battery chemistry, LFP handles daily cycling well; lead-acid only makes sense for rarely-used backup on a tight budget. System voltage: 48V for most homes, 110V+ for commercial. Inverter type: hybrid if you have grid access, off-grid only if you don’t.
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Fine-tune advanced settings
Most users can skip this tab on a first pass. When you’re ready: set battery efficiency (95% for LFP, 80–85% for lead-acid), cable loss (under 2% for quality installs, up to 5% for long runs), mismatch loss (2% standard, 3–4% if mixing panel ages or brands), and safety margin (15% standard, 20–25% for conservative designs that need to hold up over 20+ years). These adjustments move the final number by 5–10%.
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Calculate and read the results
Click Calculate to see solar array size (kWp and panel count), battery capacity (kWh and Ah at system voltage), inverter rating (kW continuous), and daily generation estimate. Cross-check panel count against available roof space—550W panels average 2.3 m² each. If daily generation matches or exceeds consumption, the system covers your load. At 70–80% coverage, you’ll still pull from the grid on cloudy days and in winter.
Watch: Solar Sizing Calculator — Full Walkthrough (5 min)
See exactly how to enter your load profile, location, and equipment specs to get your system design in minutes.
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Real-World Solar System Size Examples
25 kWh/day | 5 kW Peak | 8-Hour Backup
First-year performance: 11,800 kWh generated, 9,125 kWh consumed, 2,675 kWh exported. Backup activated 3 times during storms, providing 7–8 hours each time. System achieved 95% summer and 75% winter energy independence.
8 kWh/day | 2 kW Peak | 48-Hour Backup
Ground-mounted at 55° tilt for winter optimization and snow shedding. Array oversized 40% for winter. Winter provides 85% of energy needs; propane supplements heating during worst weeks. Battery cycles 200–250 times annually—well within 6,000-cycle LFP rating.
Free Solar Sizing Calculator for RV and Off-Grid Systems
RV solar systems typically run 400–1,200W of panels, 100–300Ah of LFP battery (12V or 24V), and a 2,000–3,000W inverter-charger. Off-grid cabins need 3–8× more capacity with 48–72 hours of battery backup. Both use the same sizing formula — but RV systems are constrained by roof space, weight, and 12/24V wiring rather than energy need alone.
Solar sizing calculator for RV
RV solar design has 3 constraints that a home system doesn’t: roof space (typically 6–12 m² usable), weight limits (most RV roofs handle 15–25 kg of panels), and 12V or 24V wiring throughout the vehicle. A typical Class A motorhome running fridge, lights, fans, and phone charging uses 3–6 kWh daily. That needs 400–800W of panels at 5 PSH to stay balanced.
Use 200W panels for RVs — they’re physically smaller (about 1.1 m² each), lighter, and fit the curved or obstructed roof areas that 550W residential panels can’t. Wire at 24V if possible; it halves your current versus 12V and allows thinner cables throughout.
4 kWh/day | 1.5 kW Peak | 2-Day Backup
Full-time use across the US Southwest. System covers 95% of energy needs April–October with no shore power. 2 days of autonomy before needing hookup or generator. Total system weight: 68 kg including batteries.
Off-grid solar sizing calculator
Off-grid sizing is more demanding than grid-tied because there’s no utility backup. Your battery bank has to carry you through 2–5 consecutive cloudy days depending on your climate. In Pakistan or UAE that means 1–2 days is enough. In a Nordic cabin, design for 5 days minimum.
The formula is the same as a grid-tied system — but the safety margin grows to 20–30%, battery backup extends to 48–96 hours, and your panel array oversizes by 30–40% for winter production. Off-grid isn’t harder to calculate, just less forgiving when the math is wrong.
Battery Backup Duration Calculator Calculate exactly how many days your battery bank lasts at your actual load levelWhat Are the Biggest Solar Sizing Mistakes to Avoid?
The 7 most costly solar sizing mistakes: confusing kW with kWh, ignoring motor surge loads, underestimating shading, sizing for summer in a temperate climate, overlooking battery discharge limits, applying 12V wire math to 48V systems, and skipping temperature derating. Any one of these can make a correctly-sized system on paper fail in practice.
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Confusing kW with kWh — Daily energy is total consumption (15 kWh). Peak load is maximum simultaneous demand (4 kW). These measure different things. Using kW where kWh belongs multiplies sizing errors by 10–20×.
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Ignoring surge loads — Motors pull 2–3× their running wattage for 1–2 seconds at startup. A 1,500W pump needs 4,500W to kick on. Size only for running watts and your inverter trips every time the pump cycles.
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Underestimating shading — That tree casting afternoon shadows is probably costing 20–30% of daily production. Use a solar pathfinder app for an honest measurement. People consistently guess 5% and lose 25%.
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Sizing for summer in a temperate climate — Winter sun hours in Seattle, the UK, or Central Europe drop 40–60% from summer peaks. A system that covers your load in July will run short from November through February. Size for winter if you want year-round coverage.
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Ignoring battery discharge limits — A 10 kWh battery at 50% DOD delivers 5 kWh usable. Label says 10 kWh; your backup runs out in half the time you planned. The calculator applies DOD automatically—a manual spreadsheet often doesn’t.
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Applying 12V wire math to 48V systems — Current scales inversely with voltage. A 5 kW load draws 416A at 12V but only 104A at 48V. Wire sized for 12V on a 48V system overheats. Always calculate at your actual system voltage.
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Skipping temperature derating — Panels are rated at 25°C. A summer rooftop runs at 60–65°C. That 40°C gap costs 16–20% of rated output. Ignore it and your “correctly sized” array runs consistently short on hot days—which is exactly when you need it most.
Frequently Asked Questions About Solar Sizing
What is a solar sizing calculator?
A solar sizing calculator determines how many solar panels, how much battery storage, and what inverter size you need based on your daily energy use, location, backup needs, and equipment choices. It applies real efficiency losses—temperature, shading, cable resistance, inverter conversion—so the output reflects what your system will actually produce.
How do I calculate what size solar system I need?
Divide your daily energy use (kWh) by your location’s peak sun hours, then divide again by system efficiency (typically 0.75). Multiply by a 1.15–1.20 safety margin for panel degradation over time. At 20 kWh/day, 5 PSH, 75% efficiency: 20 ÷ (5 × 0.75) × 1.15 = 6.13 kWp.
How many solar panels do I need for 1000 kWh per month?
For 1,000 kWh per month (about 33 kWh daily), you need roughly 10–13 kWp—18–24 panels at 550W each. In Phoenix at 6.5 PSH, 18 panels get you there. In Seattle at 3.5 PSH, you need closer to 24. Location drives the difference more than anything else.
What is the best battery for an off-grid solar system?
Lithium LFP (LiFePO4) is the right choice for most off-grid solar systems. It delivers 80–90% usable depth of discharge, 95% round-trip efficiency, and 4,000–6,000 cycle lifespans. That’s 3–4× longer than lead-acid at roughly the same 10-year cost when you factor in replacement cycles.
What size inverter do I need for my solar system?
Your inverter’s continuous rating should exceed your peak load by 20–30%. A 4 kW peak load needs at least a 5 kW inverter. Also check the surge rating—motor startup currents hit 2–3× running wattage for a second or two. Size the inverter for surge, not just steady-state operation.
How much does a home solar system cost in 2026?
A 6–8 kW solar array with 12–15 kWh LFP batteries and a hybrid inverter runs $12,000–$22,000 installed before incentives in 2026. Federal tax credits and state rebates typically cut 30–40% off that. Commercial systems cost more but often pay back faster because commercial electricity rates are higher.
Can I use this solar sizing calculator for an RV or off-grid cabin?
Yes. The calculator has presets for RVs, cabins, and farms. Select the Off-Grid inverter type and set backup duration to 48–72 hours for a remote cabin. For RV roofs, drop panel wattage to 200–350W—smaller panels fit tighter spaces and still work fine at lower voltages.
What is the biggest mistake people make when sizing a solar system?
Sizing for summer in a temperate climate. Winter sun hours drop 40–60% from summer peaks in places like the UK, northern US, or Central Europe. A system that covers 100% of your load in July might cover 40% in January. Run the calculation using your winter PSH if year-round coverage matters.
Run the numbers before you buy anything
You’ve got the full picture now: the sizing formula, where the losses actually come from, how battery chemistry changes your usable capacity, and why your location’s winter PSH matters more than summer’s.
Start with 3 months of electricity bills. Find your average daily kWh. Then use the solar sizing calculator at the top of this page—it takes under 5 minutes and gives you a complete component list, not just a panel count.
Try the Free Solar Sizing Calculator →Sources & Further Reading
Last Updated: | Next Review:
- World Bank / Solargis. “Global Solar Atlas 2.0 — Solar Resource & PV Power Potential.” 2025.
- National Fire Protection Association. “NEC Article 690 — Solar Photovoltaic Systems.” 2023 Edition.
- ENERGY STAR (U.S. EPA). “Solar Energy Systems Tax Credit.” 2026.
- International Renewable Energy Agency (IRENA). “Renewable Power Generation Costs 2024.” 2025.
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