5 Solar Calculators · Free · Offline

Solar Calculations,
Finally Simple

Figure out how much power your panels will produce, how to wire them together, how long your batteries will last, and when a solar setup pays for itself — all without an internet connection.

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PV Toolbox
Solar Calculators
● 5 Tools
⊘ Offline
⚡
kWh
Solar Output
Daily & annual production
〰️
V
String Sizer
Temp-derated string sizing
🔋
Ah
Battery Storage
Autonomy bank sizing
⎇
cfg
Array Optimizer
Mixed wiring configs
📈
yrs
Payback Period
ROI & break-even analysis
Array Optimizer
Combined Array
8
Panels
857 W
Rated
35.7 V
Eff. Vmp
3.4 A
Eff. Imp
Wiring Options
4S × 2P Compatible
142.8 V
Vmp
6.8 A
Imp
857 W
Power
Harvest Rate97.4%
Array wire: 10 AWG
8S × 1P Compatible
285.6 V
Vmp
3.4 A
Imp
971 W
Power
Harvest Rate89.1%
Array wire: 14 AWG
5
Solar Calculators
100%
Offline — No Internet Required
NEC
690.8 Wire Sizing Guidance
Free
No Subscription, No Ads
Calculators

Five Tools That Answer
the Real Questions

How much energy will my panels produce? How big a battery do I need? Which wiring makes the most sense? PV Toolbox puts the math right in front of you.

kWh
Solar Output
Estimate daily and annual energy production from any PV array. Factor in panel wattage, peak sun hours, and system efficiency to get real-world kWh numbers fast.
Daily kWh Annual kWh System Efficiency Peak Sun Hours
V
String Sizer
Calculate safe series string lengths with full temperature derating. Ensures Voc stays within inverter limits across all operating temperatures — cold morning starts and peak summer heat.
Voc Max / Vmp Range Temp Derating Min/Max Strings Inverter Compatibility
Ah
Battery Storage
Size your battery bank for days of autonomy. Input your daily load, desired backup days, depth of discharge, and battery chemistry to get the exact amp-hour capacity you need.
Days of Autonomy Depth of Discharge Lead-Acid / Lithium Bank Sizing
yrs
Payback Period
Calculate return on investment and break-even timeline. Factor in system cost, incentives, utility rates, and rate escalation to see exactly when your solar setup starts paying for itself.
ROI Analysis Break-Even Year Incentives / Rebates Rate Escalation
cfg
Array Optimizer
The most powerful tool in the kit. Mix multiple panel types, compare every series/parallel wiring configuration, and see exactly how mismatch losses and MPPT compatibility affect real harvest rate. Includes wiring diagrams and NEC 690.8 wire sizing.
Mixed Panel Types Mismatch Loss MPPT Compatibility Wiring Diagrams Harvest Rate NEC Wire Sizing
Why PV Toolbox

Answers You Can
Actually Trust

Most solar calculators are buried in desktop software or require an internet connection. PV Toolbox gives you the same math on your phone, whenever you need it.

Fully Offline
No internet required — ever. Every calculation runs entirely on-device. Whether you're in a field, a garage, or somewhere with no signal, it works exactly the same.
NEC Referenced
Wire sizing guidance follows NEC 690.8 (156% design current factor). Conductor recommendations reference 90°C copper at 40°C ambient — so the numbers you get are grounded in a real standard, not guesswork.
Transparent Calculations
Every number is shown with its formula and assumptions. No black boxes. The disclaimer is up front — these are engineering estimates, and PV Toolbox treats you as someone smart enough to know the difference.
Visual & Intuitive
Results aren't just numbers — the Array Optimizer generates wiring diagrams you can understand at a glance, with color-coded bus bars, panel layouts, and harvest rate progress bars.
Free, No Nonsense
No accounts to create, no subscription tiers, no ads between calculations. Download it, open it, calculate. That's it.
Mix-and-Match Panels
The Array Optimizer handles setups with different panel models in the same array. It quantifies the mismatch penalty so you can make an informed decision rather than guessing.
Array Optimizer

Wiring Decisions,
Made Simple

Every series/parallel combination of your panels, ranked by real harvest rate. See exactly what you gain or lose before you run a single wire.

Every Configuration, Ranked
All valid series × parallel combinations of your array are automatically enumerated and sorted by harvest rate — highest first.
Mismatch Loss Quantified
When mixing panel types, mismatch loss is calculated from weighted Vmp/Imp averages and shown as a percentage against rated power — so you know the real cost of reusing old panels.
Harvest Rate Breakdown
Rated power → mismatch loss → MPPT loss → final harvest rate. Each step shown separately so you know exactly where energy is being lost.
Wiring Diagrams Included
Tap any result card to see a custom wiring diagram — panel grid, series connections, bus bars, voltage and current labels — generated on the fly for that exact configuration.
Array Optimizer — Results
8
Total Panels
971 W
Rated Power
35.7 V
Eff. Vmp
3.4 A
Eff. Imp
4S × 2P Compatible
142.8 V
Vmp
6.8 A
Imp
971 W
Power
Harvest Rate97.4%
⎍ Array wire: 10 AWG
2S × 4P Compatible
71.4 V
Vmp
13.6 A
Imp
971 W
Power
Harvest Rate91.2%
⎍ Array wire: 8 AWG
All Parallel MPPT Miss
35.7 V
Vmp
27.2 A
Imp
971 W
Power
Harvest Rate21.8%
⎍ Array wire: 6 AWG
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