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Solar PV & Battery Sizing Engine
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Solar Panel, Battery & Payback Calculator

Enter your monthly kWh usage or electricity bill to size your rooftop solar PV system: number of panels, inverter, LiFePO4 battery bank, breakers and wire sizes, plus your 25-year financial savings. Have questions while sizing? Click the AI Advisor button in the bottom-right corner for real-time engineering recommendations tailored to your live energy numbers.

Quick Presets:

1. Electricity Consumption

Demand
Monthly Energy Usage From your monthly electric bill
kWh
Or Average Monthly Bill Auto-syncs with kWh
$

2. Location & Sunlight

Sun Hours
Peak Sun Hours (PSH) Daily average solar irradiance
hrs

3. System Type & Goal

Topology
Target Solar Offset % of consumption to cover
%

4. Battery Storage Sizing

Backup
Backup Duration / Autonomy Days of continuous backup
days
Essential Backup Load % of daily consumption powered by battery
%
Blackout Backup Run-Time BMS Safe
Continuous Appliance Power Enter your specific load
Watts
Will run for: -- hrs
Design Safety Factor 1.30× Engineering design buffer (temperature, wiring & dust derate)
×
DC Cable Run Distance (One-Way) Used for Voltage Drop Index (VDI) wire gauge sizing
ft
Pricing & Tariff Parameters
$
$
$
%
Solar PV & Energy Storage Feasibility Proposal

Generated on | Recommended System:

Recommended Solar PV ☀️
-- kWp
--
Roof Space Needed 📐
--
Clear unshaded roof area
Battery Storage 🔋
--
--
Est. Year 1 Savings 💵
--
Clean electricity bill reduction
Payback Period ⏱️
--
Breakeven horizon
25-Year Net Profit 📈
--
--

Performance & Financial Charts

ERA5 Satellite Mode

Technical Sizing Specifications

System Specs
Daily Average Consumption --
Annual Energy Demand --
Installed DC Solar Capacity --
Recommended Inverter Capacity (AC) --
Solar Modules Required --
PV Stringing & MPPT Layout --
DC PV Solar Cabling & Fuses --
AC Main Grid Circuit Breaker --
Charge Controller / MPPT Current --
Voltage Drop Index (VDI) --
Estimated Roof Surface Area --
Estimated Daily Solar Generation --
Estimated Annual Solar Generation --
Solar Energy Coverage Ratio --
Battery Storage Capacity --
Battery Bank Configuration --
Battery DC Cable & Breaker --
Battery Technology / Chemistry --

Financial Investment & Return Analysis

Economics
Solar Panels & Racking Hardware --
Inverter & Power Electronics --
Battery Storage Bank --
Balance of System & Installation Labor --
Gross Estimated System Cost --
Government Tax Credit / Subsidy --
Net Total Out-of-Pocket Investment --
Estimated Year 1 Utility Bill Savings --
Simple Payback Period --
Cumulative Lifetime Net Profit --
Lifetime Return on Investment (ROI) --
Annual CO₂ Avoided
--
25-Yr Lifetime CO₂
--
Trees Equivalent
--
Car Travel Offset
--

How to Use This Solar Calculator

  1. Enter your energy use. Type your average monthly consumption in kWh (shown on your electric bill), or enter your monthly bill amount and we'll estimate the kWh from your local tariff.
  2. Set your location's Peak Sun Hours (PSH). Most of the Philippines, India, Australia and the southern USA get 4.0 to 5.5 PSH. Northern Europe gets 2.5 to 3.5.
  3. Choose a system type. Grid-Tied has the fastest payback. Hybrid adds battery backup for brownouts. Off-Grid runs completely without the utility.
  4. Review the results. You'll see recommended kWp, panel count, inverter size, battery capacity (kWh and Ah), breaker and wire sizes, and a 25-year cash-flow chart. Then export a PDF proposal.

How many solar panels do I need?

Divide your daily energy use by your Peak Sun Hours and a system efficiency of about 80%: kWp = (monthly kWh ÷ 30) ÷ PSH ÷ 0.80. For example, a home using 450 kWh/month with 4.5 PSH needs about 4.2 kWp, which is 8 panels of 550 W and roughly 20 m² of unshaded roof.

What battery size do I need for solar?

Multiply the energy you want to cover at night or during brownouts by your backup days, then divide by the battery's usable depth of discharge. LiFePO4 batteries allow about 90% DoD and 6,000+ cycles, so a 10 kWh nightly load needs about an 11–12 kWh LiFePO4 bank (around 230 Ah at 48 V).

How long is the solar payback period?

Grid-tied systems usually pay for themselves in 3 to 6 years where electricity costs are high (such as the Philippines, Australia and Europe). Hybrid systems with batteries usually take 6 to 9 years. The calculator includes 0.5%/year panel degradation, 3.5%/year tariff increases, maintenance, and an inverter replacement around year 12.

Have questions? Ask our built-in AI Solar Engineering Advisor

Need guidance choosing between microinverters and hybrid string inverters, or sizing backup autonomy for inverter air conditioners? Click the AI Advisor button in the bottom-right corner. Our intelligent solar assistant analyzes your active calculation inputs in real time, explaining technical formulas, battery autonomy hours, and PEC & NEC wiring standards in clear, actionable detail.

New to solar? Compare standard solar system sizes, learn about system architectures, or read our solar sizing FAQ.