Solar System Size Calculator
Estimate the solar system size, panel count, and battery capacity needed for your electricity usage.
Homeowner planning tool
Solar System Size Calculator
Calculate the solar system you need from your electricity usage, or enter a system size you already have in mind.
Choose Calculation Method
Choose whether you want to calculate the required system size or see what a specific system can provide.
Result Summary
Your Solar Power Requirement
Enter your information and calculate your solar requirements.
Solar System Size
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Solar Panels Required
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Daily Electricity Generation
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Monthly Electricity Generation
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Annual Electricity Generation
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Battery Storage Required
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Battery Capacity
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Results are estimates based on the values entered. Actual solar production varies with weather, shading, roof orientation, equipment, temperature, seasonal sunlight, and other site conditions.
Sizing follows usage, not roof area. This calculator converts your bill into annual kWh and then into the kilowatts required to cover the share of usage you choose.
What the model assumes
Every estimate rests on assumptions, and hiding them is how bad solar math spreads. Here is exactly what this tool uses.
- City-average residential retail rate in cents per kWh
- City-average daily peak sun hours from long-run irradiance data
- 14% combined system losses for inverter, wiring, soiling, and heat
- 410-watt modules and installed cost per watt from current Texas market pricing
- 0.5% annual panel degradation across a 25-year model
- 3.1% annual utility rate escalation, close to the long-run Texas average
- 30% federal residential clean energy credit on the full installed cost
What it does not know about your home
A calculator cannot see your roof. It does not know your roof dimensions, available roof area, roof sections, shading, or obstructions such as vents and skylights. To estimate how many solar panels could physically fit on your roof, use our Solar Roof Panel Calculator. It can help you compare your available roof area with panel dimensions and estimate the number of panels that may fit. A roof-layout estimate is still different from a professional site assessment, which can account for roof structure, setbacks, shading, and electrical requirements.
It also cannot know your retail electric provider's solar buyback rate, which in Texas is the single largest swing factor in real-world savings. Read how Texas buyback works before you finalize a system size.
How to use the result
Take the system size and net cost into your first installer conversation. If a proposal comes back 40% above this estimate for the same kilowatts, ask what is different: a panel upgrade, a service panel replacement, or a financing dealer fee. All three are legitimate reasons for a higher price, and all three should be itemized.
Then check your city page for local rate and utility detail, and confirm which Texas incentives you qualify for.