energy calculator
Estimate system size and cost from monthly kWh usage, sun hours, cost per watt, and tax credit.
Going solar can dramatically cut your electric bill, but it’s hard to know what size system you need and what it might cost before you start collecting quotes. Installed prices are usually quoted in dollars per watt, and incentives like the federal tax credit reduce the net cost, but tying those pieces together from a monthly bill can be confusing.
This solar panel cost calculator gives you a quick, ballpark estimate of system size and cost based on your monthly kWh usage, local sun hours, assumed system efficiency, installed cost per watt, and tax credit rate. It converts your monthly energy usage into an estimated system size in kilowatts (kW) and watts (W), then multiplies by your cost‑per‑watt assumption to get an estimated gross cost. Finally, it applies a user‑entered tax credit percentage (like the 30% federal credit in the U.S.) to show estimated tax credit dollars and a net cost after that credit.
Use it to frame your expectations before talking with installers, sanity‑check quotes, and see how changing assumptions like sun hours or cost per watt affect your budget. It’s not a design or production simulator—just a transparent way to turn your power bill into rough system sizing and cost numbers.
The calculator starts with your Monthly electricity use (kWh) from your utility bill and converts it into an average Daily kWh by dividing by 30. This provides a rough estimate of how much energy your solar array would need to produce per day on average to offset that usage.
You provide Average sun hours per day for your location. “Sun hours” here means peak‑sun‑equivalent hours, not just daylight. For example, many U.S. locations fall somewhere between 4 and 6 peak‑sun hours per day, depending on latitude, climate, and shading.
You also enter a System efficiency percentage, which accounts for inverter losses, wiring losses, soiling, and other real‑world factors. The calculator converts this to a decimal efficiency factor (for example, 90% → 0.90) when sizing the array.
To estimate the required system size in kilowatts, the calculator uses a simplified relationship: Required kW ≈ Daily kWh ÷ (Sun hours × Efficiency factor). This says that the array’s nameplate power, multiplied by daily sun hours and adjusted for efficiency, should roughly match your daily energy usage.
Once the required system size in kW is calculated, the tool multiplies by 1,000 to compute the System size (W). This wattage is what installers typically quote when they talk about a “7.2 kW” or “10 kW” system.
You then specify an installed Cost per watt ($/W). The calculator multiplies system watts by this number to estimate the Gross cost of the system before incentives. This cost should include equipment, labor, permitting, and typical soft costs if you’re modeling a turnkey quote.
Finally, the calculator applies your Tax credit rate (%) to the gross cost to estimate a single Tax credit amount and subtracts that from the gross cost to produce an Estimated net cost. This assumes the credit is a simple percentage of system cost and that you have enough tax liability to use it.
The outputs are meant as directional guidance: they give you an order‑of‑magnitude view of system size and price, not exact design or quote numbers.
Daily kWh = Monthly kWh ÷ 30 Efficiency factor = System efficiency (%) ÷ 100 Required kW ≈ Daily kWh ÷ (Sun hours × Efficiency factor) System watts = Required kW × 1,000 Gross cost ≈ System watts × Cost per watt ($/W) Tax credit ≈ Gross cost × (Tax credit rate ÷ 100) Net cost ≈ Gross cost − Tax credit
Use this solar panel cost calculator to turn your monthly electric bill into an estimated system size and cost. Enter your monthly kWh, local sun hours, system efficiency, cost per watt, and tax credit rate to see approximate system size in kW and watts plus gross and net cost.
The tool is ideal for homeowners who want a transparent, back‑of‑the‑envelope view of solar economics before collecting bids. By breaking the math into clear steps—sizing from kWh, multiplying by cost per watt, and applying a tax credit—it helps you quickly compare different scenarios and installer quotes.
Because the model is intentionally simple, you can easily pair its outputs with more detailed production estimates from installers, utility incentive calculators, and financing projections to build a complete view of your solar investment.
This solar panel cost calculator provides simplified estimates of system size, gross cost, tax credit, and net cost based on user‑entered assumptions. It does not simulate detailed energy production, account for all site‑specific factors, or guarantee eligibility for incentives. Treat the outputs as ballpark planning numbers only and confirm actual sizing, pricing, and incentive details with qualified solar installers and tax professionals before making purchase or financing decisions.
