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Solar Utility Bill Audit Calculator

Enter 12 months of electricity bills — get your annual total, peak season analysis, seasonal variation, TOU exposure, hidden fees, and optimal solar system size recommendation.

Household & utility info
Monthly bills (12 months)
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Utility Bill Audit Results
$3,135/year — $261/month average
Annual total
$3,135
Monthly average
$261
Peak season avg (Jun-Sep)
$373/mo
Off-peak avg
$206/mo
Seasonal variation
81% — great for solar!
Highest bill month
Jul ($420)
Estimated annual kWh
26,125 kWh
Avg rate used
$0.12/kWh
TOU RATE EXPOSURE
You likely pay TOU peak rates. Solar production peaks at midday — shifting EV charging and appliance use to solar hours can significantly reduce your bill even before net metering credits.
HIDDEN FEES IDENTIFIED
Distribution charge ($15–35/mo)
Customer/service charge ($10–20/mo)
Fuel adjustment charge (variable)
SOLAR SYSTEM RECOMMENDATION
Based on your 26,125 kWh annual consumption, a 8–12 kW system (sized for typical family consumption) is recommended. This could offset $1,542–$2,313/year in electricity costs.
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How to Use This Calculator

Enter your 12 monthly bills

Pull 12 months of electricity bills — your utility's online portal makes this easy. Enter each month's total bill amount including all fees and charges. If a month is estimated, use the closest available figure. The calculator analyzes your full annual pattern, not just averages, to identify when your usage peaks and how much seasonal variation you have.

Select your household type and seasonal pattern

Household type determines which hidden fees to flag and what system size range to recommend. A family with EV charging has very different solar needs than an empty-nester. The seasonal pattern dropdown identifies whether you're a strong solar candidate — summer-peak households (AC-heavy, warm climates) get the most value from solar because production peaks coincide with your highest bills.

Read the bill analysis and solar recommendation

The results show your peak season vs. off-peak breakdown, seasonal variation percentage (greater than 40% is excellent for solar), TOU rate exposure, hidden fixed charges you can't eliminate with solar, and a recommended system size range. Monthly savings projections show how different system sizes would affect your annual spend.

The Formula

Annual Total = Sum of 12 monthly bills Monthly Average = Annual Total ÷ 12 Peak Season Average = Sum(Jun+Jul+Aug+Sep) ÷ 4 Seasonal Variation % = (Peak Avg - Off-Peak Avg) ÷ Off-Peak Avg × 100 Estimated kWh = Annual Total ÷ Average Rate ($/kWh) Recommended kW = Annual kWh ÷ (365 days × Peak Sun Hours × 0.80 efficiency)

Seasonal variation above 40% indicates your usage pattern is well-aligned with solar production peaks. Solar panels generate the most electricity in summer months — exactly when summer-peak households spend the most on electricity. This alignment maximizes net metering value and bill offset. Hidden fixed charges (customer charge, distribution fee) remain on your bill even at 100% solar offset — these costs are unavoidable regardless of system size.

Example

Texas family with EV — optimal solar candidate

The Martinez family in Texas runs two EVs, central AC, and a pool pump. Their summer bills spike to $420-450 while winter months average $240. They're charged distribution and customer fees every month regardless of usage.

Annual electricity spend$3,840
Peak season avg (Jun-Sep)$432/month
Off-peak avg (Oct-May)$255/month
Seasonal variation69% — excellent for solar
Estimated annual kWh32,000 kWh
Recommended system10–16 kW

With a 14 kW system in Texas (5.5 peak sun hours), the Martinez family could generate ~22,000 kWh/year — offsetting roughly 69% of their annual electricity cost. The fixed distribution and customer charges (~$600/year) remain regardless of solar production, giving a realistic annual savings of ~$2,300 after accounting for unavoidable fixed fees.

FAQ

Every utility charges fixed fees that apply to all connected customers regardless of how much or how little electricity they consume. These typically include a customer charge ($10-20/month), distribution charge ($15-35/month), and various local fees. Even a homeowner generating 100% of their electricity with solar will still receive a monthly bill with these fixed costs — typically $15-40/month minimum. Only off-grid homes with battery storage and no utility connection avoid all fees.
Time-of-use (TOU) pricing means your utility charges different rates depending on when you use electricity — peak hours (typically 4-9pm) cost significantly more than off-peak hours. Solar is most valuable when it generates power during expensive peak hours or when it enables you to export excess energy back to the grid at peak rates. Pairing solar with a battery lets you charge from solar midday and discharge during expensive evening peak hours, maximizing savings on TOU plans. EV owners benefit especially from shifting charging to solar midday hours.
Yes — and here is why. Solar panels produce the most electricity in summer months when the sun is highest and days are longest. If your electricity bill is also highest in summer (due to air conditioning), the production peaks align with your demand peaks. Every kWh your solar system produces in June, July, August, and September offsets your most expensive electricity. High seasonal variation means solar is working hardest exactly when you need it most. By contrast, a home with electric resistance heat that peaks in January will see solar production offset relatively cheaper winter electricity while generating a surplus in summer that may not be fully utilized.
Beyond the energy charge (cents/kWh), electricity bills typically include: Customer charge — a fixed monthly fee just for being connected, typically $10-20. Distribution charge — pays for power line maintenance, $15-35/month. Fuel adjustment charge — passes through fuel cost changes to customers, variable. Capacity charge — in some areas charges for your peak demand during a billing period. Franchise fee — a local government fee utilities pass through. Renewable portfolio standard charges — funds state-mandated clean energy programs. Demand charges — more common for commercial accounts but occasionally applied to large residential users. Solar systems reduce your energy charge but cannot eliminate most fixed charges.
You need all 12 months to get an accurate picture. Seasonal variation is the most important factor in solar ROI analysis — if you only have 3-6 months, you may be missing the highest or lowest bills that define your peak-to-valley ratio. Most utility company websites let you download 12-24 months of billing history as a PDF or CSV. Your annual electricity statement (if your utility provides one) summarizes the full year on one page.

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