Solar Electricity Bill Savings Calculator

How this calculator works

The Solar Electricity Bill Savings Calculator computes the immediate monthly bill reduction when a residential PV system replaces grid imports. It is a side-by-side comparison: today’s bill vs. tomorrow’s bill, in dollars per month, using your real utility rate and a realistic estimate of how much solar production your home consumes directly.

Plug in eight numbers and the tool returns your monthly production (kWh), your new monthly bill, your monthly $ saved, and your annual $ saved:

1. Current monthly bill — what you pay today on average. Pull a 12-month total from your utility’s online portal and divide by 12.
2. Monthly usage (kWh) — same source. The U.S. residential average per EIA is 893 kWh/month (2024 data); homes in TX/AZ/FL run 1,100-1,300 kWh, while homes in WA/CA run 600-800 kWh.
3. System size (kW) — the DC nameplate of the PV array. Use the solar panel estimate calculator or how many solar panels do I need to size first.
4. Peak sun hours/day — your local average. NREL’s National Solar Radiation Database (NSRDB) gives 5.5-6.5 in AZ/NV/NM, 4.5-5.5 in TX/FL/CA Central Valley, 3.5-4.5 in the Northeast and Pacific Northwest. Pull the exact number from PVWatts (pvwatts.nrel.gov).
5. Electricity rate ($/kWh) — your blended retail rate, also from your bill.
6. Export rate ($/kWh) — under NEM 1.0/2.0 (most U.S. states), this equals retail. Under NEM 3.0 California, average exports earn 5-8¢/kWh. Under sell-all/buy-all, it equals the utility’s avoided-cost rate.
7. Self-consumption (%) — the fraction of solar energy used directly by your home. 25-40% without a battery, 60-85% with one.
8. Fixed monthly charge — the $8-25 service charge on your bill that doesn’t go away when you go solar.

How the math works

The calculator runs the following sequence of equations:

monthly_kWh_produced = system_kW × peak_sun_hours × 30.4 × 0.77
self_consumed_kWh    = min(monthly_use_kWh, monthly_kWh_produced × self_pct/100)
exported_kWh         = monthly_kWh_produced - self_consumed_kWh
imported_kWh         = monthly_use_kWh - self_consumed_kWh
import_cost          = imported_kWh × retail_rate
export_credit        = exported_kWh × export_rate
new_bill             = max(fixed_charge, import_cost - export_credit + fixed_charge)
monthly_savings      = current_bill - new_bill

The 0.77 multiplier is the IEC 61724 system performance ratio, accounting for inverter losses (3-4%), wire losses (1-2%), soiling (2-5%), high-temperature derating (5-8%), and module mismatch (1-2%). NREL PVWatts uses 0.86 as its DC-to-AC default but applies temperature and soiling separately. Our 0.77 is the conservative integrated number used by most U.S. installers in proposal calculations.

Worked example: 6 kW system in Phoenix

• System: 6 kW DC, 4.5 PSH (Phoenix average per NREL NSRDB)
• Monthly production: 6 × 4.5 × 30.4 × 0.77 = 632 kWh/mo
• Use: 900 kWh/mo (typical AZ home)
• Rate: $0.165/kWh (APS residential blended)
• NEM with 70% self-consumption
• Self-consumed: min(900, 632 × 0.70) = 442 kWh, offsetting $73/mo
• Exported: 632 - 442 = 190 kWh × $0.165 = $31 credit
• Imported: 900 - 442 = 458 kWh × $0.165 = $76 cost
• Plus $12 fixed charge
• New bill: $76 - $31 + $12 = $57/month
• Old bill: 900 × $0.165 + $12 = $160/month
• Monthly savings: $103/month, $1,236/year (64% reduction)

Add a 13.5 kWh Tesla Powerwall and self-consumption climbs to 90%, pushing the new bill toward $20-25 and annual savings toward $1,600.

Per-state retail rates and net-metering rules (Q1 2026)

The biggest driver of your dollar savings is your retail rate. EIA Form 826 February 2026 data:

Rates from EIA Form 826 (February 2026 release). Net-metering rules from DSIRE Q1 2026 update.

The 4× spread between Hawaii ($0.42) and North Dakota ($0.11) means the same 600 kWh/mo of solar offset yields $252/mo of bill reduction in Honolulu but only $66/mo in Bismarck. Always plug your real rate into the calculator — national averages mislead.

Self-consumption strategies that boost monthly savings

Without a battery, the gap between production peaks (10am-3pm) and home demand peaks (6pm-10pm) caps self-consumption around 30%. Three tactics raise it without buying storage:

• Schedule heavy loads on solar. Run dishwasher, washing machine, and EV charging during 11am-3pm. A Level 2 EV charger pulling 7.2 kW for 4 hours absorbs almost 30 kWh of solar. EnergySage data shows scheduling alone lifts self-consumption from 30% to 45-50%.
• Time-of-use rate optimization. If your utility offers a TOU rate, ensure your peak hours align with low solar production. PG&E E-TOU-C charges $0.55/kWh from 4-9pm — every exported kWh during this window is undervalued under NEM 3.0. A small battery just covering 4-9pm dramatically improves bill savings without full backup capacity.
• Heat pump water heater on a timer. A 50-gallon HPWH consuming 1.5 kWh/cycle scheduled for 1pm absorbs almost all solar output. Pairing solar with a HPWH adds 10-15% to self-consumption and a 5-7% additional bill reduction beyond the solar alone.

Federal 30% Investment Tax Credit & state stack

The Section 25D residential clean energy credit gives you 30% of your installed system cost back as a non-refundable federal tax credit (IRS Form 5695, file with your annual return). Effective through Dec 31, 2032 at 30%, then 26% in 2033, 22% in 2034. For a $20,000 system, that’s $6,000 off your federal tax bill — equivalent to dropping payback by roughly 30%.

State-level stacking changes effective monthly cost-of-solar significantly:

• California: SGIP battery rebate $200-1,000/kWh (income-qualified), $0.20/kWh equity tier. NEM 3.0 makes batteries near-mandatory.
• New York: NY-Sun MW Block Program $0.20-0.40/W up-front incentive + 25% state tax credit (capped at $5,000) + property tax exemption.
• Massachusetts: SMART tariff base rate $0.16-0.21/kWh production payment for 10 years, on top of net metering. Battery adder $0.03-0.05/kWh.
• Texas: No state credit but Austin Energy ($2,500), San Antonio CPS ($2,500), and Oncor ($0.40/W) offer utility rebates that often outperform state programs elsewhere.
• New Jersey: SuSI SREC-II program pays $85/MWh for 15 years on top of net metering. Combined with retail-rate NEM, NJ has the highest effective $/kWh in the country.

Always check DSIRE (dsireusa.org) for your ZIP code’s current incentive stack before sizing.

When the new bill is higher than the floor

If your fixed monthly charge is $20 and your import cost minus export credit comes to negative $50, your new bill bottoms out at $20, not -$30. Most utilities credit the surplus to your next month’s bill rather than paying cash; a few (Maine, Massachusetts, Vermont) cash out annually at the avoided-cost rate. Set “fixed monthly charge” to your actual minimum bill (look for “minimum charge” or “customer charge” on a recent bill) for an accurate floor.

Sources

• U.S. Energy Information Administration — Form 826 monthly retail prices, Form 861 annual sales (eia.gov/electricity)
• DSIRE — Database of State Incentives for Renewables & Efficiency, NC State University (dsireusa.org)
• NREL — National Solar Radiation Database (NSRDB) and PVWatts Calculator v8 (pvwatts.nrel.gov)
• IRS Form 5695 — Residential Energy Credits, 2025 instructions
• EnergySage — H2 2025 Solar Marketplace Intel Report
• SEIA — Solar Market Insight Report Q1 2026

For more detail on long-term savings see our 25-year solar panel savings calculator, solar payback period calculator, and federal solar tax credit calculator.

For questions about this tool: contact@solarcalculatorhq.com