Compare solar and battery savings using timestamped hourly or 15-minute CSV data, seasonal import/export rates, inverter power, reserve and efficiency.
Quick answer
Interval bill = sum(import kWh x import rate - export kWh x export credit); battery dispatch is limited by stored energy, inverter power and household demand.
Notes updated 2026-10-07
- Best for
- Homeowners pressure-testing solar proposals before signing.
- Inputs needed
- electric usage, local rate, system size or quote assumptions
- Formula used
- Interval bill = sum(import kWh x import rate - export kWh x export credit); battery dispatch is limited by stored energy, inverter power and household demand.
- Method references
- System Advisor Model
How should I compare solar under time-of-use rates?
Read the current rate schedule for your account. Quick mode uses representative profiles and a 4 PM peak-window start. For actual seasonal and weekday pricing, upload timestamped readings with applicable prices in the full-year CSV mode. Neither mode reproduces demand charges, taxes, annual credit banking or gross-production credit settlement.
What does the battery comparison include?
Stored energy comes only from solar surplus. Charging losses, capacity, power and demand limit dispatch. Compare the added energy value against installed battery cost, reserve requirements and warranty limits before estimating payback.
How does this time of use solar estimate work?
Interval bill = sum(import kWh x import rate - export kWh x export credit); battery dispatch is limited by stored energy, inverter power and household demand.
A worked example with explicit assumptions
One surplus kWh stored at 90% efficiency delivers 0.9 kWh. At $0.40 avoided import and $0.06 foregone export, its benefit is 0.9 x $0.40 - $0.06 = $0.30 before battery costs.
What should I verify before using the result?
The quick mode uses representative profiles. CSV mode uses actual timestamped inputs, flags partial periods, and models fixed charges per represented month. Both use net billing; demand charges, taxes, credit banking and Value of Solar settlement are excluded.
Use your bill or written equipment quote, run a conservative scenario, and compare the result with the same inputs in another model.
References and next steps
Calculation notes updated 2026-10-07. Reference links explain the method; they do not establish a current utility tariff or installer price.
Read the full methodology or save and compare your solar plan.
Pressure-test the estimate
Treat the result as a planning range, not a promise. Re-run it with a lower and higher production estimate, your actual utility tariff, and the written installer quote.
- Check roof shade, orientation, tilt, and equipment losses.
- Separate cash price, financing fees, battery cost, and roof work.
- Verify export credits, fixed charges, and interconnection rules.
- Confirm incentive eligibility, deadlines, and tax treatment.
Sources behind this estimate
Use the method references below to check the formula and its limitations. Input defaults and illustrative scenarios are not current tariffs, guaranteed output or live installer quotes.
Utility export rates, eligibility rules, and installer pricing can change. Confirm the applicable tariff, interconnection requirements, and tax treatment before making a purchase decision.
Frequently asked questions
Can I use a year of 15-minute utility readings?+
Yes. CSV mode accepts consecutive hourly, 30-minute or 15-minute interval-start timestamps with explicit UTC offsets. Include load and generation in kWh per interval and the import/export price for each timestamp. It rejects gaps and duplicates instead of filling them.
Does the simulator reproduce FPL net metering or Austin Value of Solar?+
No. It models interval net billing, not banked annual kWh credits or credits on all gross solar production. The utility guides explain these differences. Do not use a single export price to substitute for the account settlement rules.
Does a large peak-to-off-peak spread guarantee battery payback?+
No. Available solar surplus, evening load, inverter power, reserve, efficiency, degradation, installed cost and foregone export credits all matter. The simulator reports energy-bill benefit, not a guaranteed investment return.
How do I use the time of use solar calculator?+
Start with your actual usage, equipment or quote inputs, keep the displayed units, and change one assumption at a time. The quick mode uses representative profiles. CSV mode uses actual timestamped inputs, flags partial periods, and models fixed charges per represented month. Both use net billing; demand charges, taxes, credit banking and Value of Solar settlement are excluded.
What calculation does this tool use?+
Interval bill = sum(import kWh x import rate - export kWh x export credit); battery dispatch is limited by stored energy, inverter power and household demand.
Can I check the arithmetic with an example?+
One surplus kWh stored at 90% efficiency delivers 0.9 kWh. At $0.40 avoided import and $0.06 foregone export, its benefit is 0.9 x $0.40 - $0.06 = $0.30 before battery costs.
What could change the accuracy of my result?+
The quick mode uses representative profiles. CSV mode uses actual timestamped inputs, flags partial periods, and models fixed charges per represented month. Both use net billing; demand charges, taxes, credit banking and Value of Solar settlement are excluded.
Can I use the estimate outside the United States?+
Physical kW and kWh calculations use the same units internationally. Dollar results, regional defaults, emissions factors, incentives and utility guidance are US-oriented. Replace rate and production assumptions with local values; do not apply US tax or export rules abroad.
Can I print or save results without registering?+
Use Print / PDF to save this page from your browser without an email address. The solar plan stores supported scenario inputs in your browser; private files should be checked and redacted before uploading for extraction.
Compare the decision, not just the number
Compare cash, loan, lease, and battery scenarios using the same production, rate, and quote assumptions before choosing a financing path.