Path-Q Solar
Can solar savings be estimated accurately if my electricity rates change during the year?
Answer
Yes, but the estimate should use time-specific rates and the system's time-matched production and consumption rather than one annual average. Accuracy is limited by uncertainty in future rates, tariff changes, exports, weather, load changes, and system performance, so a range of outcomes is more credible than a single precise number.
Key points
- Match hourly or period-specific solar output to the rate applying when energy would otherwise be purchased.
- Include seasonal rate changes, time-of-use periods, demand charges, and export compensation where relevant.
- Model multiple future-rate cases and identify which assumptions drive the result.
What it depends on
- Current and historical tariff schedules
- Interval consumption and production profiles
- Export and demand-charge treatment
- Expected future rate and load changes
Risks and trade-offs
- An annual average can misstate savings when high rates occur outside solar-production hours.
- Future tariff changes may either improve or reduce the system's value.
- Precision in the model can create false confidence when the inputs are uncertain.
Information you may need
- Time-varying rate schedules
- Interval utility data
- Monthly or hourly production forecast
- Conservative, central, and high-rate scenarios
Your next step
What to do next
Use a time-matched cash-flow model and ask the provider to show sensitivity to rate and export assumptions.
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