Path-Q Solar
Should I size solar differently if exported electricity is paid less than imported electricity?
Answer
Often, yes. When exported electricity is worth less than imported electricity, the economically preferred system may be sized closer to the load that can be served on-site, unless additional production has sufficient value through future load growth, storage, favorable credits, resilience, or other benefits. The best size requires a time-based comparison rather than an annual energy match alone.
Key points
- Use hourly or interval consumption and production to estimate self-consumption.
- Compare the marginal cost of additional capacity with the lower export value of its expected output.
- Consider future electric loads, battery operation, backup objectives, roof constraints, and program limits.
What it depends on
- Current import and export rates
- Hourly household load and production
- System design and marginal installation cost
- Battery and future-load assumptions
- Utility program caps and tariff changes
Risks and trade-offs
- Undersizing may reduce the opportunity to cover future loads or benefit from later rate changes.
- Oversizing can increase cost while producing energy with relatively low compensation.
- A battery may improve self-consumption but may not justify an otherwise uneconomic system size.
Information you may need
- Current utility tariff and export rules
- Interval electricity use
- Production estimates for several system sizes
- Future load plans and battery pricing
Your next step
What to do next
Request at least two or three system sizes and compare their incremental cost, self-consumed energy, exported energy, and net value under the current tariff.
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