How to Use This Tool
Separate direct solar use, battery-supplied solar, export and grid import for one period. Calculate solar self-consumption ratio, onsite solar use, export and grid import from consistent meter-period energy totals.
The decision this tool supports
Self-sufficiency and self-consumption answer different questions; mixing their denominators makes battery and export performance impossible to compare. This page keeps the decision bounded to solar self-consumption ratio and the supporting outputs shown beside it. Solar Self-Consumption does not import an account, infer a market rate, or silently substitute an industry average.
Inputs and units
The Solar Self-Consumption calculation uses Solar generation, Direct solar use, Battery discharge attributed to solar, Total site consumption. Keep all money values in one currency and all time, distance, mass, energy or volume entries in the unit printed beside the field. Mixing Solar Self-Consumption scopes can produce a plausible number with the wrong meaning.
- Solar generation is entered in kWh.
- Direct solar use is entered in kWh.
- Battery discharge attributed to solar is entered in kWh.
- Total site consumption is entered in kWh.
Formula and worked check
Self-consumption ratio = (direct solar use + solar-attributed battery discharge) ÷ solar generation × 100. 600 kWh generation with 360 kWh direct use and 80 kWh solar-attributed battery discharge gives 73.3% self-consumption, 160 kWh export and 260 kWh grid import. The Solar Self-Consumption default is an executable known-answer case, not a benchmark or recommendation. Change one input and verify that the direction of solar self-consumption ratio still matches the stated relationship.
How to interpret the result
A higher ratio means less generated energy was exported, but it does not by itself prove better economics or lower grid dependence. The additional Solar Self-Consumption outputs expose the denominator, comparison, capacity or reverse value needed to audit the primary result instead of presenting one unexplained number.
Assumptions
- All energy totals cover the same meter period.
- Battery discharge counted here is traceable to solar charging.
- Onsite solar use cannot exceed generation or site consumption.
Save the Solar Self-Consumption input values and date with any material decision. A later Solar Self-Consumption rerun is reproducible only when the same assumptions and units are available.
Limitations and safety boundary
Battery charging losses, grid-charged battery energy, meter timing, curtailment, tariffs and demand charges require a more detailed energy balance. Solar Self-Consumption is an estimate and cannot replace a contract, local code, licensed professional, calibrated measurement, lender statement or platform report where one governs the decision.
Source and privacy
The Solar Self-Consumption definition or rule was checked against NREL — PVWatts Calculator on 2026-08-26. Recheck NREL — PVWatts Calculator when a specification or policy behind Solar Self-Consumption can change. Solar Self-Consumption arithmetic runs in this browser tab; ecech does not receive the values through a calculation API.
Sources & assumptions
Tool Spec v2 · verified 2026-08-26. Platform rules and fees can change; the editable inputs remain authoritative for your account.
Official references
- NREL — PVWatts Calculator (checked 2026-08-26)
Model assumptions
- All energy totals cover the same meter period.
- Battery discharge counted here is traceable to solar charging.
- Onsite solar use cannot exceed generation or site consumption.
- Battery charging losses, grid-charged battery energy, meter timing, curtailment, tariffs and demand charges require a more detailed energy balance.
