Calculator Inputs
Formula Used
The calculator models annual energy step-by-step to show where losses occur.
How to Use This Calculator
- Pick a DC input method: measured daily DC energy, or PV size with yield.
- Enter rated efficiency and your expected average load factor.
- Adjust partial-load penalty, temperature, wiring, and clipping if relevant.
- Set your electricity value per kWh for a financial view of losses.
- Press Calculate, then export results as CSV or PDF.
Example Data Table
| Scenario | DC/day (kWh) | η rated | Load | Temp | AC/year (kWh) | Loss/year (kWh) |
|---|---|---|---|---|---|---|
| Rooftop 5kW | 24.0 | 97.5% | 55% | 35°C | 8,235 | 525 |
| Small hybrid | 10.5 | 96.8% | 45% | 40°C | 3,521 | 312 |
| Commercial | 180.0 | 98.2% | 70% | 30°C | 63,162 | 2,538 |
| Hot climate | 28.0 | 97.0% | 50% | 50°C | 9,352 | 868 |
| Battery backup | 8.0 | 95.5% | 30% | 32°C | 2,651 | 269 |
Interpreting annual DC and AC energy
Start with a measurable baseline: DC kWh per day and operating days. A 24.0 kWh/day system modeled for 365 days produces 8,760 kWh DC annually. The calculator converts that to AC delivered after efficiency and downstream losses. Comparing DC and AC highlights what you pay for, and what actually reaches loads or export meters.
Efficiency changes across average load
Rated efficiency is usually reported near the inverter’s sweet spot. Real operation often averages 30–70% of rated power, especially on partially sunny days. The model applies a quadratic partial-load penalty using load factor. For example, 97.5% rated at 55% load with a 4.0 point penalty can yield an effective 96.7% before temperature and other losses.
Heat derating and seasonal sensitivity
Temperature impacts are expressed as a loss percent per degree above 25°C. With a 0.05%/°C coefficient and an average inverter temperature of 35°C, the temperature loss fraction is 0.50%. Applied after conversion, this can remove 40–50 kWh per 10,000 kWh converted. Hot enclosures and poor ventilation can amplify this effect during peak months.
Benchmark loss ranges for planning
Use planning ranges to sanity-check inputs. Conversion losses typically fall between 1.0–4.5% depending on topology and loading. Wiring and AC-side losses often land near 0.5–2.5% for short residential runs, and 0.5–1.5% for well-designed commercial layouts. Clipping or curtailment can be 0–3% when arrays are oversized or export-limited.
Turning loss kWh into financial decisions
Financial impact is loss kWh multiplied by value per kWh. If annual loss is 320 kWh and electricity value is 0.16 per kWh, the loss cost is 51.20 per year. Use this to compare upgrades: better ventilation, shorter cable runs, or a higher-efficiency inverter. The export files help document assumptions for proposals, audits, or budgeting today carefully documented clearly consistently across projects and teams today carefully documented clearly consistently across projects and teams today carefully documented clearly consistently across projects and teams today carefully documented clearly consistently across projects and teams today carefully documented.
FAQs
Why does load factor change inverter efficiency?
Inverters have fixed overhead and switching losses. At lower average output, those losses represent a bigger share of energy processed. The calculator models this with a partial-load penalty so mid-load performance is reflected in annual results.
What temperature value should I enter?
Use a realistic enclosure or heatsink temperature if available. If you only know ambient, add a small uplift for enclosed installations. The model applies temperature loss only above 25°C, so mild climates may show minimal derating.
How do I estimate clipping or curtailment loss?
Use inverter logs, monitoring portals, or export-limit settings. If you have no data, start with 0.5–1.5% for modest oversizing and export caps. Refine later using measured peak-time power traces.
Is wiring loss separate from conversion loss?
Yes. Conversion loss is inside the inverter when turning DC into AC. Wiring and AC-side loss cover cables, breakers, transformers, and any downstream equipment. Separating them improves the loss breakdown and helps target fixes.
Can I use this for hybrid or battery systems?
Yes for a planning view. Enter DC energy flowing through the inverter stage you want to evaluate, then adjust load factor and clipping assumptions. For detailed round-trip battery modeling, treat charging and discharging as separate runs.
Why do CSV and PDF downloads require a calculation first?
Exports summarize the latest inputs and outputs stored in the current session. Run a calculation so the tool can capture a consistent snapshot. After that, the download buttons generate a file instantly from those stored results.