Portable solar recharge
How much solar actually changes an outage plan?
Panel nameplate watts are not daily energy. The station input limit, usable sunlight, field conditions, and the load schedule decide whether solar meaningfully extends runtime.
Start with accepted watts, not purchased watts
A station cannot accept more solar power than its input allows. The calculator therefore uses the lower of the array nameplate total and the station's solar-input limit:
Accepted solar W = lower of panel W or station input limit WAn 800 W array connected to a 400 W input is modeled at 400 W. The extra nameplate capacity might help under weaker light in some supported configurations, but it does not turn a 400 W input into an 800 W input. Voltage, current, connector, polarity, and array configuration still have to comply with both current manuals.
Convert accepted watts into daily energy
Backup Power Finder uses an editable field-yield percentage to keep angle, heat, cloud, cable, controller, and charging losses visible:
Daily solar Wh = accepted W × peak sun hours × field yield| Scenario | Accepted W | Sun hours | Yield | Modeled Wh/day |
|---|---|---|---|---|
| 200 W portable panel | 200 | 4.0 | 70% | 560 |
| 400 W array | 400 | 4.0 | 70% | 1,120 |
| 400 W array, 300 W station cap | 300 | 4.0 | 70% | 840 |
The 70% default is a planning heuristic, not a product guarantee or weather forecast. NREL's PVWatts can provide location and historical-weather context for fixed PV, but it does not certify the output of a portable panel placed in a yard during a particular outage.
Model at least three sunlight cases
A single sunny-day estimate hides the risk. Use a limited-sun case, a planning case, and a strong-sun case. The calculator provides 2.5, 4.0, and 5.5 peak-sun-hour shortcuts, but those are scenarios—not promises about tomorrow.
- Limited sun: Does the battery still cover the critical overnight load?
- Planning day: Does solar extend runtime enough to matter?
- Strong sun: Does the station input cap strand additional panel capacity?
Pass the compatibility gate before connecting panels
- 1Input voltage range
Confirm that the full array stays within the station's supported input range in the intended configuration.
- 2Maximum current and power
Read the station input specification and the panel's current ratings; do not infer compatibility from watts alone.
- 3Connector and polarity
Use the approved connector path and verify polarity. Similar-looking connectors are not proof of compatibility.
- 4Series or parallel limits
Follow the current manuals for the exact station, panels, and adapters. Do not improvise an array from generic internet diagrams.
The buy-nothing outcome
If the existing panel covers the daily deficit in the limited and planning cases, more panel capacity may add little value. If the station input is already capped, buying more nameplate watts does not raise the modeled accepted watts.
If solar still misses, decide whether the better move is reducing daily load, adding compatible panel capacity, or adding stored energy for weak-weather days. Those are different purchases.
Model a solar scenario →Source register