Solar recharge calculator

How long will a solar panel take to charge a battery?

Calculate charging time from battery watt-hours, panel watts, realistic good-sun hours, losses, and the station's solar-input limit. The result is a planning estimate, not a lab promise.

Quick formula: energy to replace divided by effective charging watts. The effective watts are the lower of panel watts and station input watts, multiplied by the planning efficiency.

Estimated recharge time4 hours

A normal day of clear sun may be enough for this setup.

Inputs

Recharge setup

Power station model, optionalSelecting a model fills the listed capacity and maximum solar-input watts. Verify the current manual before connecting a panel.Power station capacityUse the listed watt-hours. If the battery is listed in Ah, use the amp hours to watt hours calculator first.Panel ratingExample: 100W or 200W portable panel.Power station solar input limitThe station may cap a larger panel.Good sun hours per dayUse realistic strong-sun hours, not daylight hours.Panel collection factorApplied to panel rating before the station's solar input cap.Downstream charge efficiencyApplied after the input cap for controller, battery, and charge-path losses.Starting battery levelSet above zero if the station is partly charged.

Why the estimate changes

Panel angle, shade, heat, clouds, wiring losses, controller behavior, and battery taper can all slow charging. Use the result as a shopping filter, then check the manual.

Current model references

Solar input limits used by the presets

These are manufacturer-listed values, checked on July 16, 2026. Product names can outlive a hardware revision, so use the linked manual or specification page as the final check.

Power station	Capacity	Max solar input	PV voltage range	Source
EcoFlow RIVER 2	256Wh	110W	11-30V	EcoFlow RIVER 2 specifications
EcoFlow RIVER 2 Pro	768Wh	220W	11-50V	EcoFlow RIVER 2 Pro specifications
BLUETTI AC70	768Wh	500W	12-58V	BLUETTI AC70 user manual
EcoFlow DELTA 2	1024Wh	500W	11-60V	EcoFlow DELTA 2 specifications
BLUETTI AC180	1152Wh	500W	12-60V	BLUETTI AC180 specifications

Recharge notes

What the solar recharge estimate is really checking

The useful question is not only whether a panel says 100W or 200W. The station's input limit, realistic sun hours, and charging losses decide whether that panel can actually refill the battery in the time you have.

Input limit

A larger panel can be capped

If the power station only accepts 100W of solar input, a 200W panel may still charge near a 100W-class pace.

Sun hours

Use strong-sun hours

Four to five usable sun hours can be realistic in many places, but shade, season, clouds, and panel angle change the number fast.

Efficiency

Leave room for real losses

Panel collection losses apply before the station's input cap. Controller, battery, and charge-path losses apply after it. The default factors keep those two stages visible.

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