Can this solar array carry the loads and refill the battery?
Model both jobs: supplying ongoing outage use and recovering the battery energy already consumed.
Solar must support today's loads before it can restore yesterday's energy
If the array produces 4 kWh per day while the home consumes 3 kWh, only 1 kWh remains to refill the battery. A system that slows battery depletion is useful, but it is not the same as a self-sustaining recovery plan.
Use seasonal sun data
An annual average can overstate winter or storm-season recovery. Use the local month or season that matches the outage risk you are planning around.
Separate efficiency from availability
Efficiency covers equipment and conversion losses. Solar availability is an additional planning allowance for weather and uncertain outage production.
Respect the complete PV input envelope
Maximum watts alone are not enough. Panel-string voltage, cold-weather open-circuit voltage, current, connector rules, and controller limits must all be compatible.
Solar recharge formula
Daily recovery goal = ongoing daily load + (battery deficit ÷ target days)
Required array = daily recovery goal ÷ peak sun hours ÷ efficiency ÷ solar availability
Expected production = accepted array watts × peak sun hours × efficiency × availability
Net battery recovery = expected production − ongoing daily load
Three materially different solar outcomes
Production is below daily load
The battery still loses energy each day. Solar extends runtime but does not create a sustainable outage balance under the entered assumptions.
Production roughly matches daily load
Solar may maintain the battery near its current state, but recovery is slow and small changes in weather or demand can reverse the balance.
Production exceeds load and restores deficit
The plan has a positive daily recovery margin. Verify that the actual battery and solar equipment can accept the required power and operate during an outage.
Solar recharge FAQ
Why not calculate recharge time as battery kWh divided by panel watts?
Panels rarely deliver nameplate power for every daylight hour. The home may also consume energy while charging, and controller, wiring, battery, weather, shading, and temperature losses reduce recovery.
What should I enter for peak sun hours?
Use a location- and season-specific planning value from a reputable solar resource. Peak sun hours are an energy-equivalent measure, not simply the number of daylight hours.
Can I install more panel watts than the battery's solar-input rating?
Some systems permit panel oversizing within strict voltage, current, and configuration rules; others do not. The calculator only flags the watt relationship. Follow the equipment documentation and qualified design requirements.