Does a 3 kW Solar System Work During a Power Cut? 5 kWh Battery Backup Explained for Jaipur Homes
A 3 kW rooftop solar system can reduce electricity bills, but it does not automatically supply power during an outage. Jaipur homeowners need to distinguish on-grid solar, hybrid solar and battery storage. The right question is how much electricity is needed during a power cut, for how long, and which equipment safely supplies it.
Why Does Normal Rooftop Solar Stop During a Power Cut?
Conventional grid-connected inverters synchronise with the electricity grid and normally disconnect when the grid fails to prevent unintended islanding and protect utility personnel. Even bright sunshine does not make ordinary on-grid solar an outage-backup system. Solar generation and backup are separate capabilities.
On-Grid, Hybrid and Off-Grid Solar Explained
On-grid solar is primarily designed for bill reduction and normally has no backup capability. Properly configured hybrid systems coordinate panels, batteries and grid supply and may operate a dedicated essential-load output during outages. Off-grid systems operate independently and require appropriately designed energy storage or alternative supply. Not every inverter marketed as hybrid has the same backup features.
3 kW and 5 kWh Measure Different Things
Kilowatts (kW) measure power. Kilowatt-hours (kWh) measure energy. A 3 kW solar array is rated for 3 kW DC under standard test conditions; actual output varies. A 5 kWh battery has nominal stored energy, but actual usable AC output is lower after discharge restrictions and conversion losses. Its instantaneous output is constrained by inverter and battery discharge ratings.
How Many Hours Will a 5 kWh Battery Last?
Assume a nominal 5 kWh battery, 90% permitted depth of discharge and 90% AC conversion efficiency. Approximate delivered energy is 5 × 0.90 × 0.90 = 4.05 kWh. At 250 W average load, idealised runtime is 16.2 hours; at 500 W, 8.1 hours; at 600 W, 6.75 hours; at 1,000 W, 4.05 hours; and at 1,500 W, 2.7 hours. These are examples, not guaranteed runtimes; real standby losses, load variation and equipment restrictions matter.
Essential Household Loads: Worked Example
Assume two fans use 140 W, six LED lights 54 W, Wi-Fi 15 W and a refrigerator averages 100 W: total 309 W. A 4.05 kWh usable-energy assumption implies approximately 13.1 hours of idealised backup. Refrigerator starting current and intermittent operation matter. Homeowners should request a measured load survey rather than relying on a salesperson's promised runtime.
Can a 5 kWh Battery Run an Air Conditioner?
Possibly, if the inverter and battery can deliver the required running and starting power. If AC plus other loads average 1.8 kW, the illustrative runtime is 4.05/1.8 = 2.25 hours before additional real-world effects. AC consumption varies by temperature, compressor operation and thermostat settings. Energy capacity alone does not establish whether the system can start the appliance.
Will Solar Recharge the Battery During a Grid Outage?
This depends on system architecture and configuration. Some hybrid systems can continue solar charging in backup mode; others cannot, or require sufficient battery state of charge. Ask the installer to demonstrate islanded operation, solar charging, transfer behaviour, maximum backup load and recovery after battery depletion.
Can I Add a Battery to an Existing 3 kW System?
Potential options include replacing the inverter with a compatible hybrid model, adding an engineered AC-coupled battery system, or installing separate essential-load backup. Compatibility, anti-islanding protection, metering, wiring and applicable DISCOM procedures must be checked before committing to a retrofit. A battery is not automatically plug-and-play with an existing grid-tied inverter.
Is Battery Storage Financially Worthwhile?
Distinguish bill savings from resilience value. Suppose 4.5 kWh of daytime solar could otherwise be exported; after conversion, 4.05 kWh supplies evening loads. At a hypothetical ₹7/unit avoided purchase value, benefit is ₹28.35. If the forgone export value is ₹3/unit, the opportunity cost is ₹13.50 and incremental benefit ₹14.85/cycle. At 300 equivalent cycles, that is ₹4,455/year. A hypothetical ₹1 lakh incremental investment would take over 22 years to recover from this single benefit, excluding degradation and financing. These are NOT Rajasthan tariff quotations. Actual economics depend on the consumer's metering and settlement rules; when exports receive equivalent value, energy shifting may provide little benefit.
PM Surya Ghar Subsidy and Battery Questions
Under current central residential rooftop solar CFA, eligible systems receive ₹30,000 at 1 kW, ₹60,000 at 2 kW and ₹78,000 at 3 kW or more, subject to scheme conditions. This is not a separate guaranteed battery subsidy. Conventional eligible on-grid residential solar does not have a universal battery requirement. Future PM Surya Ghar 2.0 ideas must not be presented as notified rules. Check current MNRE and DISCOM requirements before ordering equipment.
Battery Safety and Installation Checklist
Assess chemistry, battery management system, overcurrent and isolation protection, inverter compatibility, thermal management, environmental exposure, maintenance access and manufacturer installation conditions. Request written usable capacity, discharge rating, warranty, cycle/calendar life, certifications, operating temperature range and service terms. A warranty does not guarantee original battery capacity forever.
Five Questions to Ask Before Buying
Which appliances remain powered? What is the measured average and peak backup load? Can solar recharge the battery during a grid outage? What is the fully installed retrofit cost? What happens if the battery fails after several years? Require a written technical proposal and commissioning demonstration.
Frequently Asked Questions
Does 3 kW solar work during a power cut?
Conventional on-grid solar normally disconnects; a suitably engineered backup arrangement is required.
How long will a 5 kWh battery last?
It depends on usable energy and load. Under the stated assumptions, 500 W averages approximately 8.1 idealised hours.
Can a 5 kWh battery run an AC?
Sometimes, if both instantaneous output and energy capacity are sufficient; actual runtime may be short.
Can I add a battery later?
Possibly, subject to inverter compatibility, safety design and relevant approvals.
Is a battery mandatory under current PM Surya Ghar?
No universal battery requirement applies to ordinary eligible on-grid residential rooftop solar.
Does hybrid always mean backup?
No. Verify the inverter model's actual backup output and operating configuration.
Conclusion: Size Backup for Your Actual Needs
A homeowner needing fans, lights, refrigeration and Wi-Fi backup has different requirements from one wanting multiple ACs during outages. Wattscore recommends measuring essential loads and assessing compatibility, safety and true project economics before buying storage. Contact Wattscore Energy in Jaipur for a rooftop solar and battery-backup assessment.