What Happens to My Solar Panels During a Power Outage?
The short answer: Without a battery, your solar panels shut off during power outages—even when the sun is shining. This surprises many homeowners who assume solar means automatic backup power. It's a safety requirement, not a flaw. Here's why it happens, and how to get actual backup power with solar + battery.
Why Solar Alone Shuts Off During Outages
The Safety Reason: Preventing Electrocution
When the grid goes down, utility workers repair damaged lines. If your solar panels kept sending electricity into the grid, workers could be electrocuted by "backfeed."
To prevent this, all grid-tied solar systems include anti-islanding protection—automatic shutoff when grid power is lost.
How It Works:
- Normal operation: Your inverter syncs with grid frequency (60 Hz)
- Outage detected: Inverter senses grid loss within milliseconds
- Automatic shutoff: Inverter disconnects immediately
- Your panels: Stop producing usable electricity
- Grid restored: Inverter reconnects automatically (usually within minutes)
This isn't a design flaw—it's a legally required safety feature.
The Frustrating Reality
Scenario: It's 2 PM on a sunny day. A car hits a power pole. Grid goes down.
What you expect: "I have solar panels! I'm fine!"
What actually happens: Your lights go out just like everyone else's.
Your panels are soaking up sunshine, but that energy has nowhere safe to go. The inverter keeps it from flowing—protecting workers and preventing damage.
The irony: You're generating free electricity and can't use any of it.
The Solution: Solar + Battery
A battery system with backup capability lets you use solar during outages.
How It Works:
- Outage detected: System disconnects from grid (same as before)
- Battery activates: Inverter switches to "island mode"
- Your home: Runs on battery power
- Your panels: Continue producing, charging the battery
- Self-sustaining: As long as sun shines and battery has capacity, you have power
What You Can Run:
Depends on battery size and your loads:
| Battery Size | Backup Capability |
|---|---|
| 10 kWh | Essentials (fridge, lights, phones) for 12-24 hours |
| 13.5 kWh | Essentials + some comfort for 12-24 hours |
| 27 kWh | Most of home for 12-24 hours; essentials for 2-3 days |
| 40+ kWh | Whole home including AC for extended periods |
The Solar Recharge Advantage:
With solar panels feeding the battery:
- Daytime: Panels recharge battery + power home
- Nighttime: Battery powers essentials
- Next day: Solar recharges battery again
You can theoretically run indefinitely with enough battery and sunshine.
Types of Backup Systems
1. Whole-Home Backup
What it does: Powers your entire home, including large loads like AC.
Requirements:
- Large battery bank (27-40+ kWh)
- Appropriately sized inverter (10-15 kW)
- Potentially electrical panel upgrades
Cost: $25,000-$50,000 installed (before incentives)
Best for: Those who want zero compromise during outages.
2. Essential Loads Backup
What it does: Powers a subset of circuits you designate as essential.
Typical essential loads:
- Refrigerator
- Some lights
- Phone/device charging
- Internet/router
- Garage door
- Medical equipment
Requirements:
- Standard battery (10-15 kWh)
- Essential loads subpanel
Cost: $12,000-$20,000 installed (before incentives)
Best for: Most homeowners—covers critical needs at reasonable cost.
3. Portable Battery (Limited)
What it does: Provides backup for small devices only.
Examples: Goal Zero, Jackery, EcoFlow portable units
Limitations:
- Can't power home circuits
- Limited capacity (1-3 kWh typical)
- Must be manually managed
Best for: Camping, small electronics—not whole-home backup.
California Outage Reality
Public Safety Power Shutoffs (PSPS)
California utilities intentionally shut off power during high fire-risk conditions:
Recent PSPS impact:
- 3+ million customers affected annually
- Some shutoffs lasting 2-4 days
- Little warning before shutoffs
- Most common: October-November
Areas most affected:
- Wildland-urban interface
- Mountainous regions
- High-wind corridors
- Parts of Inland Empire, Sierra foothills, wine country
Weather-Related Outages
Beyond PSPS:
- Heat waves strain the grid (rolling blackouts)
- Storms damage infrastructure
- Equipment failures
- Traffic accidents
Medical Baseline Considerations
If you have life-sustaining medical equipment:
- Utilities provide advance PSPS notification
- You're prioritized for restoration
- But you're NOT exempt from outages
Battery backup is critical for medical equipment users.
How Much Battery for Outage Protection?
Calculate Your Needs:
Step 1: Identify Essential Loads
| Appliance | Watts | Hours/Day | Daily kWh |
|---|---|---|---|
| Refrigerator | 150 | 8 (cycling) | 1.2 |
| LED lights (10) | 100 | 5 | 0.5 |
| Phone charging | 20 | 3 | 0.06 |
| Laptop | 50 | 4 | 0.2 |
| Router | 10 | 24 | 0.24 |
| TV | 100 | 4 | 0.4 |
| Total | 2.6 kWh/day |
Step 2: Determine Outage Duration
| Duration Target | Battery Needed |
|---|---|
| 8-12 hours | 5-8 kWh |
| 24 hours | 10-15 kWh |
| 48 hours | 15-20 kWh |
| Extended (with solar recharge) | 13-15 kWh + solar |
Step 3: Add Buffer
Batteries shouldn't be drained to 0%. Add 20-30% buffer.
For essentials through a 24-hour outage: 10-15 kWh battery is sufficient.
What About Generators?
Generators are another backup option. Here's how they compare:
| Feature | Battery | Generator |
|---|---|---|
| Automatic start | ✅ Instant | ⚠️ Seconds to minutes |
| Noise | ✅ Silent | ❌ Loud |
| Fuel needed | ✅ No (solar recharges) | ❌ Yes (gas, propane) |
| Maintenance | ✅ Minimal | ❌ Regular |
| Indoor safe | ✅ Yes | ❌ No (CO risk) |
| Upfront cost | Higher | Lower |
| Ongoing cost | Lower | Higher (fuel) |
| Lifespan | 15-20 years | 10-15 years |
Hybrid Approach:
Some homeowners use both:
- Battery for instant backup and daily TOU shifting
- Generator for extended outages (multi-day events)
Existing Solar + Adding Battery
If you already have solar without a battery:
Retrofit Options:
1. AC-Coupled Battery
- Works with any existing inverter
- Easier installation
- Slightly less efficient
2. DC-Coupled Battery
- May require inverter replacement
- More efficient
- Better for new systems
Cost to Add:
- Battery + installation: $10,000-$18,000
- After 30% tax credit: $7,000-$12,600
- SGIP rebate: Additional $1,500-$3,000 savings
Timeline:
- Permitting: 2-4 weeks
- Installation: 1 day
- Inspection: 1-2 weeks
The Bottom Line on Outages
Without Battery:
- Solar panels shut off during outages
- You have no power, same as non-solar neighbors
- This is a safety feature, not a defect
With Battery:
- Instant, automatic backup
- Solar recharges battery during day
- Can sustain for days with proper sizing
For California Homeowners:
- PSPS events are increasing
- Grid reliability is decreasing
- Battery backup is becoming standard
Key Takeaways
- Solar alone doesn't provide backup power due to safety requirements
- Battery systems enable backup by creating an isolated "island"
- 10-15 kWh batteries handle essential loads for most homes
- Solar + battery = indefinite backup with daytime recharging
- California outages are increasing with PSPS and grid strain
- Adding a battery later is possible but costs more than installing together
Frequently Asked Questions
Why can't solar panels work during an outage without a battery?
Safety. Without a battery and special inverter, solar would backfeed into the grid, potentially electrocuting repair workers. Grid-tied systems must shut off automatically.
Can I just disconnect from the grid during an outage?
No. Standard inverters can't operate without grid reference. You need a battery system with "island mode" capability.
How fast does battery backup kick in?
Milliseconds. Modern systems detect outages and switch to battery so fast that computers don't reboot and clocks don't reset.
Can I run my AC on battery during an outage?
It depends on battery size. AC units draw 3,000-5,000 watts. A single 13.5 kWh battery can run AC for a few hours; multiple batteries extend this significantly.
What if the outage lasts longer than my battery?
With solar panels, your battery recharges during sunny daytime hours. You can cycle through multiple days by conserving overnight and recharging during the day.
Do I need to do anything when the power goes out?
No. Battery backup systems activate automatically. You may want to reduce usage to extend backup duration, but no manual intervention is required.
Get Backup Power for Your Home
Don't get caught powerless during the next outage.
Find out what battery setup you need:
- Essential loads analysis
- Battery sizing recommendation
- Cost with incentives
- Installation timeline
[Get Your Free Quote] | [Check Battery Options]
Silva Bros Solar: Keeping California homes powered through any outage.
