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Quick Answer
Standard grid-tied solar shuts off during outages — this is a safety requirement (anti-islanding). Solar + battery keeps your home powered during blackouts. Without a battery, your panels produce nothing during outages. A single battery provides 8–12 hours of essential backup; two batteries cover 24+ hours for most homes.
Your solar panels alone will not keep the lights on during a blackout. Here is exactly how solar + battery backup works, how long it lasts, and what it costs to keep your home powered when the grid goes down.
This is the single most misunderstood fact about residential solar: your solar panels do not work during a power outage. Not because they stop generating electricity — the sun is still shining — but because your inverter deliberately shuts them off.
When the grid goes down, utility workers are sent to repair downed power lines, damaged transformers, and other equipment. If your solar panels continued to push electricity into the grid, those workers could be electrocuted by power flowing from your roof through the neighborhood wires.
The National Electrical Code (NEC) and IEEE 1547 standard require all grid-tied inverters to have anti-islanding protection — the ability to detect a grid outage and immediately disconnect your system. This is not optional. Every solar inverter sold in the US must comply.
Additionally, NEC 2020 requires rapid shutdown — the ability to de-energize conductors within 30 seconds. This protects firefighters who may need to access your roof during an emergency.
The Irony
During a sunny-day power outage, you could be standing under 10 kW of solar panels capable of powering your entire house — and none of that electricity is available to you. This is exactly why battery storage exists: to capture and store that solar energy for use when the grid is down.
A battery storage system fundamentally changes how your solar works during an outage. Here is the two-mode operation.
Key Insight: Solar + Battery = Indefinite Backup
During a multi-day outage, a battery alone eventually runs out. But solar + battery can sustain essential loads indefinitely because the solar panels recharge the battery every day. As long as the sun rises, your essential circuits stay powered. This is why solar + battery is far superior to a generator for extended outages.
How long your battery backup lasts depends on how many batteries you have and how much you use during the outage. Here is the breakdown assuming no solar recharging (worst case: nighttime or cloudy-day outage).
| Battery Config | Essential Only | Moderate Use | Whole Home | Installed Cost |
|---|---|---|---|---|
| 1 Battery (13.5 kWh) | 12-18 hours | 8-12 hours | 4-6 hours | $12,000-15,000 |
| 2 Batteries (27 kWh) | 24-36 hours | 16-24 hours | 8-12 hours | $22,000-27,000 |
| 3 Batteries (40.5 kWh) | 48+ hours | 24-36 hours | 12-18 hours | $32,000-39,000 |
Essential Only
Fridge, lights, internet, phone chargers, sump pump
~3-5 kWh/day
Moderate Use
Essentials + microwave, TV, some lights, well pump
~8-12 kWh/day
Whole Home
Everything including AC, cooking, hot water
~25-40 kWh/day
The key to maximizing battery backup duration is choosing which circuits to back up. Not every appliance needs to run during an outage. Here is how to think about it.
Total essential draw: ~3-5 kWh/day
One battery (13.5 kWh) lasts 12-18 hours at this level.
These drain a battery in 2-4 hours
One AC cycle alone can drain 50%+ of a single battery.
How your battery connects to your home’s electrical system determines what gets backed up and how much control you have. There are three main approaches.
$500-1,000
A secondary electrical panel that includes only the circuits you want backed up. The electrician physically moves select breakers to this panel during installation.
Pros
Cons
Best for: Budget-conscious homeowners who know exactly what they want backed up
$1,500-3,000
Automatically switches between grid power and battery power when an outage is detected. Can back up more circuits than a critical loads panel.
Pros
Cons
Best for: Homeowners who want broader coverage with automatic operation
$3,500-5,000
Replaces your entire electrical panel. Every circuit is individually controllable via app. You can change what is backed up in real time during an outage.
Pros
Cons
Best for: Tech-forward homeowners who want maximum flexibility and data
Many homeowners compare batteries to generators. Here is the honest, side-by-side comparison.
| Feature | Generator | Battery |
|---|---|---|
| Upfront cost | $3,000-8,000 | $12,000-27,000 |
| Fuel cost | $50-100/day | $0 (solar) |
| Maintenance | Oil changes, fuel storage, annual service | Virtually none |
| Noise level | 65-80 dB (lawn mower) | Silent |
| Indoor air quality | Carbon monoxide risk (outdoor only) | No emissions |
| Automatic start | Automatic with ATS ($2K+ extra) | Instant and automatic |
| Daily use benefits | None (emergency only) | TOU arbitrage, demand response revenue |
| Lifespan | 10-15 years (with maintenance) | 15-20 years (warranty-backed) |
| Fuel availability | Depends on supply during storms | Unlimited (sun) |
The Northeast has specific outage risks that make battery backup particularly valuable. Understanding your risk profile helps you size the right system.
Nor'easters
Duration: 1-5 days
Frequency: 2-4 per winter
High riskIce storms
Duration: 1-7 days
Frequency: 1-2 per winter
High riskHurricane season
Duration: 2-7 days
Frequency: 0-1 per year
Medium riskSummer thunderstorms
Duration: 2-8 hours
Frequency: 5-10 per summer
Low risk| State | Avg. Outage Duration | Major Storm Duration | Key Risk |
|---|---|---|---|
| Massachusetts | 4-8 hours | 1-5 days | Nor'easters, aging grid in Boston |
| Connecticut | 4-6 hours | 1-7 days | Ice storms, Eversource infrastructure |
| Rhode Island | 3-6 hours | 1-3 days | Coastal storms, compact grid helps |
| New Hampshire | 6-12 hours | 2-7 days | Rural lines, ice storms, tree damage |
| Maine | 8-18 hours | 3-10 days | Most rural grid in NE, ice storms |
| New Jersey | 3-6 hours | 1-5 days | Coastal flooding (Sandy-type events) |
Our Recommendation for the Northeast
For most New England homeowners, one battery + solar provides sufficient backup for typical outages (4–12 hours). The solar panels recharge the battery during the day, extending backup to cover multi-day events. If you live in a rural area (NH, ME) with longer average outages, or if you have medical devices that must stay powered, consider two batteries for full peace of mind.
No. Standard grid-tied solar panels shut off automatically during power outages. This is a safety requirement called anti-islanding, mandated by NEC (National Electrical Code). It prevents your panels from sending electricity back into the grid while utility workers repair downed power lines. Without a battery, your solar panels produce zero electricity during a blackout.
A single home battery (like Tesla Powerwall at 13.5 kWh) costs $12,000-15,000 installed. Two batteries cost $22,000-27,000. Three batteries cost $32,000-39,000. These prices include the battery, gateway/transfer switch, installation labor, and permitting. State incentive programs like ConnectedSolutions (MA/RI) can offset $1,000-3,000 through demand response revenue.
A single 13.5 kWh battery powers essential loads (fridge, lights, internet, phone chargers) for 12-18 hours. If solar panels recharge the battery during daylight, you can sustain essential loads indefinitely. Two batteries provide 24-36 hours of essential backup without solar recharging, and 48+ hours with solar. Whole-home backup requires 2-3 batteries and lasts 8-18 hours.
It depends on your usage. One battery can power essential loads only (fridge, lights, internet). For whole-home backup including AC, cooking, and hot water, you need 2-3 batteries plus solar panels for daytime recharging. Most homeowners choose a "critical loads" approach: back up the essentials and skip high-draw appliances like AC, dryers, and EV chargers during outages.
A critical loads panel ($500-1,000) is a secondary electrical panel that only includes the circuits you want backed up. An automatic transfer switch ($1,500-3,000) is more sophisticated, automatically switching between grid and battery. A Span smart panel ($3,500-5,000) replaces your entire electrical panel and lets you control every circuit individually via app, choosing what to back up in real time.
Batteries are better for most homeowners. They are silent, start automatically, require zero maintenance, produce no emissions, and generate daily revenue through programs like ConnectedSolutions. Generators are cheaper upfront ($3,000-8,000 vs $12,000+) but require fuel ($50-100/day), regular maintenance, produce noise and carbon monoxide, and provide no daily-use benefits. For multi-day outages, solar + battery is superior because it recharges from the sun.