Data Check: How Often Do Grid Outages Stop Rooftop Solar Output?

Short answer. If you have a standard grid‑tied rooftop system without backup, every grid outage stops your solar output. This is a safety feature called anti‑islanding. The longer answer adds data. How often this happens depends on local outage hours and how much of that time falls during solar production hours.

In this piece, you will see what triggers solar shutdowns in blackouts, how to size the risk using published reliability data, and how energy storage changes the picture.

Why grid‑tied PV shuts off in blackouts

Anti‑islanding protects line workers

Modern inverters must disconnect from the grid during an outage. This prevents your system from back‑feeding lines that crews think are de‑energized. Safety codes and interconnection standards require this behavior. As the U.S. Department of Energy notes, grid‑tied panels do not keep a home powered in an outage unless the system includes dedicated backup features and transfer equipment. See the DOE explainer: Will Solar Panels Work During a Power Outage?.

What keeps power on

You have three common options:

Hybrid inverter + battery (e.g., LiFePO4). The inverter “islands” your home from the grid and forms a local microgrid within milliseconds to seconds.
All‑in‑one home ESS that integrates battery, hybrid inverter, and PV. Most include an automatic transfer switch and a critical loads panel.
Full off‑grid solar with batteries and a backup generator. This is common for remote sites and is independent of street power.

Grid‑forming and grid‑supporting inverter controls are rapidly maturing. DOE highlights the role of grid‑forming inverters in stable islanded operation and resilience (Grid‑Forming Inverters).

How often do outages stop rooftop solar? A data‑based estimate

Daytime outage overlap with solar production hours infographic

Start with outage hours

Outage impact varies by region and year. In the United States, customers experienced about 5.5 hours of power interruptions in 2022 on average. This includes major events. The Energy Information Administration publishes this reliability figure each year (EIA: Average power interruptions, 2022).

Then look at overlap with solar hours

Rooftop PV only produces during daylight. If outages are spread randomly across the year, only a fraction will overlap with PV production. A simple way to estimate:

Annual hours: 8,760
Hours with daylight PV output: roughly 2,500–4,000, depending on location and season
Share of the year with PV output: ~30%–45%

Using the 2022 EIA average of 5.5 outage hours, the expected overlap that stops rooftop solar is around 1.7 to 2.5 hours per year for a typical home without backup. Local weather, storm seasons, and utility practices can push the value up or down.

Context from grid studies

Grid variability from renewables is a different topic than outage risk. Large systems can handle variable renewable energy (VRE) without big cost spikes by using forecasting and flexible operations, based on field experience summarized by the International Energy Agency (IEA: Getting Wind and Solar onto the Grid). Outages arise from storms, equipment failures, vegetation, and extreme events. Those events pause grid‑tied PV unless you have islanding capability.

What actually stops: output, not sunlight

Energy impact vs. household impact

During an outage, your array still sees sunlight, but the inverter disconnects. Energy that would have been generated in that window is not captured. The household impact is larger than the energy loss. Lights, refrigeration, medical devices, and connectivity go down unless you have storage or a generator. That is why many homeowners pair rooftop PV with a battery to keep critical loads alive.

Safety and compliance still come first

Anti‑islanding is not optional. It is embedded in interconnection rules and codes. DOE consumer materials stress this requirement for worker safety (DOE: Solar and outages). Your design should meet local code, utility standards, and inverter certifications.

Why batteries change the experience

Island mode with a hybrid inverter

With a hybrid inverter and a battery, the system forms a local AC reference. The inverter disconnects from the grid and powers a critical loads panel. PV then charges the battery and runs loads if solar is available. Most residential systems use lithium‑ion chemistries. LiFePO4 stands out for safety and cycle life in home use. IRENA’s market reviews track sharp cost declines and wider adoption of lithium‑ion storage for grid and behind‑the‑meter applications (IRENA: Electricity Storage and Renewables).

How much battery is enough?

Start with critical loads. Refrigeration (80–150 W average), internet/lighting (50–300 W), a few outlets, and a gas furnace blower (300–600 W) often total 0.6–1.5 kW steady, with short peaks higher. A 5 kW hybrid inverter with a 10–15 kWh LiFePO4 battery can cover many homes for an evening outage. Multi‑day storms need more capacity and load discipline. PV production during the day recharges the battery, which extends runtime.

Trends point to more storage

DOI‑backed analysis projects rising storage deployment to integrate high solar shares and strengthen reliability. The U.S. Solar Futures Study outlines significant growth in both utility‑scale and distributed storage to support high PV grids (DOE: Solar Futures Study).

Estimating your risk and sizing a solution

Use local reliability data

Ask your utility for SAIDI (total outage minutes) and SAIFI (outage events) and note major event exclusions. Multiply SAIDI by the share of annual hours with daylight to estimate hours per year that your rooftop solar would be forced off without backup. Add a margin for storm seasons if your area sees clustered outages.

Design checkpoints that matter

Inverter type: choose a hybrid unit with certified islanding and rapid transfer for a backup design.
Battery chemistry: LiFePO4 for stable performance, thermal safety, and long cycle life in residential ESS.
System integration: UL 9540‑listed ESS, correct overcurrent protection, and a dedicated critical loads subpanel.
PV power vs. inverter rating: ensure PV array can cover daytime loads and recharge the battery in typical sun hours.
Controls: frequency‑watt and volt‑VAR functions improve stability in island mode; many modern inverters support these features.
Backup generator port: in storm‑prone regions, a generator input can extend autonomy in long outages.

Configuration	Outage behavior	Typical transfer time	Can run PV during blackout?	Best use case
Grid‑tied PV only	Inverter shuts down; home loses power	N/A	No	Lowest upfront cost; areas with very few outages
Hybrid inverter + LiFePO4 battery (home ESS)	Islanded microgrid powers critical loads; PV recharges battery	~10 ms to a few seconds (model‑specific)	Yes	Homes seeking resilience and steady self‑consumption
Off‑grid solar + battery (+ generator)	Fully independent; not affected by grid failures	Continuous	Yes	Remote sites, farms, cabins, or frequent long outages

Realistic expectations during outages

Daytime blackouts

With a hybrid system, PV can carry many daytime loads and fill the battery. Cloud cover reduces output. Plan headroom. A 6–10 kW array gives more flexibility for concurrent loads and recharging.

Nighttime blackouts

The battery does all the work. Size storage for your hours‑to‑cover goal. Two 10 kWh LiFePO4 packs often cover one night for a typical critical loads panel. Add more if you need heat pumps or well pumps.

Storm clusters and extreme events

Average outage hours can hide risk. A year with 5.5 hours might include a single 6‑hour storm event. In that case, the impact is not “average.” If your area faces hurricanes or ice events, design for a multi‑day profile. IEA’s system operations guidance notes that flexible scheduling and forecasting help at the grid scale, but local resilience still needs on‑site resources (IEA: Grid integration manual).

Product choices that align with resilience goals

LiFePO4 batteries

LiFePO4 batteries pair safety with long cycle life and stable power delivery. They hold up well across many partial cycles, which suits daily solar charging and occasional deep discharges in outages. IRENA highlights that battery storage has rapidly improved in cost and performance, strengthening its role in both grid services and behind‑the‑meter backup (IRENA: Storage costs and markets).

Integrated home ESS

All‑in‑one systems combine a hybrid inverter, battery pack, and system controller. Many include fast transfer to a critical loads panel and app‑based energy management. This reduces integration effort and speeds commissioning. It also simplifies compliance with UL 9540 and rapid shutdown requirements.

Off‑grid solutions

For remote homes, farms, and cabins, off‑grid solar with LiFePO4 storage and a generator set can provide full independence. An off‑grid inverter forms the local AC at all times. This avoids grid outages entirely. It does require careful design for seasonal sun and generator fuel planning.

Data sources and what they imply

EIA’s reliability figures help you estimate outage overlap with daylight. Lower SAIDI means fewer hours your PV would be forced off (EIA reliability data).
DOE’s consumer and research pages explain why PV disconnects and how grid‑forming inverters and storage maintain power during outages (DOE outage explainer; DOE grid‑forming inverters).
The Solar Futures Study shows rising roles for distributed storage and flexible loads in high‑solar grids, improving both integration and resilience (DOE: Solar Futures Study).
IEA synthesis indicates that VRE variability can be managed at scale with modern operations. That keeps the focus on outage resilience at the home level, where batteries make the difference (IEA grid integration).

Bottom line

Grid outages stop standard grid‑tied rooftop solar every time. Based on national averages, only a slice of annual outage hours land in daytime, so the direct energy loss is modest. The household impact is not. If you need lights, refrigeration, and connectivity during blackouts, add a battery and a hybrid inverter. For remote or outage‑prone areas, size storage for multi‑day events and consider an integrated ESS or off‑grid design.

We build lithium batteries, hybrid inverters, and complete ESS for homes and small sites. The goal is simple: reliable, scalable power that keeps your critical loads on, day and night.

Anern Expert Team

With 15 years of R&D and production in China, Anern adheres to "Quality Priority, Customer Supremacy," exporting products globally to over 180 countries. We boast a 5,000sqm standardized production line, over 30 R&D patents, and all products are CE, ROHS, TUV, FCC certified.