Can Solar + Battery Backup Really Protect an Illinois Home During an Outage? What a New Illinois Shines Case Study Shows

Updated: September 29, 2026 · Estimated read time: 11 minutes

The power goes out.

Your neighbors' houses go dark.

But you have solar panels on your roof.

So your lights stay on... right?

Not necessarily.

One of the biggest misconceptions about residential solar is that solar panels automatically provide electricity whenever the grid goes down.

Most standard grid-connected solar systems shut down during an outage for safety.

To keep using solar electricity when the grid is unavailable, a home generally needs a properly designed solar + battery backup system capable of operating independently from the grid.

A new Illinois Shines case study gives us a real Illinois example of what that can look like.

A Centralia-area household paired solar with four batteries because recurring weather-related outages threatened essential water and heating systems for the family's small farm. Illinois Shines reports that the completed system provided approximately three hours of backup power, helped maintain critical farm operations, and cut the household's monthly electricity bills roughly in half.

But that doesn't mean:

Four batteries = three hours for every home.

Battery backup doesn't work that way.

Let's look at what Illinois homeowners should actually understand before buying storage.

Quick Answer

Solar panels alone generally do not keep a typical grid-connected home powered during a utility outage.

For backup power, the system normally needs:

• Battery storage

• A compatible inverter or power-control system

• Equipment that safely disconnects the home from the utility grid

• A properly designed backup configuration

The battery can then power selected household loads—or potentially a larger portion of the home—depending on:

Battery capacity

Battery power output

Which circuits are backed up

How much electricity those circuits use

How long the outage lasts

Whether solar can recharge the battery during the outage

The most important question isn't:

“How many batteries do I need?”

It's:

“What do I want to keep running, and for how long?”

Table of Contents

1. What happens to solar during a power outage?

2. Why standard solar shuts down

3. What solar + battery changes

4. What the new Illinois case study shows

5. Battery capacity vs. battery power

6. Essential-load vs. whole-home backup

7. How long will a solar battery last?

8. Can solar recharge the battery during an outage?

9. What should you back up first?

10. What about air conditioning and electric heat?

11. Well pumps, sump pumps and rural homes

12. What happens during a multi-day outage?

13. Illinois battery incentives

14. Ameren, ComEd and CWLP differences

15. Questions to ask before buying a battery

16. Frequently asked questions

What Happens to Solar During a Power Outage?

Imagine it's 1 PM.

The sun is shining.

Your rooftop solar system is producing:

7 kW

Then a storm knocks out the utility grid.

Many homeowners assume the house should simply keep using those seven kilowatts.

But with a typical grid-connected solar system:

The solar system shuts down too.

Why?

Safety.

Utility workers may be repairing damaged electrical lines.

If residential solar systems continued pushing electricity onto those lines while utility crews expected them to be de-energized, the situation could become extremely dangerous.

The U.S. Department of Energy explains that residential solar systems generally disconnect when grid power is lost unless the system includes equipment specifically designed to operate independently.

So:

Solar panels ≠ automatic backup power.

What Does a Battery Change?

A properly designed solar + storage system can create an electrically isolated portion of the home during an outage.

You'll sometimes hear this called:

Islanding

The home disconnects from the utility grid while the backup system continues supplying approved household loads.

The energy path might look like:

Solar → Home

and:

Solar → Battery

Then when solar production drops:

Battery → Home

The Department of Energy describes properly configured solar + storage systems automatically detecting a grid outage and switching into an islanded mode so protected loads can continue receiving electricity.

That's fundamentally different from solar alone.

What a Real Illinois Project Shows

Illinois Shines published a new case study on September 21 featuring Gragg Street Farm, a veteran-owned small farm household in Centralia, Illinois.

This is an Illinois Shines case study—not a LuNova customer project.

The household had two major concerns:

Rising electricity costs

and:

Recurring severe-weather outages

The outages were especially important because the property depended on electricity for water, heating and other systems used to care for goats, poultry and rabbits.

Their electricity consumption was substantial:

Approximately 3,000–5,000 kWh per month

and Illinois Shines reports that electric bills could reach approximately:

$1,000 during harsh-weather months.

This wasn't a typical small suburban household.

And that's exactly why the case study teaches an important lesson:

Battery design needs to match the actual loads.

The Centralia Solar + Battery System

According to Illinois Shines, the project included:

40 south-facing solar panels

23.2 kW DC / 15.2 kW AC solar capacity

Approximately 32,000 kWh expected annual solar production

Four batteries

Customer ownership

The ground-mounted system was energized in April 2025. Illinois Shines reports that installation, including weather and utility approval, took approximately three weeks for this particular project.

Again:

That's one project.

It should not be treated as a universal Illinois installation timeline, system size or battery recommendation.

What Happened During an Actual Outage?

Here's where the case study becomes particularly interesting.

Illinois Shines reports that the battery system provided approximately:

Three hours of backup power.

During one recent outage, the surrounding block reportedly lost power for approximately three hours.

The household reported experiencing only about one minute without electricity before the backup system took over, allowing essential water and heat systems for the animals to continue operating.

That's a real example of solar + storage providing resilience.

But don't interpret it as:

“Four batteries always provide three hours.”

Battery runtime depends on what you're powering.

Battery Capacity vs. Battery Power

These are two of the most important numbers in a battery proposal.

And they're frequently confused.

Battery Capacity — kWh

Capacity tells you approximately how much energy the battery can store.

Think of it like the size of a fuel tank.

For example:

10 kWh

13.5 kWh

20 kWh

Battery Power — kW

Power tells you approximately how much electricity the battery can deliver at one moment.

Think of it like how quickly the fuel can flow from the tank.

A battery could have plenty of stored energy but still be unable to operate every major appliance simultaneously.

That's why both numbers matter.

If your proposal simply says:

“1 battery included”

that's not enough information.

Our complete LuNova Solar Battery in Illinois guide explains these differences in greater detail.

How Long Will a Solar Battery Last During an Outage?

There is no honest universal answer.

The simplified concept is:

Usable battery energy ÷ household load = approximate runtime

Imagine a battery has roughly:

10 kWh of usable energy.

If your protected household loads average:

1 kW

the theoretical runtime could be around:

10 hours

before accounting for system losses, reserve settings and other factors.

But if your home is pulling:

5 kW

that same stored energy could disappear far more quickly.

That's why asking:

“How many hours does this battery last?”

without discussing the loads is like asking:

“How far will this tank of gas take me?”

without knowing the vehicle or driving conditions.

ESSENTIAL LOADS MATTER

Thinking about solar + storage?

Start by deciding what must stay powered during an outage.

CHECK MY HOME

A useful battery design should consider your home's actual loads, your utility, solar production, backup priorities and future electricity needs—not simply add a battery because it's available.

Battery runtime, backup capability, solar recharge, incentives and system performance vary by equipment, design, weather, household loads and utility requirements.

Essential-Load Backup vs. Whole-Home Backup

This distinction can dramatically change the battery system you need.

Essential-Load Backup

The battery might support only selected circuits such as:

• Refrigerator

• Freezer

• Lights

• Wi-Fi

• Phone charging

• Garage-door opener

• Medical equipment

• Sump pump

• Well pump

• Selected outlets

This reduces the amount of electricity you're asking the battery to provide.

That can extend runtime.

Whole-Home Backup

A larger backup configuration may attempt to support much more of the house.

That could include:

• HVAC

• Kitchen appliances

• Water heating

• Laundry

• More outlets

• Additional major loads

But:

“Whole-home backup” does not mean unlimited electricity.

A home can still demand more power than the batteries can provide.

Battery capacity remains finite.

Solar production remains weather-dependent.

Why Air Conditioning Can Change Everything

Consider a summer outage.

Your refrigerator might use relatively modest power.

Your lights might use even less.

Then the central air conditioner starts.

Suddenly household power demand can increase substantially.

That's why a battery that could theoretically support essential loads for many hours may provide much shorter backup when running:

Central AC

Electric resistance heat

Electric water heating

An electric dryer

or:

EV charging

Large loads matter.

Should You Charge Your EV During a Blackout?

Usually, EV charging should be considered carefully when preserving limited backup energy.

An EV charger can represent a major electrical load.

During an extended outage, you may prefer the battery's stored energy to support:

Refrigeration

Sump pump

Water

Lights

Internet

and:

Heating controls

rather than sending a large amount of energy into the car.

A properly designed system can prioritize loads based on the homeowner's goals.

Rural Homes May Have Different Priorities

The Centralia case study is especially useful here.

For that household, maintaining:

Water

and:

Heat for livestock

wasn't optional.

A suburban homeowner might instead prioritize:

Sump pump

Refrigerator

Medical equipment

Internet

Garage door

or:

HVAC

Another rural home may have:

A well pump

which could be one of the most important backup loads.

There isn't one universal:

“Battery backup package.”

There are homeowners with different needs.

Can Solar Recharge the Battery During an Outage?

Potentially, yes.

But the system has to be designed for it.

A properly configured solar + battery backup system may continue using solar production while disconnected from the utility grid.

During daylight:

Solar → Home

and:

Solar → Battery

At night:

Battery → Home

Then the next sunny day may recharge the battery.

This is one of the biggest differences between battery storage and a backup source that depends entirely on stored fuel.

DOE notes that solar coupled with storage can continue providing power during extended outages without requiring fuel deliveries, provided sufficient sunlight, storage and proper system configuration are available.

But there is an important limitation.

Solar Cannot Recharge What the Weather Doesn't Produce

Imagine a multi-day outage during:

Heavy cloud cover

A winter storm

or:

Snow-covered panels.

Solar production may be dramatically reduced.

Your battery doesn't create energy.

It stores energy.

So the backup plan should not assume:

“The battery will just recharge every day.”

Maybe it will.

Maybe it won't.

The system should account for realistic weather and load scenarios.

Our guide to solar panels in Illinois winter weather explains why seasonal production can vary substantially.

What Happens During a Multi-Day Outage?

This is where household behavior becomes extremely important.

Suppose you begin an outage with:

100% battery charge.

Day one:

You continue using the house normally.

Air conditioning runs.

Laundry runs.

The oven runs.

The EV charges.

Battery energy can disappear quickly.

Now imagine instead that you switch into:

Backup mode.

You reduce discretionary loads.

You preserve energy for:

• Refrigerator

• Freezer

• Water

• Sump pump

• Lights

• Communications

• Essential heating/cooling

• Medical needs

Then solar recharges part of the battery the following day.

The same battery system could potentially provide a dramatically different backup experience.

Battery resilience is partly:

Equipment

and partly:

Energy management.

Does Every Battery Support Backup Power?

Do not assume so.

Ask specifically:

“Will this battery provide power when the grid is down?”

Battery installations can be configured for different purposes.

Some systems primarily focus on:

• Solar self-consumption

• Utility-rate optimization

• Demand response

• Grid services

Backup functionality may require additional:

• Transfer equipment

• Gateway equipment

• Controls

• Electrical work

• Load-management equipment

The exact requirements depend on the battery and electrical design.

Do I Need a Battery Just Because I Have Solar?

No.

Battery storage can be extremely useful for some homes.

But that doesn't mean every Illinois solar system should include one.

Potential reasons to add storage include:

Frequent outages

Critical household loads

Medical equipment

Well or sump pumps

Desire for backup power

Increased solar self-consumption

Certain utility-rate strategies

But batteries also add:

Cost

Equipment

Complexity

and:

Warranty considerations.

That's why our approach is:

Identify the problem first.

Then determine whether a battery solves it.

What Does the Centralia Case Study Not Prove?

This is important.

Illinois Shines reports that this particular household:

• Cut monthly electricity bills roughly in half

• Received approximately three hours of backup capacity

• Improved energy reliability

That does not mean another Illinois homeowner should expect the same outcome.

Different households have:

• Different electricity rates

• Different utilities

• Different consumption

• Different solar systems

• Different batteries

• Different financing

• Different incentives

• Different backup loads

• Different weather

The case study is useful because it demonstrates what is possible.

It is not a universal savings or backup guarantee.

What About Illinois Battery Incentives?

Battery incentives should be separated from Illinois Shines itself.

Illinois Shines provides incentives through the purchase of Renewable Energy Credits associated with qualifying solar projects.

Battery rebates available to qualifying Ameren Illinois and ComEd customers are separate utility programs. Illinois Shines' current consumer materials confirm that utility storage incentives are distinct from the Illinois Shines REC incentive.

Current Illinois Shines Disclosure Form guidance also warns that storage systems receiving certain utility rebates may be required to participate in utility programs involving scheduled battery discharge windows.

So before accepting a battery rebate, ask:

What do I receive?

Who receives it?

What program obligations come with it?

Can the utility discharge the battery during certain windows?

How does that interact with my backup reserve?

Never evaluate an incentive without evaluating its conditions.

What About Springfield and CWLP?

Springfield homeowners are served by:

City Water, Light and Power — CWLP

not Ameren Illinois for municipal electric service.

That means you should not automatically assume an Ameren or ComEd battery rebate applies to a Springfield property.

CWLP has its own:

• Solar rules

• Interconnection process

• Net-metering program

• Rate structure

This distinction is especially important because utility rules can materially change battery economics.

Our Ameren vs. ComEd vs. CWLP Solar guide explains why the service utility should be identified before designing the system.

Does a Battery Reduce My Electric Bill?

Maybe.

But backup power and bill savings are two different value propositions.

A battery may help a homeowner:

Use more solar electricity later

rather than exporting it immediately.

That can be financially useful under some utility structures.

But the battery itself has a cost.

So the correct comparison isn't:

Battery saves electricity = battery automatically saves money.

It should be:

Solar-only cost and savings

versus:

Solar + battery cost and savings

plus:

The value you personally place on backup power.

For some homeowners, outage protection is the primary reason for storage.

That's okay.

Not every benefit needs to be expressed as a payback period.

Could a Generator Be Better?

For some households, possibly.

A battery isn't the only form of backup power.

Generators can provide:

• High power output

• Extended operation if fuel remains available

• Support for large household loads

But generators also involve considerations such as:

• Fuel

• Noise

• Exhaust

• Maintenance

• Startup

• Fuel storage

• Emissions

Solar + battery has a different advantage:

The sun can potentially recharge the battery.

There isn't one universally correct backup solution.

Some homeowners may even use both.

How Should You Decide What to Back Up?

Create a priority list.

Tier 1 — Must stay on

Examples:

• Medical equipment

• Sump pump

• Well pump

• Refrigerator

• Freezer

• Essential heating equipment

Tier 2 — Strong preference

Examples:

• Internet

• Selected lights

• Television

• Garage door

• Kitchen outlets

Tier 3 — Nice to have

Examples:

• Whole-house AC

• Electric dryer

• Hot tub

• EV charging

• Nonessential appliances

Your list may look completely different.

That's the point.

Battery design should begin with:

Your priorities.

10 Questions to Ask Before Buying a Solar Battery

1. How many usable kWh does the battery provide?

Not just the marketing capacity.

2. What's its continuous power output?

Capacity and power are different.

3. Which circuits will be backed up?

Get an actual list.

4. Is this essential-load or whole-home backup?

Know what you're buying.

5. Can solar recharge the battery during an outage?

Verify the specific system design.

6. Can the system start again if the battery reaches its minimum reserve?

Understand outage recovery behavior.

7. How long should my priority loads last?

Ask for calculations based on your actual loads.

8. What warranty applies?

Years, cycles, capacity retention and labor can matter.

9. Which utility rebate is being assumed?

And what obligations come with it?

10. What happens if my installer goes out of business?

Know the battery manufacturer, monitoring platform, warranties and service process.

Our guide to what happens if a solar company goes out of business in Illinois explains why separating the installer from the manufacturer and other companies matters.

Frequently Asked Questions

Will my solar panels work during a power outage?

A standard grid-connected residential solar system generally shuts down when the utility grid fails. Backup operation normally requires properly configured equipment such as battery storage, compatible inverters and isolation controls.

Does a solar battery automatically power my whole house?

No. Backup capability depends on battery capacity, power output, electrical design and the loads connected to the backup system.

How long will one battery last?

There is no universal runtime. It depends on usable battery energy and how much electricity the protected loads consume.

Can solar panels recharge a battery during an outage?

Potentially, yes, if the solar + storage system is specifically configured to operate while disconnected from the grid.

Will a battery run central air conditioning?

Some systems can, but HVAC can create substantial power demand. Battery output, capacity, startup requirements and the overall electrical design must support the equipment.

Can a battery operate a well pump?

Potentially. Pump power and startup demand need to be included in the system design.

Can a battery power my sump pump?

Potentially, and sump pumps are a common priority during storm-related outages. Verify the pump's electrical requirements.

Will four batteries give me three hours of backup?

Not necessarily. The Centralia Illinois Shines project happened to use four batteries and Illinois Shines reported approximately three hours of backup under that household's system and loads. Another home's runtime could be very different.

Do Illinois Shines incentives pay for batteries?

Illinois Shines primarily provides solar incentives through REC purchases. Qualifying Ameren and ComEd customers may have separate utility battery/storage rebates with their own eligibility and participation requirements.

Does every Illinois home need a solar battery?

No. The value depends on outage risk, critical loads, utility rules, solar production, household consumption, equipment cost and the homeowner's goals.

The Biggest Battery Question Isn't “How Many?”

When homeowners ask:

“How many batteries do I need?”

we're actually missing several questions.

What are we powering?

For how long?

During what kind of outage?

Will solar recharge the batteries?

What happens during cloudy weather?

Which loads can we turn off?

What happens if the outage lasts three days instead of three hours?

Those answers determine the system.

The new Centralia case study is useful because the homeowners didn't add storage simply because batteries were popular.

They had a specific problem:

They needed reliable electricity for essential water and heating systems during recurring outages.

The battery solved a real need.

That's how storage should be evaluated.

Thinking About Solar + Battery Backup?

At LuNova Solar, we believe the battery should have a job.

Maybe that job is:

Keep the sump pump running.

Maintain a well.

Protect medical equipment.

Run essential circuits.

Keep the refrigerator cold.

Increase solar self-consumption.

or:

Provide greater peace of mind during Illinois storms.

Then the system should be designed around that job.

SEE IF SOLAR + STORAGE MAKES SENSE FOR YOUR HOME

No automatic battery upsell.

Just a clearer look at what you actually want your home to do when the grid goes down.

Related Illinois Solar Guides

Solar Battery in Illinois: Do You Need One?

Illinois Net Metering 2026 Guide

Ameren vs. ComEd vs. CWLP Solar

What Happens After You Sign a Solar Contract in Illinois?

Does Solar Work in an Illinois Winter?

I Got a Solar Quote. Now What?

10 Solar Sales Red Flags Illinois Homeowners Should Know

What Happens If Your Solar Company Goes Out of Business in Illinois?

Before You Go Solar in Illinois: 7 Things Every Homeowner Should Check

Sources & References

Illinois Shines — Gragg Street Farm Small Distributed Generation Case Study, September 2026

Illinois Shines — Consumer FAQs

Illinois Shines — Distributed Generation Disclosure Form Storage Guidance

U.S. Department of Energy — Solar and Resilience Basics

U.S. Department of Energy — Homeowner's Guide to Solar

LuNova Solar provides general educational information and does not provide engineering, electrical, financial, tax, legal or emergency-preparedness advice. Battery runtime, backup capability, savings, solar recharge, utility incentives and equipment performance vary significantly by system design, household loads, weather, utility rules and equipment. Backup systems should be designed and installed by qualified professionals.