Battery Load Shedding: How It Keeps Your Home Powered

Battery load shedding means your home battery automatically turns off lower-priority circuits during an outage, so the stored energy goes to what matters most. A battery that would drain in hours while running the whole house can last far longer when it powers only the refrigerator, lights, internet and a few outlets. The shedding can be set by state of charge, by circuit, or by the appliance.

This guide explains how load shedding works in a home solar-plus-battery system, which loads to shed first, how Tesla and Enphase systems handle it, and how to plan it with your installer before the next outage.

TL;DR

• Load shedding disconnects non-essential loads when the grid is down, so limited stored energy is spent on essentials.
• Heavy thermal loads (electric water heating, dryers, ovens, baseboard heat, and often air conditioning) are the usual first cuts.
• Many systems shed in tiers by battery state of charge, dropping lower-priority circuits first as the battery drains.
• Sizing and shedding work together: a bigger battery buys time, and a sensible shedding plan stretches it.
• Your installer should set up the shedding plan when the system is designed, not after the first outage.

Table of Contents

• What battery load shedding means in a home
• Why shedding matters: the runtime math
• What to shed first, and what to keep
• How the battery decides what to shed
• Shedding for generators versus batteries
• Timing matters in San Diego
• Sizing the battery around your shedding plan
• How to build your load shedding plan: 6 steps
• Perspective
• Get a shedding plan built into your system
• Common mistakes to avoid
• FAQ
• Sources

What battery load shedding means in a home

In a grid-tied home with a battery, an outage turns your house into a small island. The battery and your solar panels (if the sun is up) are the only sources. Unlike the grid, that island has a hard limit: the battery holds a finite amount of energy, and it can only deliver a finite amount of power at once.

Load shedding is how you manage both limits. You decide which circuits keep power and which get disconnected, either from the start of the outage or as the battery drains. A simple example: with the battery partly charged, you could cut power to non-essential loads like hallway lights so a freezer stays running. Energy-storage glossaries describe it the same way, as reducing demand on a storage system so critical loads keep power when stored energy is scarce.

Two limits are in play, and it helps to keep them apart:

• Energy (kWh): how much total electricity the battery holds. This decides how many hours you get.
• Power (kW): how much the battery and inverter can deliver at one moment. This decides whether big loads can start at all.

Shedding helps with both. Removing a large load lowers the instant draw, and it also slows how fast the stored energy disappears. If you want a deeper look at matching kWh to kW for your house, see our guide to matching kWh to kW for whole-home backup.

Why shedding matters: the runtime math

Runtime is stored energy divided by your average load. A 13.5 kWh battery running a 1,000 W load lasts roughly 13 hours in theory, and the same battery running 250 W lasts about four times as long. Real systems lose a little to conversion, but the principle holds: cut the load, and you multiply the hours.

The biggest wins come from removing a few large loads, not from switching off lots of small ones. A space heater, an electric dryer or an electric water heater can each draw more than everything else in the house combined. An air conditioner compressor is a heavy draw too, which is why it is the classic candidate for shedding.

Research from Lawrence Berkeley National Laboratory shows why this matters in practice. Its modeling of solar-plus-storage backup found that backup performance generally declines the longer an outage lasts, and is lowest for outages that begin in the early evening in warm months. The reason is timing: when a utility’s time-of-use rates reward battery discharge from 3 to 8 pm, there may be little charge left when the sun has set and an outage hits.

The same brief tested a conservative case, a 10 kWh battery in Maricopa County, Arizona. There, the system only partly met the backup load in 43 to 84 percent of outages, depending on which loads were included. Larger systems or grid charging improved results, but covering heating and cooling still did not reach 100 percent consistently. The lesson for San Diego homeowners is that load selection decides how an outage feels. A battery asked to run central air conditioning and everything else will fall short, and a battery asked to run essentials will go much further.

What to shed first, and what to keep

Sort your home into three tiers. This is the same approach most battery systems use, whether the tiers are called critical, important and non-essential, or something else.

Tier 1: always on

These circuits stay powered until the battery is empty.

• Refrigerator and freezer
• Core lighting
• Internet modem and router, phone charging
• Garage door opener, if it is your only way out
• Medical equipment, if anyone in the home relies on it
• Furnace blower or other low-draw comfort items you consider vital

Tier 2: on while the battery is healthy

These run while there is plenty of charge, then drop off as it falls.

• Home office outlets and TV
• Kitchen outlets for a microwave or coffee maker
• A single air conditioner or mini-split in one room
• Well pump or sump pump, if you have one and need it daily

Tier 3: shed immediately

These are the heavy, continuous thermal loads and the nice-to-haves.

• Electric water heater
• Electric dryer
• Oven and cooktop elements
• Baseboard or resistive electric heat
• Pool pump and spa heater
• EV charger (unless you have deliberately sized for it)

One smart-panel manufacturer describes the same logic with three circuit groups. In its approach, must-have circuits stay on during backup, typically refrigeration and lighting. Nice-to-have circuits are powered only while the battery is at 50 percent or higher, and non-essential circuits are never powered in a backup event. The company says this kind of categorization can extend battery runtime by up to 40 percent, which is a manufacturer’s claim for its own system, so treat it as an illustration of the idea rather than a promise for your home.

How the battery decides what to shed

There are three common ways a system sheds load. Which ones you get depends on the battery brand, the gateway or panel, and how your installer wires the house.

1. Circuit selection at install (the backed-up loads panel)

The simplest form of shedding is deciding which circuits are backed up at all. Your installer moves essential circuits to a separate backup subpanel, and everything else stays on the main panel and goes dark when the grid fails. This is permanent, structural shedding. It costs little extra at install and gives the most reliable result, and it is the first design conversation to have for any battery project.

2. Switched control of a specific big load

Some systems let you wire a control signal to a specific appliance, usually the air conditioner. Tesla’s installation documentation for the Powerwall 2 Backup Gateway describes this: a low-voltage control circuit, rated up to 60 V and 2 A, controls a specific load such as an air-conditioning circuit. When the system is on-grid, the circuit is closed and the load is powered. When the system is running off-grid, the circuit opens and the load is off. The result is that your air conditioner works normally every day and quietly stays out of the way during an outage.

3. Dynamic shedding by battery level

The most flexible approach ties shedding to state of charge. Enphase’s IQ Load Controller is an example. In Battery Mode, homeowners can use the Enphase app to prioritize loads based on how much stored energy remains. Enphase’s own example is keeping the air conditioner running until the battery reaches 30 percent, then dropping it to prioritize more critical functions. You can read how this plays out in a real install in our guide to Enphase load control and the IQ Load Controller.

A tiered plan built on this idea might look like the table below. These thresholds are examples of the logic, not settings for your home, which depend on your battery, loads and priorities.

Shedding for generators versus batteries

People sometimes carry generator habits into battery planning, and the two work differently. A generator is limited by power: starting a large motor load can stall it, so shedding is about avoiding surges. A battery is limited mainly by energy over time, so shedding is about conserving kilowatt-hours. That shifts your thinking from “what can start” to “what is worth the energy.” A lot of modern gear (inverter-driven air conditioners, for example) starts gently, so a battery may handle it fine for a while. The question becomes how many hours of cooling you want to buy with limited storage.

Timing matters in San Diego

San Diego homeowners on a solar-plus-battery setup usually run the battery to avoid expensive SDG&E peak rates. That is good for your bill, and it is exactly the scenario Berkeley Lab flagged: if the battery discharges through the late afternoon, an early-evening outage finds it lower than you would like.

Two practical fixes work together:

1. Set a backup reserve. Most systems let you hold back a share of the battery, for example 20 to 30 percent, that daily bill-saving cycles will not touch. A bigger reserve costs a bit of savings and buys more outage coverage. During fire-season weather, when outages are more likely, many homeowners raise it.
2. Pair a reserve with shedding. A reserve gives you stored energy, and shedding makes it last. A modest reserve with a strict Tier 1 list can carry a home overnight.

Neither depends on guessing the outage. They are settings you can adjust through your battery’s app as the weather or season changes.

Sizing the battery around your shedding plan

There are two ways to approach sizing, and shedding changes the math for both.

Whole-home backup. You want nearly everything to run, so you size for the biggest loads you will keep on and for the hours you need. This takes more batteries and a bigger inverter, and the cost reflects it.

Essential-loads backup. You decide what matters, shed the rest, and size to that list. Often one or two batteries cover a San Diego home’s essentials for a day or more, and the savings versus whole-home sizing can be significant.

Our Battery Storage service is published at $12,000 to $16,000, and the final number depends on how many batteries, which brand and how the home is wired. If you want to see how the numbers play out for your house, our Powerwall sizing guide walks through it. If you are still weighing the investment itself, see whether a solar battery is worth it and the breakdown of home battery payback with incentives.

How to build your load shedding plan: 6 steps

1. List your circuits. Walk the breaker panel and label every circuit with what it feeds.
2. Mark the must-haves. Refrigerator, freezer, lights, internet, medical gear, and anything you cannot live without for 24 hours.
3. Find the big draws. Note the nameplate wattage on the water heater, dryer, oven, air conditioner, pool pump and EV charger. These are your shedding candidates.
4. Decide your comfort line. For example: is cooling worth a few hours of battery, or do you want fans only?
5. Pick the shedding method. Backed-up loads panel, switched control for the air conditioner, or dynamic control by state of charge, based on your equipment.
6. Test it. After install, have your installer walk you through the app and simulate an outage by switching to backup mode, so the first real outage is not the first time you see how it behaves.

Perspective

After 30 years of installing solar in San Diego, the pattern we see is that homeowners buy a battery for the outage and then discover the real decision is which loads to keep. Nobody wants to be surprised at 8 pm when the lights go out and the battery starts to climb down.

Our approach is to design the backup around how the family actually lives. We look at your roof, your energy use and your goals, then decide with you which circuits belong on the protected side. Because our engineering team and our crews are all in-house, the person who designs the shedding plan is part of the same company that installs and services it, and that continuity matters when you want to adjust settings years later.

We also think shedding is the best way to make a battery do more. We install Tesla Powerwall, Enphase IQ and Franklin WH systems, and we plan each one with NEM 3.0 in mind: use your own solar and stored energy first, avoid SDG&E peak rates, and still hold enough in reserve to carry the essentials through an outage. A well-planned shedding strategy is part of getting the most from that investment.

Curtis Williamson

Get a shedding plan built into your system

If you are adding a battery, the best time to decide what gets shed is during design. San Diego Solar designs, engineers, permits and installs battery systems with our own crews across San Diego County, and we handle the SDG&E interconnection paperwork too. Every system is custom designed around your roof, your usage and your goals.

See our Battery Storage page for the options we install, or contact us for a free consultation and a written project timeline before you commit. If you already have solar and want to add storage, we can show you how the circuits would be split. If you already have a battery and it is not behaving the way you expected, our repair and service team can review the setup.

Common mistakes to avoid

• Backing up everything by default. It sounds safe, but it drains the battery quickly and may force an oversized system.
• Forgetting the always-on phantom loads. Routers, hubs, and old second refrigerators add up over a long outage.
• Leaving the reserve at the minimum during fire season. Raise it when outages are more likely.
• Never testing backup mode. Settings that look right in the app can still surprise you under a real load.
• Putting the EV charger on the protected side without planning. A car charging at home can take more than the battery can give.
• Ignoring battery longevity. Battery life depends on chemistry, temperature and how it is cycled; our guide on solar battery lifespan covers what to expect.

FAQ

What does load shedding mean for a home battery?

It means disconnecting lower-priority circuits so the battery’s limited stored energy goes to essentials such as the refrigerator, lights and internet. It can be set at install by choosing which circuits are backed up, or controlled dynamically by battery level. The result is longer runtime during an outage.

Is this the same as the load shedding utilities do?

No. Utility load shedding is the grid operator cutting power to areas when supply cannot meet demand. Battery load shedding is something you control inside your own home, deciding which circuits your battery powers when the grid is down. The words are the same, but the purpose and control are different.

Which appliances should I shed first?

Start with continuous heavy thermal loads: electric water heating, clothes dryers, oven elements and electric baseboard heat. Air conditioning, pool pumps and EV chargers are next on most lists. Keep refrigeration, lighting, internet and any medical equipment on the protected side.

Can I change my shedding settings later?

Often yes, depending on the system. Systems with app-based controls let you change priorities and reserve levels yourself. Structural changes, such as moving a circuit to or from the backup panel, need an electrician or your installer. Ask your installer which settings you can change yourself.

Does shedding make the battery last longer overall?

It makes a single outage last longer by lowering your average draw. How long the battery lasts over years depends on chemistry, temperature and cycling, which we cover in our solar battery lifespan guide.

Sources

• Backup Power Performance of Solar-plus-Storage, Lawrence Berkeley National Laboratory
• Load Shedding, Tesla Powerwall 2 Backup Gateway install manual
• What is IQ Load Controller, Enphase
• Backup Overload Protection, SPAN blog

Recommended

• Home Battery Safety: What San Diego Homeowners Should Know
• Is a Solar Battery Worth It?
• Enphase Load Control: How the IQ Load Controller Works
• How to Get Powerwall Sizing Right for Your Home