How Much Battery Backup Do I Need For My House?

You’ve decided to prepare your home with battery backup power. A wise choice. "But", you wonder, "how much solar battery storage do I need?"

A customer of ours was in the same situation recently. He was relying on a small backup generator for power outages. After moving, he knew he needed a better system to handle the increased electricity needs of his new home. And so the research started. 

How would you go about it? Predicting how much battery backup you need for future emergencies can be confusing. You don't want your whole house to shut down if caught without power. And you don’t want to run out of battery backup because the system you've chosen isn't big enough for your needs. 

Who wants to live without power in an emergency? If you do, there is no need to keep reading. But for the rest of us who understand the responsibilities that come with owning a home, here are the steps to calculate how many batteries to power a home based on the amount of electricity you use:

Quick Links

How to Size a Battery Backup
What Size Solar Battery Do I Need?
How Many Solar Batteries Do I Need?
How to Charge a Backup Battery at Home
Alternatives to Battery Backup

BONUS

How to Save Money on Your Electric Bill with a Backup Battery

How to Size a Battery Backup

1. Identify essential appliances

Not all appliances in your house need to run during an emergency. That's why a good place to start is to make a list of the watt hours for the ones you want to keep running. Our customer who started researching a new system knew he needed electricity for his fridge, freezer, microwave, TV, lights, heat pump, and furnace.

After you create a list of appliances, add the wattage of each appliance together. This will help you determine the amount of energy you need to keep your house running the way you want it.

Here's a list of common home appliances and how many Wh they consume on average:

2. Decide how long you need backup power.

The frequency of blackouts and power outages in the United States has been on the rise in recent years. And the time to restore power is getting longer.

Small incidents can be fixed quickly. But big disasters and bad weather can cause outages that last for hours, days, or even weeks.

Our customer decided he needed to protect his home for up to 7 days without power, but your needs might vary. One way to estimate this is to look up the average length of power outages in your county.

Once you know the details of your energy usage and how many hours per day you'll need power, you can understand how many solar batteries are needed to power a house.

What Size Solar Battery Do I Need?

Here's a formula to find out what size solar battery you need: Take the total kilowatt hours kWh that your essential appliances use and multiply it by how long you want the backup power to last. (kWh you use per day x how many days you need backup power = battery size that can support your home)

For example, during power outages and blackouts, the average Midwest American home uses about 8 kWh of electricity per day (if they're prepared with a backup power station).

So in the case of the customer who wanted backup power for 7 days, he needs:
8 kWh per day x 7 days = 56 kWh

Now we've found that to keep his house running for up to 7 days, he needs a solar battery capacity that is at least a 56 kWh.

How Many Solar Batteries Do I Need?

Now that you know how many kWh it takes to back up your home, you can figure out how many batteries it takes to achieve that capacity. For some people, one battery with a large capacity might be enough. But if your home has a high energy demand, chances are you will need more than one backup battery.

Before you calculate how many you need, you want to find a solar battery that's everyday reliable, easy to install, and that you can trust in an emergency.

With these things in mind, a brand called EcoFlow stands out as a good solution. EcoFlow is reliable because they use LiFePO4 batteries instead of lithium ion batteries. The battery type is important because the LiFePO4 type of batteries last 10 times longer than lead acid batteries and are considered much safer than lithium ion batteries.

There are two EcoFlow products that can serve as complete home backups. The EcoFlow Delta Pro and the new Delta Pro ULTRA.

EcoFlow Delta Pro

The EcoFlow Delta Pro was the standard in long-term power storage and home backup before the ULTRA came out. The Delta Pro has an expandable capacity from 7.2 to 21.6 kWh (when you add the extra batteries). You need two Delta Pros, a Double Voltage Hub, and four extra batteries to unlock the full 21.6 kWh capacity. This is enough capacity to keep your essential appliances like fridges and freezers running for up to a week.

Installation for this setup is easy if you have a generator inlet. You can plug the Double Voltage hub straight into the inlet and plug the Delta Pros into the hub. Easy.

If you do not have a generator inlet, a certified electrician can install one for you. This usually costs about $1,000. (Contact us to find out how Lakehouse & Cottage can support you with White Glove installation services and special offers).

The cost for this setup, which includes 2 Delta Pros, the Double Voltage Hub, and 4 extra batteries is $13,995.

For most people, this bundle is the answer to "how many batteries to power a house through an emergency?" But if you have a greater electricity usage (like our confused customer), you will need to step up to a more capable option. The EcoFlow Delta Pro ULTRA. 

EcoFlow Delta Pro ULTRA

A more robust option is to use the newer EcoFlow Delta Pro ULTRA. The ULTRA makes it easy to start small and expand later. 

Just one Delta Pro ULTRA inverter and one battery have a 6 kWh capacity and 7.2 kW output. This has you covered for minor blackouts and outages.

Of course, our customer needed something with 56 kWh capacity to handle his high-demand electric appliances for a full week. We suggested the minimum he should start with would be one Delta Pro ULTRA inverter and five batteries. This setup has a 30 kWh capacity and 7.2 kW output. 

There are three options to install the EcoFlow Delta Pro ULTRA:

1. If your home has a generator power inlet, you can simply plug the Delta Pro ULTRA straight into that.
2. You can get the EcoFlow Smart Home Panel 2, which gives you the option to expand to more ULTRA units later on. The Smart Home Panel 2 requires professional installation. This costs around $3500. (Ask us about Lakehouse & Cottage's white glove installation services and special offers).
3. You can install the EcoFlow Delta Pro ULTRA Transfer Switch A510A - 125/250v with 50amp. Professional certified electrician installation for the transfer switch is usually about $2500. (Ask us about Lakehouse & Cottage's white glove installation services and special offers).

One ULTRA inverter, 5 batteries, and the Smart Home Panel 2 cost $19,495 (Does not include installation).

For high-demand electric appliances and total home backup, the Delta Pro ULTRA is the safer bet to go with over the Delta Pro. That's not an exaggeration either. We gathered feedback, reviews, and real world simulations of the Delta Pro ULTRA so that you can judge for yourself.

In the case of the customer with a high home electricity demand, the best bundle of how many batteries to run a house for up to 7 days is..

Two Delta Pro ULTRA Inverters and Ten Batteries.

This is the best solution for our his needs based on how much electricity his house consumes. Each ULTRA battery provides an extra 6 kWh of energy storage and 7.2 kWh of output.

It's the most precise setup that reaches the 56 kWh benchmark he was aiming for. It finally answers the question: "How much battery storage do I need?".

Ten ULTRA batteries can run your home's highest-demand appliances like the heat pump, furnace, refrigerator, freezer, bedroom and bathroom lights, computer, TV, etc. Since it involves 2 inverters, you also need the Smart Home Panel 2.

The cost for this entire setup would be $37,494 (plus the professional installation for the Smart Home Panel 2 is about $3500).

Maximum Peace of Mind with Maximum Capacity

Or really take your home power storage to the top level with up to 90kWh battery capacity. For a standard household, that's over 30 days of essential backup power. The Delta Pro ULTRA lets you connect and stack up to 15 batteries when plugged into the Smart Home Panel 2.

This bundle effortlessly runs ALL energy-hungry household items, like a 3-ton central air conditioner, your heat pump, furnace, and more for up to a month. This complete setup costs $55,493 (plus the professional installation for the Smart Home Panel 2 about $3500).

How to Charge a Backup Battery at Home

Recharging a solar generator or backup battery at home is easy. Recharge at home with three convenient methods so you are always prepared with backup power:

1. Recharge with Wall AC

Plug your backup battery into a standard wall outlet for a quick and reliable charge.

Plus, with the Smart Home Panel 2, you can set up recharging to work with Time-of-Use rates. This means your unit will charge when the price of electricity is low and you can use that stored energy to power your house when rates are high.

2. Recharge with Solar

Take advantage of the sun's energy by using a solar panel system to recharge your backup battery. Using solar panels and battery power together is an eco-friendly option that provides an independent and renewable power source.

The EcoFlow Delta Pro ULTRA allows connection with both high and low solar PV ports to get you a high 5.6kW-16.8kW solar input. This means just one hour of solar charging gets you a full day of power for your house. If you use solar to recharge your batteries then the answer to "How many batteries do I need for my solar system?" might be less than if you only rely on AC charging.

3. Recharge with a Generator

In emergencies where other methods might not be possible, a generator offers a reliable backup to charge your battery. 

With the EcoFlow Dual-Fuel Smart Generator, you can choose a specific battery level, and let the Smart Generator turn on and off automatically to charge your Delta Pro or ULTRA. 

Alternatives to Battery Backup

If you've discovered that your house needs an extra large capacity and solar batteries no longer make sense to you, there are a few alternatives to battery backup that are worth considering. Standby home generators and portable gas generators can be reliable options.

Standby home generators are hooked up to your home's existing fuel supply and automatically turn on during a power outage. Though this is a hassle-free solution, they can require large installation costs.

A portable gas generator is often more cost effective, at least initially. But they can end up needing more maintenance in the long run and you will have to store gas to fuel them which can degrade quickly (3-6 months). Unless you get one like this that has dual fuel capabilites and can also run on propane (LPG). Propane has a much longer shelf life than gasoline which makes it easier to store to prepare for an emergency.

-------------------------- BONUS ----------------------

How to Save Money on Your Electric Bill with Backup Battery

Saving money on your energy bills with a backup battery is a smart move. With a backup battery, you can charge the battery when energy is cheap, then use it during peak hours to save money and avoid high rates. The EcoFlow systems are great because they automatically take advantage of these Time-of-Use rates.

You can also get a 30% Solar Tax Credit when you install the EcoFlow Delta Pro ULTRA for even more savings.

Not to mention how expensive and stressful losing power for an extended amount of time can be. Bursting frozen pipes, flooded basements, rotting food... These costs can be avoided if you have a whole-home backup battery. In fact, the savings that from avoiding a single outage can more than make back your investment with the Delta Pro ULTRA.

Shop the EcoFlow Delta Pro ULTRA now.
Don't forget to reach out to Lakehouse & Cottage for help with installation or special offers.

Still have questions?

We'd be glad to tell you anything more you want to know. Just drop us a line at sales@lakehouseandcottage.com or call us at 854-777-0909 Mon-Fri 9a-5p CST with all your EcoFlow Delta Pro Ultra and home backup questions.