How to Choose the Correct Sized Power Backup System: A Complete Guide
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When it comes to protecting your home from power outages or extending power to off-grid areas, a power backup system or solar generator is an essential investment. Whether you're looking to keep your lights on during a storm, preserve the contents of your refrigerator, or ensure that critical medical equipment stays running, having a properly sized backup system is crucial.The right backup system offers reliability and peace of mind during unexpected blackouts, while the wrong one can lead to frustration and pain when you realize it’s not going to keep the freezer running when you were counting on it to. But how do you determine the right size for your home power backup system?
This guide will walk you through the process of sizing your backup system correctly, helping you choose the right solution for your home’s energy needs.
Understanding Your Power Needs
Before selecting a backup power system, the first step is to understand how much power you actually need. This involves identifying the appliances and devices that you want to keep powered and calculating their total energy consumption. We’ll focus on home systems for the purposes of this article, but the same things apply to smaller mobile systems.
Identify Essential Appliances and Devices
To determine your energy needs, you’ll start by listing the essential appliances you want to power during an outage or off-grid. These are critical devices like:
- Refrigerator or freezer
- Medical equipment (such as oxygen concentrators or CPAP machines)
- Lights (for basic illumination)
- Cell phones or other critical communication devices
- Sump pumps (to prevent flooding)
In addition to essential loads, consider non-essential but desirable items, like:
- TVs and entertainment systems
- Computers or home office equipment
- Air conditioning or heating systems (although this tends to really drive up costs and sizing needs due the massive power draw of HVAC)
Determine Your Power Consumption
Once you've identified which devices you need to power, it’s important to know their energy requirements. Appliances usually have a wattage rating that tells you how much power they use. You can often find this information on the appliance label.
Key measurements for power are:
- Wattage (W): The rate at which an appliance consumes energy.
- Watt-Hours (Wh): The amount of energy consumed over time (e.g., if a 100-watt appliance runs for 10 hours, it consumes 1,000 watt-hours). Batteries will generally give their size in watt-hours.
For example:
- A refrigerator might use about 100-800 watts depending on its size and efficiency.
- LED lights use approximately 10 watts each.
- A laptop might consume 50-100 watts when charging.
To calculate how much power you'll need, simply add up the wattage of all the devices you want to run at the same time, and consider how long you’ll need to power them.
One important thing to consider here is that some devices, like a refrigerator, will give you their running wattage rating, but won’t use that power the whole time they’re plugged in. A refrigerator, for example, will typically only run about 30% of the time, meaning that the running power consumption in watt-hours will only be 30% of the full wattage draw.
Types of Home Power Backup Systems
There are a few core types of complete systems that you should be thinking about when considering sizing your backup power system as well. The type of system that you choose will heavily influence how you need to think about sizing your system. For example, if you want to run your whole home on a power station + gas generator combo, you may want to get a station with high output capacity, but be less concerned about the total Wh battery capacity, as you can simply store fuel for the generator rather than a bunch of batteries.
1. Backup Battery-Only Systems
These systems rely on battery storage only and can be used for short-term outages, typically in small to medium-sized homes. These systems are ideal for powering critical devices like lights, phones, and refrigerators during short-term power outages. While they can be great for very short-term needs, it tends to be very easy to use up their capacity quickly, especially if you’re powering energy-hungry whole-home systems, so they can require really scaling up battery size, which increases expense greatly. If you want a whole-home system that can store enough power for your entire house for 24 hrs, that’s typically going to require 10-30kWh, and will cost about $7,000-$20,000.
Fortunately, as you’ll read below, there are a few other options that can be easily paired with a power station to constantly generate power while off-grid.
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2. Backup Systems with Generators
Generators (gasoline, propane, or natural gas-powered) are popular choices for homes that need to power a variety of appliances for longer durations. A gas-powered generator can keep your home running during an outage, providing the flexibility to power everything from lights to large appliances.
When you pair it with a power station/battery, using the generator to charge the power station, which powers your house, it can work extremely well. This setup allows you to store a far greater amount of power far more cheaply than batteries. 20kWh of propane can be stored in a 5 gallon tank that costs $50, and $15 to refill. 20kWh of battery capacity will run you $10,000-$15,000.
One of the larger cons to a generator is the necessity of constantly turning it off and on again. Worth noting, there is currently one product on the market, the EcoFlow Smart Generator 4000, that takes care of this issue with a smart start-stop feature. When paired with an Ecoflow Delta Pro line power station, the generator will kick on when the battery hits a minimum threshold, and run until the battery is full, then shut off again, giving you maximum efficiency.
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3. Solar Generator Systems
A solar generator system adds in solar panels as the charge mechanism for the power station. The great thing about solar panels is that after the initial up-front cost, charging is free, and always available as long as the sun comes out. The big downside is that for half the day, the sun isn’t charging your panels, and depending on the size of your solar array, your power station may not fully charge if conditions aren’t right, with a full sun day. In short, you’re locked into the amount of power that you can produce and use in a day's time in a way that you’re not as much with a traditional gas or propane generator.
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Step-by-Step Guide to Sizing Your Backup System
1. List All Loads
Identify and prioritize appliances that you’re looking to power. You may want to consider splitting the list into critical loads, such as refrigerators, medical devices, etc., and auxiliary loads that are not as necessary, but would be nice to power, such as TV’s, computers, etc. Once you’ve written each of them down, find the wattage draw for each, both running and maximum, and list those as well.
2. Calculate Total Wattage
Add up the wattage of each critical load, factoring in both running wattage and peak wattage. This will give you the total wattage your backup system needs to handle. Consider the fact that you may not need to power everything at once. For example, you may want to power a coffee pot, but you may not ever need to run that at the same time as the washing machine. A fridge, on the other hand, is going to run constantly, so should definitely be added in fully. You’ll want to make sure that your maximum wattage draw at any given time does not exceed about 80% of what your system is rated for, ideally.
3. Consider Battery Runtime Needs
Before beginning, consider how long you need your system to be able to power you for. Are you looking for something that can power your devices for multiple days, or just a few hours while power is out? This will obviously heavily affect how much you intend to use each device listed.
Determine how long you need the backup system to run each device, then calculate how much battery storage is required to meet that runtime, using the running wattage rating you wrote down and an estimate of how much time you’ll want to use it.
This is based on the simple calculation of running wattage x hours. If you want to run a coffee maker once, it might run at 100W for half an hour, so the total Wh needed for that would be 100W x 0.5h = 50Wh.
Once you’ve calculated everything individually, add it all together, and you have approximately the power station size in Wh that you’ll need. Be sure to leave at least 20% margin for inefficiency, auxiliary needs, and battery degradation over time. If you want to play it safe, more like 50% is ideal.
The one caveat is that if you’re using a gas generator with your power station, you’ll want to just consider fuel quantities rather than battery power. Output varies by generator, but most will give an efficiency rating expressed in a number of Watt-hours per amount of fuel.
4. Choose the Right Generator or Battery Storage System
Once you’ve determined your total wattage and runtime needs, choose a backup system that meets those requirements. Whether you’re looking at a portable power system, a solar-powered system, or a hybrid gas generator option, make sure it can handle your energy demands.
Common Mistakes to Avoid When Sizing Your Backup System
1. Underestimating Power Needs
It’s important to account for all appliances you plan to power. Failing to do so could lead to choosing a system that doesn’t have enough capacity.
2. Overestimating Runtime
Misjudging how long your system can run based on battery or fuel capacity is a common mistake. Always factor in extra time for unexpected conditions.
3. Neglecting Future Power Needs
As your energy usage increases, it’s important to plan for future power needs. Consider any future upgrades or additional devices that may require more power.
Conclusion
Choosing the correct size for your home power backup system is crucial for ensuring reliable performance during power outages. By understanding your power needs, considering all relevant factors, and selecting a system that fits your requirements, you can ensure that your home remains powered when you need it most.
If you’re unsure of what system is right for your home, consult a professional for personalized advice and installation.
FAQ’s
How do I calculate how much power I need for my backup system?
Calculate the wattage of all essential appliances and add up their total running wattage. Consider peak wattage for devices that require extra power to start.
Can a solar backup system power my entire house?
It depends on the size of your solar system and battery storage. Obviously, you need to choose one that’s large enough for your specific needs. That said, an off-the-shelf system like the Ecoflow Delta Pro Ultra is stackable and generally going to be able to handle all but the largest homes.
How long will a gas-powered generator run on a full tank?
The runtime depends on the generator’s size and the fuel tank capacity. A typical home generator might run 8-10 hours on a full tank of gasoline or propane. You can also opt for a more efficient, on-demand generator paired with your power station, like the Ecoflow Smart Generator 4000 with the Delta Pro 3.
What is the most secure backup system?
Nothing beats the power security of a battery backup system paired with a gas generator. With the simplicity and cheapness of storing large quantities of fuel as opposed to batteries, and no need to rely on the sun coming out, or not being able to generate at night, it’s difficult to beat.
Yes, many backup systems (especially solar) can be scaled up with additional batteries or solar panels to meet growing power needs, so you can start with a smaller system today, and add capacity later. Just be sure to get one that offers the ability to scale up to what you will need.