continuous vs startup power

What is the difference between continuous and startup power?

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As you compare options for energy storage systems, there are a few key technical specifications to focus on and questions to answer. How much energy can the battery store? How much of your home can the battery power, and for how long? Can the battery keep powering some or all of your home if the grid is down? And can your battery provide a momentary burst of power large enough to start up your largest appliances, like your air conditioner? 

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Answering that last question is where the difference between continuous and startup power come into play. Let’s jump right in. But first, some quick energy storage 101 refreshers. If you’re already familiar with the difference between power and usable energy capacity, and already know why the power rating is important, feel free to skip ahead.  

A quick refresher on energy storage terminology

Energy storage systems have both a power rating, expressed in kilowatts (kW), as well as a usable energy capacity rating, expressed in kilowatt-hours (kWh). One useful analogy you can use is to think of your battery like water running through a pipe: the usable energy capacity is the amount of water available to push through the pipe, while power is the size of the pipe itself. 

Larger pipes allow more water to flow through at once, which depletes the water faster. Similarly, a battery with a high power rating can deliver more electricity at one time, but will burn through its available energy capacity faster too if you use it at its maximum power rating.

What is a battery’s power rating important?

A battery’s power determines which, and how many, appliances you can run from the battery all at the same time. The most popular batteries today have a standard power rating of 5 kW: this is the same for both the LG Chem RESU 10H and the Tesla Powerwall 2, two of the most installed batteries in homes in the US. As a result, a power rating below 5 kW can reasonably be considered small, and a power rating above 5 kW can be considered above average. 

When considering which battery is right for your home and usage patterns, it’s useful to take a look at the power draw from the appliances you plan to run with your backup battery. For instance, a clothes dryer can consume upwards of 4 kW for the duration of the load of laundry you’re drying. Your refrigerator, on the other hand, only uses around 200 Watts. Knowing what you want to power, and for how long, is the best way to size your storage system. 

Importantly, it’s worth noting that some batteries can be stacked together to increase their power output, while others only increase the amount of energy you can store. For instance, adding a second LG Chem RESU 10H in a standard configuration doesn’t necessarily mean that now you have 10 kW of power; rather, you’d need an additional, separate inverter in order to increase the capacity output of the system as a whole. With other batteries, however, the power output scales as you install additional batteries: for instance, a system with two Encharge 10s would give you 7.68 kW of power.

The difference between peak and continuous power

Not all types of power supply are created equal, nor are all types of power demand created equal. In your home, you have appliances and devices that require a constant amount of power to operate whenever they’re plugged in or turned on, such as your refrigerator or wifi modem. Other appliances, however, require a surge of startup power to even turn on, before running at a more constant power demand from then on, such as an HVAC system or a sump pump. 

This is where the difference between peak and continuous power comes into play: peak power is the amount of power that a battery can push out over a very short period of time to allow you to turn on some of those more power-hungry appliances. If you live in a place that experiences the loss of power at the same time as flooding–for instance, in a hurricane-prone area–having the backup power to get your sump pump back up and running is essential. Additionally, if you plan to be able to run your HVAC unit off of your energy storage system, you’ll need to have enough peak power output to cover the surge associated with turning on your AC.

After the initial surge, most of these power hungry loads and appliances return to a level of power demand that easily falls within the bounds of a battery’s continuous power. But do keep in mind that running your HVAC or dryer will deplete your stored energy faster than just keeping your lights, WiFi and TV on. 

Comparing the peak and continuous power of popular batteries

Here’s a comparison of the peak and continuous power ratings for some of the most popular batteries quoted on EnergySage. To learn more about each of these batteries and more, visit the EnergySage Solar Battery Buyer’s Guide.

Peak/continuous power for popular batteries

BrandModelPeak power (kW)Continuous power (kW)
TeslaPowerwall 27 (10 sec)5
LG ChemRESU 10H7 (10 sec)5
EnphaseEncharge 105.7 (10 sec)3.84
PanasonicEVAC-105-Plus9.6 (5 sec)5.5
sonneneco 1012 (5 sec)8
EguanaEvolve-268.5 (5 sec)5
GeneracPWRcell M612 (2 min)6.7
Electriq PowerPowerPod 17.17.5 (1 sec)5.5
Blue Planet EnergyBlue Ion 2.017 (1 sec)8

Explore your storage options today

EnergySage lets you compare quotes from multiple different installers in your area for free, all from the comfort of your home. With so many different battery options available today, it’s easy to work with installers to find the system that fits your needs. And if you have any questions about your solar or storage offers on EnergySage, our team of Energy Advisors are here to help with unbiased answers to all of your questions. To get started, register for an account on the EnergySage Marketplace today!

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About Spencer Fields

Spencer is the Manager of Market Strategy & Intelligence at EnergySage, where he writes about all things energy. Prior to joining EnergySage, he spent five years at Synapse Energy Economics, providing environmental, economic and policy analysis for public interest groups. Spencer has degrees in Environmental Studies and Hispanic Studies from Brown University, meaning when he's not in the office you can find him outside or traveling somewhere to work on his Spanish.

2 thoughts on “What is the difference between continuous and startup power?

  1. Kim Peterson

    I want to have an emergency electrical system that will provide power for the basics in my home during an emergency and potentially for an extended period of time if the Grid is down.
    I want to combine solar panels, battery storage and a gas powered generator.
    So I’d like to run the house off of the solar panels or the gas generator or the storage battery.
    I’d like to be able to recharge the storage battery with solar panels or the gas powered generator.
    So what are the tranistion system / switching components that I would need to set this up?

    1. Scott Cepek

      This is what I have done: The solar keeps the batteries topped off while the grid is up. When there is an outage, I have a transfer switch (Interlock) that I can flip in the fuse box to allow a 220 plug to go from the fuse box input to either the battery power or the generator for the whole house. An 8,000-10,000 watt genni should power most needs, though I found that just running the water heater and minor appliances first and turning up the water heater temp for the first 30-45 minutes (electric water heater), then turning the breaker off for the water heater allows me to have hot water (hotter than normal during outages so it goes farther), and running everything else without the WH pig taking up all the juice. I also chose to buy a used diesel genni vs a new gas one. The diesel should last longer, and the fuel stores MUCH longer. The 10 year old genni I bought still has the same fuel from 10 years ago, no issues. Storing diesel in 55 gallon barrels is safer than gas, & adding stabilizer to it means I don’t worry about fuel for years. The type of battery you choose is important, look at how fast it can recharge. Slower charging means more fuel usage. You want to only need the genni for 5-10 hours every day or 2, and rely on battery power when all your large power needs have been met during genni running.


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