[Battery Series] Batteries vs. Generators
The conversation for our solar customers often includes questions about how to back up your home during a power outage. No one wants to be powerless during a storm or other emergency and thankfully there are several directions you can go. When trying to decide what option is best for you, you will want to think about what you want to back up in the event of a power outage and for how long you want the backup to last. Then you can compare this to your budget. Check out our overview on backup systems here. The more you want to back up and the longer you want to back it up generally works out to be a larger generator or battery system.
The two best ways to add energy resilience to your home, ie not be stuck without power, is either batteries, a generator or both!
There are a few key pros and cons to each:
Whole House Backup or Critical Loads
- Pros: No noise, no exhaust, no maintenance, automatic start, modularity (small to whole home), adaptability, tax credit, a phone app to monitor charge, uninterrupted power supply
- Cons: space requirement, cost depending on size
Batteries come in set sizes that can be stacked to accommodate the end user’s backup goals (total kWh, amperage, instantaneous output and more). For example, Enphase Storage battery comes in 3.5 kWh modules and can be stacked for up to 40 kWh. This gives the homeowner the ability to properly size a system for their needs without overpaying. It also allows them to add more battery power at a later time if needed. All the modern Lithium (Ion and Iron) batteries do not require any maintenance and can be installed with a solar system, which when charged by solar qualify for the 26% federal tax credit.
Battery back-up is preferred by customers who want convenience and performance while minimizing their need to perform maintenance. There is no loss of power in the switch over from grid power to battery power. They do not burn any fossil fuels, there are no exhaust fumes, and best of all they don’t make any noise. The batteries come with a phone app so the state of charge can always be monitored in the palm of your hand. The app also allows homeowners to control the programming of the battery and they can easily toggle from full backup mode to self-consumption, which means the battery is used to maximize the home’s independence from the grid.
A large battery system does require design foresight, as a large battery system can take up a fair amount of space. They can be installed inside or outside as long as it not on a south-facing exposure. An interior garage wall is usually the preferred location. Our team of experts can help with this step.
The first thing we need to distinguish is the differences between a manual start generator and an automatic start generator. Both options have the pros and cons as well.
Manual Start Generator
- Pros: low cost, basic backup power
- Cons: maintenance, theft, exhaust, noise, manual start
The Manual Start Generator tends to be the least expensive option of all the backups. The most common and readily available generator comes as a 30amp pull-start generator and can be found at any home improvement store or your local Costco for between $1000 to $3000 off the shelf. Your electric panel can be retrofitted to add a manual transfer switch (MTS) and generator outlet. When the power goes out you will need to flip the switch in the panel, wheel your generator outside, plug it in, and start it up like a lawnmower. This option will power most of the smaller loads in the home.
The downside is making sure the gasoline in the engine is always good. You may also have to top it off with gas periodically while the power is out during a storm. The most important thing to remember is to always run the generator outside, never inside. It gives off carbon monoxide and can be fatal.
Automatic Start Generator
- Pros: whole home back up, automatic start
- Cons: maintenance, noise, exhaust, possible gas line upgrade, cost
This option comes in multiple sizes and can back up the whole home assuming that is what the homeowner wants. This option is much more expensive than a manual start generator. Whole house generators ranging from 12 kW to 20 kW will be in the ballpark of $9,000 to $13,000 fully installed. When the power goes out, the Automatic Transfer Switch (ATS) will sense the loss of power and start the generator. The homeowner never has to go outside. There will be a momentary loss of power while the generator switches over.
From a design standpoint, there are set back codes from the house to ensure proper ventilation of exhaust. This option requires the generator to be hooked up to the home natural gas or propane line. If it is hooked up to propane, it is recommended to always keep the tank as close to full as possible all times because it uses about 2.5gal/hr. If it is being hooked into an existing natural gas line, then the meter and gas line may have to be upsized to accommodate the extra usage of the generator. This is another added cost to the installation.
Both manual start and automatic generator options need routine maintenance, burn fossil fuels, and create noise (66 decibles). If noise, maintenance, and exhaust are a factor in the decision-making process then a battery might be your best option. When you talk to your Solar Design Consultant, they can help you determine how many batteries or what size generator is required to meet your goals.
Kevin is a Board Certified NABCEP PV Installation Professional and Licensed WA journeyman electrician. He is currently the Sales Manager at Solterra. He is passionate about the outdoors and environmental health, which led him into the solar industry. Skiing and fishing were his main activities before having kids, which now dominate his free time. Through his work at Solterra, he hopes to help do his part so that his kids can continue to grow up in a world with clean air and water.