Keeping the Power On: Batteries v. Generators

batteries vs. generatorsAs power is becoming less of a certainty in our homes, I am frequently asked to provide a quote for a generator or a battery.  Whole house backup with a generator or a battery provides peace of mind and comfort when the power is down.  There is a lot of confusion about the benefits of each.  But, as I have continued to learn through classes, research, and installing both, the answer is clear:  Battery.

There are significant benefits to whole house power backup through battery storage that generators can not provide.

Surprisingly, the long term cost of the battery is significantly less than the generator when operational costs are included in the calculation.

For the purpose of this comparison, we are discussing the Tesla Powerwall specifically, as it has features that other batteries do not.

Please review the following table addressing a few issues:

 GeneratorTesla Powerwall
Whole house or partial house backup
Environmentally friendlyX
Solar production during blackoutX
Utility rebates availableX✔*
Tax credits availableX✔**
Power load shiftingX
Small footprintX
SAves monthly utility expensesX
$0 fuel expensesX
Approx. cost over 10 years$12k-$20k***$4k-$20k***

*SGIP rebate available to PG&E customers but may deplete and refill.  May not be guaranteed.

**24% credit available.  Consult your tax preparer.  May not be guaranteed.

***After credits and rebates, assuming 72 hours of operation per year with LP fuel.

Cost:  Let’s address the issue that most of us are concerned about:  money.  The battery saves money over the generator in three ways.

First, it allows your solar to continue to operate during a blackout, meaning you don’t have to pay for fuel.  If you are using LP fuel, the cost can be $3 per gallon or more.  A whole house generator can use as much as four gallons per hour, meaning a cost of $288 per 24-hour period.  With the Tesla Powerwall, however, your solar will continue to produce power for your home and recharge your battery at no cost to you.

Second, a battery will allow you to use the electricity you generate in a more effective way.  Normally, when you produce your solar energy, you sell electricity to the utility at a low rate and purchase electricity back at a high rate.  With the battery, you charge your battery and use the stored power at times when you would otherwise purchase from the utility.  For example, generate electricity and fill your battery during the day, and charge your car at night.  In addition, stored energy in your battery is automatically used during peak times when it is most expensive to purchase from the utility.  This can create additional savings.

Third, the battery qualifies for rebates and tax credits.  The SGIP rebate, which has a limited funding, but does get refunded, is currently paying $2900 per battery.  The federal tax credit, which is 24% of the cost of installation, applies when your battery is charged 100% from your solar system.  When you use a generator, you do not have the option of these financial benefits.

Environment: Many customers tell me that they wish to install solar simply for the environmental benefits, namely reducing carbon emissions generated from the use of fossil fuel electricity.  If we look simply at operation, a solar system does not add carbon to our atmosphere.  On a local level, batteries increase the environmental benefits of solar.  Without batteries, solar produces electricity during the day, sending the majority of the production to the grid.  At night, electricity is then purchased from the grid.  If your utility is providing fossil fuel electricity, you are still using that at night.  Using battery storage, however, allows you to use the clean energy you produced during the day at night as well; you won’t have to purchase “dirty” energy. Generators, on the other hand, operate from fossil fuels and will continue to add carbon to our environment.

Noise:  Simply, batteries are silent; generators make noise.  Most generators make noise near the volume of an air conditioning condenser.  Do you need the sound of an additional air conditioner near your home?

Location:  A generator is a large piece of equipment that will take space near your home, usually about twice the size of an air conditioning condenser.  Batteries, however, hang on the wall.  They can be installed outside, perhaps near your electrical panel, or inside your garage.  Generators emit exhaust and can’t be installed in a garage, basement, or near a window.  Batteries are sealed and do not emit gases of any kind.

Maintenance:  Generators require annual maintenance, including oil changes.  They have lead acid batteries for auto-start.  They have many moving parts and will wear out with time.  Batteries do not require annual maintenance.  The Tesla Powerwalls are warrantied to have 70% of their battery storage at the end of 10 years.

In summary, for many reasons, batteries are superior to generators for whole house power backup.  If, however, you still desire a generator, we are happy to install that for you as well.  Please reach out to the team at Connected Technology and we will be happy to provide whole house power backup in any way you desire.

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