Choose a battery
Pick a brand, then how many batteries are installed or being considered.
What do you want to keep running?
Each item uses a typical amount per day during an outage, not running nonstop.
How carefully will you save power?
Saving power means using the items you picked less often.
Charging an EV during an outage
A home battery can power an EV charger, but a single charging session can use more energy than the rest of the house uses overnight. That's why EV charging is usually left out of backup plans, saving the battery for the fridge, lights, Wi-Fi and heating or cooling.
How this estimate is calculated
Backup time is the battery's usable energy, minus any EV charging, divided by the daily energy your selected items use. Saving power lowers that daily total by the percentage you pick.
Battery capacity stays the same year-round, but solar can refill the battery during an outage: faster on sunny summer days, slower in winter or under shade. This estimate doesn't count solar recharging, so it shows how long the battery lasts on its own.
Typical daily use per item
Battery specifications
About this planning tool
Is this a solar or battery proposal?
No. This is an educational planning calculator. It's not a formal proposal, engineering design, utility bill guarantee or financial promise.
Can I use this without installing solar?
Yes. You can use it to understand outage planning and backup time before deciding whether solar or battery storage is right for your home.
Why email my results?
It gives you a copy of your choices and results to review later, share with family, or use to start a more detailed conversation.
What's needed for a design specific to my home?
A detailed review looks at 12 months of PG&E usage data, roof layout, shade, electrical panel capacity, future EV or heat pump plans, backup goals and installation space.
About NRG Geek
NRG Geek is Robert Kelly's independent educational platform for practical Northern California guidance on solar, battery backup, EV charging, heat pumps and home electrification.
Every home is different. Electrical panels, appliance use, solar production, roof conditions and outage goals all affect battery sizing and backup design.
Privacy, legal and terms
How is my information used?
The Email My Results button opens your email app with your choices and results. Nothing is sent until you send it. If you ask for personal guidance, Robert may follow up. NRG Geek does not sell your personal information.
Is this a proposal or guarantee?
No. Results are estimates for educational planning and are not a proposal, engineering design, financial guarantee or utility bill guarantee.
Third-party links and brands
Tesla, FranklinWH and Enphase are trademarks of their owners. NRG Geek is not affiliated with these companies. Linked websites have their own privacy policies and terms, and NRG Geek is not responsible for their content.
Accuracy
Equipment specifications, PG&E rates, regulations and incentives change over time. Verify important information before making financial or construction decisions.
Copyright
© 2026 NRG Geek. All rights reserved. This calculator and its educational content may not be reproduced without written permission.