140,000 home batteries backed California's grid. Start with your Wi-Fi.

HoldBackup · Issue 1 · September 29, 2026

Disclosure: Some links in this email are Amazon affiliate links, marked "paid link." If you buy through one, HoldBackup may earn a commission at no extra cost to you. As an Amazon Associate I earn from qualifying purchases. HoldBackup has not lab-tested any product here. Product numbers come from the maker's spec sheets, and grid numbers come from the news sources cited below.

This is the first HoldBackup email. Once a week you get one thing to check, one thing worth buying, and what that thing won't do.

This week starts with a record. On the evening of September 9, during a California heat wave, home batteries sent more power back to the grid at once than ever before. Most people reading this don't own one of those batteries. So this issue covers the record first, then a small, inexpensive first step that works without one.

The Signal

More than 140,000 home batteries in California discharged to the grid over about three hours on the evening of September 9. Together they peaked above 580 MW. EnergyTech (Sep 22) and pv magazine USA (Sep 25) both report it as the largest residential virtual power plant dispatch on record. A virtual power plant is thousands of home batteries answering one call, so the grid can treat them as a single power source.

Where the 580 MW came from:

  • Tesla Powerwalls: 517 MW from about 110,000 units. Sunrun owns and operates 55% of them.
  • Other makers' batteries in Sunrun's fleet: 63 MW from more than 30,000 units.

The call came through the California Energy Commission's Demand Side Grid Support program, which dispatches enrolled batteries when day-ahead wholesale power tops $200 per megawatt-hour.

Now the honest part. If you're like most readers, you weren't one of the 140,000. A whole-home battery is a big purchase that needs an installer. You don't need one to stay connected through most outages, because most outages are short.

The HoldBackup order is simpler. Keep the modem and router on first. Add a power station for the fridge when you're ready to cover hours.

The Pick: APC BE600M1

Sold as: APC BE600M1 UPS Battery Backup & Surge Protector for Computer, Router, NAS

A modem and router draw about 10 to 30 W together. APC's own runtime chart gives this unit 1 hour 22 minutes at 33 W. Its five battery-backed outlets cover the modem, the router, and your provider's box, with room left for a switch. It weighs 7.69 lb and sits on a shelf.

Maker specs:

  • 600 VA / 330 W
  • Standby topology: switches to battery when the power fails, with no voltage regulation
  • Stepped sine wave on battery: fine for small power adapters, the wrong choice for a desktop with a big power supply
  • 5 battery-backed outlets, plus 2 surge-only
  • User-replaceable battery (APC APCRBC154)
  • Runtime from APC's chart: 1 h 22 min at 33 W, 52 min at 50 W, 23 min at 100 W

APC's chart assumes new, fully charged batteries, and runtime drops as the battery ages. HoldBackup has not lab-tested this unit. Your adapters' real draw sets your number.

Fits when

  • You're backing up the modem, router, and provider's box together
  • Your outages are flickers and short drops, which is most of them
  • Bulky adapters need room: there are five battery-backed outlets
  • You care more about light and inexpensive than long runtime

Falls short when

  • You want hours of Wi-Fi in a long outage. A portable power station is the tool for that.
  • Brownouts are frequent. A standby unit switches to battery instead of correcting the voltage.
  • The load is a desktop or anything sensitive to a stepped sine wave.
  • Your provider's network goes down too. A UPS can't bring that back. A phone hotspot is the fallback if cell service holds.

Store links (Amazon sets the price, and it changes):

Full specs, the runtime table, and when to swap the battery: A UPS for your router and modem

The Check: 15 minutes

Do this once, while the power is on.

  1. Find everything on the network path: the modem, the router, any box your internet provider installed, and any switch or main mesh unit.
  2. Read the output line on each power adapter and multiply volts by amps. That's the most the adapter can supply. Real draw is usually lower.
  3. Add them up. At 33 W, APC's chart gives the BE600M1 1 h 22 min. A lighter load runs longer.
  4. Already own a UPS? Make sure the network gear is plugged into the battery-backed outlets. Surge-only outlets turn off in an outage. Then run the self-test the manual describes.

No time for the math? A modem and router together sit far below the 330 W this unit is rated for. Plug them into a small UPS and you're covered for the short outages.

One more guide: the fridge

When you're ready for hours instead of minutes, the refrigerator is usually next. A kitchen fridge runs at about 100 to 250 W and pulls several times that for a moment when the compressor starts. A portable power station has to handle that startup surge and store enough watt-hours for the hours you need. With no backup at all, USDA says a closed fridge keeps food cold for about 4 hours.

The guide shows how to check both numbers before an outage: Running a refrigerator on a portable power station

Browse every guide (UPS units, power stations, and generators) at holdbackup.com.

Reply and tell us what you most need to keep on when the power goes out. It shapes what we cover next.

Disclosure: Store links marked "paid link" go to a HoldBackup /go/ address that counts the click, then to Amazon. If you buy through one, HoldBackup may earn a commission at no extra cost to you. As an Amazon Associate I earn from qualifying purchases. HoldBackup has not lab-tested these products. Runtime and specs are the maker's published figures. Full disclosure.

Sources: EnergyTech, Sep 22, 2026 · pv magazine USA, Sep 25, 2026 · APC BE600M1 runtime chart

HoldBackup: backup power only.

Keep reading

View more
caret-right
© 2026 HoldBackup.
beehiivPowered by beehiiv