VPP events and backup power: will my battery be empty?

The short answer

Programs are designed so they don't use your whole battery. Most set a minimum reserve that stays in the battery for backup, and they limit events to certain seasons, days and hours. The details differ, so it's worth checking before you sign up.

Events happen at set times

Most programs dispatch batteries in late afternoon and evening, when demand peaks. ConnectedSolutions in Massachusetts runs events between 3 and 8 pm from June through September, each up to 3 hours, on up to 60 days a summer ^[1]. Sunrun's CalReady dispatches from 4 to 9 pm, May through October ^[2].

Reserves keep some charge for you

Many programs keep a share of the battery untouched. Sunrun says CalReady customers with outage protection keep at least 20% of their battery reserved for backup ^[2]. On Tesla's Texas plan, Powerwalls don't dispatch below the backup reserve the owner sets ^[7], and Tesla's 2026 Powerwall lease bundle reserves at least 20% for outages ^[3]. Base Power says its battery keeps backup in reserve while it supports the grid ^[4].

You may be able to opt out

Some programs let you skip events. National Grid says ConnectedSolutions customers can opt out at any time ^[6]. If a storm is coming, ask whether you can, and whether skipping affects your payment.

Questions to ask

What is the minimum reserve, and can I raise it?
What months, days and hours can events happen?
Can I opt out of an event, and what does it cost me?
If a company owns the battery, what backup does the agreement promise?

Questions people ask

Can a VPP use 100% of my battery?

Most programs keep a reserve. Sunrun CalReady keeps at least 20% for customers with outage protection, and Tesla's Texas plan won't go below the backup reserve the owner sets. Check your own program's reserve before enrolling.

When do VPP events usually happen?

Usually on summer afternoons and evenings when demand peaks, for example 3 to 8 pm in Massachusetts' ConnectedSolutions and 4 to 9 pm in Sunrun's California program.

Sources

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