That’s two bills. And if you’re with PG&E, SCE or SDG&E, someone has probably told you the fix is a battery.
It sounds right. But for most homes I look at, a battery won’t fix it.
Here’s what a battery really does with your power, when it does help, and what actually fixes two bills.
Why you have two bills
Most of the time, it’s simple: your house uses more power than your panels make.
- The system was too small from day one. Some designs only covered part of your use on purpose. That’s called tier shaving.
- The house changed. Maybe you got an electric car, added AC, or more people moved in. An electric car alone can add about 3,000 to 4,000 kilowatt-hours a year.
Either way, the result is the same. You pay for the solar, and you still buy power from your electric utility company.
(There are a few other reasons a true-up gets big, like the 12-month clock and rate changes. I break all of them down here.)
Why a battery gets pitched so often
On NEM 1.0 or 2.0, adding a battery by itself doesn’t change your plan. So it’s the easiest thing to add.
And batteries are good equipment. I put them in a lot of my designs.
But easy to add doesn’t mean it fixes your problem. To see why, you have to know what a battery actually does.
What a battery actually does
A battery doesn’t make power. It stores power your panels already made.
Think of it like a bigger pantry. It’s great. But it doesn’t go grocery shopping for you.
Around noon, your panels fill the battery. In the evening, your house runs on it. So the battery moves power to a different time of day, but the total your panels make in a year stays the same.
You also lose a little on the way in and out. Most home batteries give back about 90 percent of what goes in. Tesla lists the Powerwall 3 at about 89% (solar to battery to home), and Enphase lists the IQ Battery 10C at about 90%.
The math on one example home
Here’s a simple, made-up example:
| Kilowatt-hours a year | |
|---|---|
| What the panels make | 8,000 |
| What the house uses now (after an electric car) | 11,500 |
| The gap you buy from the grid | 3,500 |
At about 35 cents per kWh, that gap costs around 1,200 dollars a year. (Average home rates in Q2 2026 were about 33.7 cents at PG&E, 34.4 at SCE and 45.5 at SDG&E, per the CPUC’s Public Advocates Office.)
Now add a battery. Your panels still make 8,000. The gap is still 3,500.
The battery just moves some of your 8,000 into the evening. And since it loses a little, the gap actually gets slightly bigger.
What the battery is worth in this house
So is the battery worth anything here? Yes, a little.
On NEM 2.0, the power you send out at noon earns the noon price. The power you buy at 6 PM costs the evening price. On SCE’s TOU-D-4-9PM plan in summer, weekday power is about 34 cents off-peak and about 58 cents from 4 to 9 PM.
Say the battery moves 10 kilowatt-hours into the evening every day, all summer. After the losses, that’s worth roughly 200 dollars.
That’s real money. But it’s 200 dollars against a 1,200-dollar gap. And a battery added to an existing system costs a lot more than 200 dollars a year saves. That’s a lot of money to make your true-up a little smaller.
When a battery IS the right call
To be fair, there are times a battery is exactly right:
- Your problem is timing, not size. Your panels make enough power over the year, but most of your use lands from 4 to 9 PM. If you’re on a time-of-use plan (every NEM 2.0 home is), a battery can cover some of those evening hours. But running your big appliances outside 4 to 9 PM is free, so try that first.
- You want backup when the power goes out. That’s a different reason, and a good one.
- You’re on NEM 3.0. Your exports earn only about 5 to 8 cents, so storing your power is worth a lot more.
- Your NEM plan is close to its 20-year end. NEM 1.0 and 2.0 last 20 years from your permission-to-operate date. After that, your home moves to the newer plan, and a battery starts to matter more.
If you’re with LADWP or another city-run electric company, your rules are different. Exports still earn close to full price there, so a battery is mostly for backup.
Step 1: Find your gap
So if a battery isn’t the fix, what is? It starts with one number most people have never seen: your gap. That’s how much more power your house used than your panels made over the last year.
You don’t have to do the math. Your electric utility company already did it.
- Log in to your online account with your electric utility company.
- Look for your net usage over the last 12 months. That’s your gap. Your true-up statement usually shows the same number.
- Don’t subtract your solar again. The meter already did that.
If that number is zero or less, you don’t have a gap. Your problem is timing (see above).
Then open your monitoring app. If your panels made a lot less than last year, you may just need a repair. If you lease your system, the company is usually responsible for repairs, so call them before you add anything.
Step 2: Add power, not storage
If the gap is real, the fix is more power. That means more panels.
But on NEM 1.0 or 2.0, there’s a limit. You can only add 1 kilowatt or 10 percent of your system, whichever is bigger. Go over that, and the whole system moves to NEM 3.0.
And 1 kilowatt doesn’t go far. In most of California, it makes about 1,500 kilowatt-hours a year (roughly 1,400 to 1,650). An electric car needs about 3,000 to 4,000. So that small add-on covers maybe half the car.
Two ways to add the power you’re missing
For most two-bill homes, there are two real ways to do it:
- Keep your current solar plan. You add a separate system that never sends power to the grid. With the options I offer, that separate system is a prepaid lease.
- A zero-down lease add-on. It adds the power you’re missing with nothing upfront, but it moves the whole home to NEM 3.0. So on PG&E, SCE and SDG&E homes, I design it with a battery. The new panels are the fix. The battery is there because NEM 3.0 pays so little for exports. This way is a good fit if you’d rather save each month than own more equipment, or if your NEM plan is close to its 20-year end anyway.
I run the numbers both ways. Then you pick. (Not sure which NEM plan you’re on? Start here.)
3 questions to ask before you buy a battery to fix your true-up
- "How many kilowatt-hours a year will this add?" For a battery alone, the honest answer is zero.
- "What’s my gap?" Ask them to show you the number.
- "What will my true-up be after this?" Ask for it in writing.
If the answer is a long pause, that’s your answer.
