A few years ago most new home solar systems had no battery. Now a large share do. Wood Mackenzie counted 45 percent of U.S. home solar installs paired with storage in the first quarter of 2026, up from 38 percent a year earlier, and Lawrence Berkeley National Laboratory counts 37 percent for all of 2025, up from 25 percent in 2024. The growth follows the rules for exported solar. Where a utility cut what it pays for power sent to the grid, as California did, a battery became the common design. In most other states, fewer than one in 20 new home systems had a battery in 2024. A solar quote without storage can leave money on the table wherever export credits or time-of-use rates punish midday exports, and it can be the right design where they do not.
How NEM 3.0 in California changed the math overnight
California's Net Billing Tariff, often called NEM 3.0, was adopted in December 2022 (CPUC Decision D.22-12-056) and applies to new solar applications from April 15, 2023. Under the old rules, excess kWh were credited at close to the retail rate, and California's 2025 average residential rate was about 32.5 cents per kWh (EIA, preliminary). Under the new tariff, exported kWh earn the utility's avoided cost, which the California Public Utilities Commission says is usually lower than the retail rate, though it can rise above it on late summer evenings.
The economics flipped from "export everything and let the meter spin backward" to "use it yourself, because the grid pays less for it." Battery storage solves that directly. Panels charge the battery during the day. The household discharges it in the evening, when time-of-use rates are at their highest. The avoided grid purchases are the payback.
The attachment data shows how quickly homeowners respond. Berkeley Lab found California's home battery attachment rate rose from 14 percent in 2023 to 57 percent in 2024, following the change in its net metering rules. Hawaii went through the same shift earlier: its rate climbed from 2017 to 2021 after its own net metering changes and has held near 85 percent since. Other utilities have moved away from retail-rate export credits too. Arizona's largest utility, APS, credits exports from customers who apply between September 2026 and August 2027 at $0.05554 per kWh, down from $0.129 for its first group of customers in 2017 (APS Rate Rider RCP, Arizona Corporation Commission Decision 82122). Berkeley Lab reports large increases in battery attachment in Arizona and Texas in 2025.
Time-of-use rates reward stored solar
Time-of-use rates charge more for power in the late afternoon and evening than at midday. Solar makes plenty of power at noon, when the rate is low, and almost none at 7 p.m., when the rate is highest.
Without a battery, that solar gets exported during the cheap window and pulled back during the expensive one. Where exports are credited at a low value, the household pays peak prices for evening use while its daytime output earns far less.
A battery changes that. Solar charges the battery during the day, and the household uses the stored power during peak hours instead of buying it from the grid. Each stored kWh is worth the gap between the evening rate and the export credit. As an illustration, a battery that shifts 10 kWh a day across a 30¢ gap is worth about $1,100 a year. A smaller gap, or less evening use, shrinks that figure quickly.
Rate designs vary by utility, and there is no nationwide rollback of net metering. Check your own tariff for two numbers: what you are paid for exported power, and what you pay in the evening peak. The wider the gap between them, the more a battery is worth.
What a battery adds to the price
A battery is real money. In Lawrence Berkeley National Laboratory's 2026 Data Update, cash-purchase home systems installed with a battery in 2025 had median prices about $2.10 per watt of solar above solar alone. On the 7.7 kW median home system, that works out to roughly $16,000. Most of the paired-system price data comes from California, and the median home battery held 13.5 kWh, the size of a single Tesla Powerwall.
Payback depends on that price against the yearly value of the power it shifts. Using the illustration above, a battery worth about $1,100 a year would take well over a decade to recover $16,000, while a wider rate gap or a lower price shortens that. A battery also keeps essential circuits running in an outage, which has value no bill calculation captures.
Whoever designs your system should size the battery against your actual evening use and your utility's peak window, rather than recommend the largest unit on the shelf. Usable kWh and depth of discharge matter more than nameplate capacity.
How Section 48E can lower the cost of a battery in a lease or PPA
The federal tax landscape changed sharply at the end of 2025. Section 25D, the 30 percent credit homeowners claimed on cash and loan-purchased solar and battery systems, expired December 31, 2025. Anything purchased outright after that date no longer carries a federal credit.
Section 48E is different. It's a commercial credit that flows to the company owning the system, which means lease and PPA structures can still capture 30 percent on solar and battery costs under current law. The solar portion carries a deadline: a solar project that begins construction after July 4, 2026 must be placed in service by December 31, 2027. The battery falls under the separate storage schedule, which runs into the 2030s. Projects that begin construction after 2025 also face new rules on material assistance from prohibited foreign entities. The provider takes the credit and can pass part of its value to the homeowner through a lower lease or PPA price.
This creates an unusual asymmetry. For a 2026 customer paying cash or financing the system themselves, the battery has to justify itself purely on TOU and self-consumption savings. For a customer using a lease or PPA, the company that owns the system can claim the credit on the battery and price part of that value into the contract. That can make a battery cheaper to add inside a lease or PPA than on a cash purchase.
What this means for a 2026 solar quote
Whether a solar-only proposal leaves money on the table depends on your utility. Where exported power earns far less than evening power, as under California's NEM 3.0, a battery is now the common design, and the attachment data reflects it. Where a utility still credits exports at or near the retail rate, solar alone can still be the better value, and a battery earns its place mainly through backup power.
Attachment is rising outside the early markets too, with Arizona and Texas up sharply in 2025. Rules can change, so ask how the proposal would hold up if your utility moved to a lower export credit during the life of the system.
If you're comparing proposals, ask whoever quotes your system to price two designs, solar-only and solar-plus-battery, against your actual utility tariff. Look at the battery's added cost next to the yearly value of the power it shifts and the backup it provides. If the battery cannot justify itself on those terms, it may be the wrong size or the wrong fit for your rate plan.