California's transition from NEM 2.0 to the Net Billing Tariff, commonly called NEM 3.0, fundamentally changed the economics of commercial solar installations across the state. Under the previous regime, solar systems exported excess generation to the grid and received near-retail credits, making solar alone a compelling investment. Under NEM 3.0, those export credits were slashed by approximately 75 percent, dropping from an average of 30 cents per kWh to roughly 8 cents per kWh depending on the time of export and the utility.
This single policy change transformed the California commercial solar market from a solar-first model to a solar-plus-battery model almost overnight. Battery attachment rates for new commercial solar installations jumped from roughly 15 percent under NEM 2.0 to over 70 percent under NEM 3.0. The reason is straightforward: if exporting solar to the grid earns only 8 cents per kWh, but storing that solar in a battery and using it during peak hours avoids paying 50 cents per kWh, the battery's value proposition is clear.
For commercial building operators evaluating solar investments in California, understanding the NEM 3.0 economics is essential. The old rules of thumb no longer apply, system sizing considerations have changed, and the financial modeling now revolves around self-consumption and peak shaving rather than maximum export. This article walks through the new economics, the role of battery storage, the grandfathering provisions that are approaching their deadline, and how to evaluate a solar-plus-battery investment for your building or portfolio.
What Changed Under NEM 3.0
The Net Billing Tariff, which took effect on April 15, 2023, replaced the one-to-one retail credit structure of NEM 2.0 with a system that values solar exports based on the “avoided cost calculator,” a formula that estimates what the utility would have paid to generate or procure that electricity from another source at that specific hour. During midday hours when solar production is highest but grid demand is moderate, the avoided cost values are at their lowest, often 4 to 8 cents per kWh. During evening peak hours when the grid is strained, avoided cost values rise to 15 to 25 cents, but that is precisely when solar production is dropping to zero.
Monthly true-up replaced by instantaneous netting. Under NEM 2.0, excess solar generation in one hour could offset consumption in another hour within the same billing period. NEM 3.0 moves to instantaneous netting: each moment of export is valued at that moment's avoided cost rate, and each moment of import is charged at that moment's retail rate. There is no rolling credit bank within the month.
Non-bypassable charges now apply. Under NEM 2.0, solar customers were exempt from many per-kWh charges on their net imports. NEM 3.0 applies non-bypassable charges of approximately 2 to 3 cents per kWh on all grid imports, regardless of solar generation. This further erodes the net savings from solar-only systems.
Grid participation charge. NEM 3.0 introduced a monthly grid participation charge for solar customers, approximately $8 to $15 per month for residential systems and higher for commercial installations based on system size. While small in absolute terms, this charge represents another shift away from the solar-friendly policies of the NEM 2.0 era.
Why Batteries Changed Everything
Under NEM 2.0, a commercial solar system was sized to maximize annual production relative to annual consumption. Excess midday generation was exported at near-retail credits, so oversizing carried minimal economic penalty. Under NEM 3.0, every exported kWh earns only a fraction of its avoided-import value, so the optimal strategy is to consume as much solar generation on-site as possible and store the rest for use during peak hours when grid electricity is most expensive.
A battery system paired with solar captures the midday surplus, when production exceeds the building's real-time demand, and discharges it during the 4-to-9 PM peak window. Instead of exporting at 6 cents per kWh, that energy is used to avoid importing at 50 cents per kWh. The effective value of each stored kWh is the difference between the peak import rate and the marginal cost of storage, which for modern lithium-ion systems works out to roughly 3 to 5 cents per kWh in degradation and round-trip efficiency losses.
Commercial Battery Sizing
For a typical commercial building, battery sizing under NEM 3.0 is driven by two factors: the amount of excess solar generation available for storage and the building's peak-period consumption. A 500 kW solar system on a 200,000 square foot office building might generate 2,500 kWh during the midday hours that exceeds the building's simultaneous demand. A battery system of 500 kWh to 1,000 kWh can capture most of this surplus and discharge it over the five-hour peak window.
The battery also provides demand charge reduction by capping the building's draw from the grid during peak hours. If the building peaks at 400 kW during the 4-to-9 PM window, a battery discharging at 100 kW reduces the measured peak demand to 300 kW, saving $300 to $500 per month in demand charges. This demand charge savings stacks on top of the energy arbitrage value and can represent 30 to 40 percent of the battery's total economic benefit.
Grandfathering Provisions and Deadlines
Systems that received Permission to Operate under NEM 2.0 before April 15, 2023, are grandfathered under the NEM 2.0 tariff for 20 years from their interconnection date. This means a commercial system that went online in March 2023 will continue receiving near-retail export credits until 2043. This grandfathering provision has created two tiers of solar economics in California, with NEM 2.0 systems significantly more valuable than equivalent NEM 3.0 systems.
For building operators who already have NEM 2.0 systems, the grandfathering is secure but not unlimited. Any significant modification to the system, such as increasing its capacity by more than 10 percent, can trigger a transition to NEM 3.0. Even routine panel replacements should be documented carefully to avoid inadvertently exceeding the modification threshold.
Adding a battery to an existing NEM 2.0 system is possible without losing grandfathering status, provided the battery does not export to the grid. This creates an interesting optimization opportunity: NEM 2.0 systems can continue exporting surplus solar at near-retail credits while simultaneously using a battery to reduce peak demand charges. The combination of grandfathered export credits and battery-based demand management can produce returns that exceed either strategy alone.
Financial Modeling for Solar-Plus-Battery Under NEM 3.0
The financial analysis for a NEM 3.0 commercial solar-plus-battery system is more complex than a simple solar payback calculation. The key revenue streams include avoided energy imports during peak hours (valued at the peak TOU rate), demand charge reduction from battery discharge during peak demand windows, and demand response program revenue if the battery is enrolled in a utility or ISO program.
On the cost side, the analysis must account for the solar installation cost (typically $2.50 to $3.50 per watt DC for commercial scale), battery cost ($400 to $600 per kWh installed for lithium-ion), annual operations and maintenance, battery degradation over the project lifetime, and financing costs. The federal Investment Tax Credit at 30 percent under the Inflation Reduction Act significantly improves project economics, and California's Self-Generation Incentive Program can add further rebates for battery installations.
Under current California rate structures and incentive levels, a well-designed commercial solar-plus-battery system typically achieves a simple payback of five to eight years with an internal rate of return of 12 to 18 percent. Systems in SDG&E territory, where rates are highest, tend to pencil out fastest. PG&E territory follows closely, while SCE territory projects take slightly longer to reach payback due to different demand charge structures.
Portfolio-Level Solar-Battery Strategy
For portfolio operators with multiple California buildings, the decision is not simply whether to install solar-plus-battery but where and in what order. Not every building in a portfolio is equally suited for solar. Factors that drive prioritization include roof condition and available area, current electric rate schedule and TOU period alignment, building load profile and self-consumption potential, remaining lease term and ownership structure, and local permitting and interconnection timelines.
Start by screening the portfolio for buildings with large, unshaded roofs, high electricity costs per square foot, and load profiles that align well with solar generation curves. These are the buildings where solar-plus-battery delivers the strongest returns. Buildings with complex roofs, heavy shading, or low electricity costs should be deferred or evaluated for community solar subscriptions as an alternative.
Aggregating procurement across multiple installations can reduce per-unit costs for both solar panels and battery systems. Developers and EPCs typically offer volume discounts for multi-site contracts, and the reduced due diligence cost of working with a single building owner across multiple sites can translate into lower installed costs of 10 to 15 percent compared to individual projects.
What Commercial Building Operators Should Do Now
If you have existing NEM 2.0 systems, protect your grandfathering status by documenting any system modifications carefully and avoiding capacity increases above the 10 percent threshold. Evaluate adding batteries to capture demand charge savings without jeopardizing your export credit structure.
If you are evaluating new solar installations, model the economics with battery storage from the start. Solar-only systems under NEM 3.0 are rarely competitive with solar-plus-battery systems because the self-consumption and peak-shaving value of the battery typically outweighs its incremental cost within the first three years. Size the solar system to match daytime consumption rather than total annual consumption, and size the battery to capture the midday surplus and discharge during peak.
Finally, track the regulatory landscape. The CPUC continues to refine NEM 3.0 implementation details, and the avoided cost calculator is updated annually. Export credit values may change, demand charge structures may evolve, and new incentive programs may emerge. Buildings with centralized utility data management are best positioned to respond quickly when the economics shift, whether that means accelerating a battery installation or adjusting the dispatch strategy of an existing system.
Under NEM 3.0, the question is no longer whether to add batteries to commercial solar. The question is how large the battery should be and how quickly it can be installed to capture the peak-rate arbitrage opportunity that California's TOU structure creates.