California Community Solar Share Payback Calculator

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How California community solar pencils out

California’s community solar landscape is finally expanding after years of pilot programs. The California Public Utilities Commission (CPUC) approved new community solar tariff structures in 2023, giving residents an alternative to rooftop panels. Programs such as PG&E’s Enhanced Community Renewables (ECR), Southern California Edison’s Solar Shares, San Diego Gas & Electric’s EcoShare, and Sacramento Municipal Utility District’s SolarShares let customers subscribe to remotely sited solar farms. Subscribers pay a per-kilowatt-hour fee for the energy block they reserve, then receive bill credits based on utility tariffs. The net savings depend on how subscription charges compare with bill credits, how quickly rates escalate, and whether enrollment or exit fees apply. Advertisers in this space—installers, subscription managers, and clean energy lenders—pay premium rates to reach homeowners and renters evaluating these decisions, making accurate calculators essential for EEAT.

The calculator first asks for your annual electricity consumption. Utilities publish 12-month summaries that make this easy to find. Next, enter the share size: what portion of your load you want the community solar project to cover. Most programs require at least 25% participation but allow oversubscription up to 120% so you can hedge future usage. The analysis horizon matches your contract or the period you want to evaluate; PG&E’s ECR contracts often run 20 years, while SMUD offers 10-, 15-, and 20-year options. The discount rate converts future savings into today’s dollars, supporting net present value (NPV) analysis.

Behind the scenes, we maintain a program database based on current tariffs. For PG&E ECR projects, we assume a baseline bundled rate of USD 0.32/kWh, a bill credit of USD 0.285/kWh tied to the Power Charge Indifference Adjustment (PCIA), and a subscription charge of USD 0.225/kWh. Enrollment fees average USD 250, and exit fees around USD 150 if you terminate early. Credits rise 2% annually, subscriptions 1.5%, and utility rates 3%. SCE Solar Shares uses a baseline of USD 0.29/kWh, a credit of USD 0.255/kWh, and a subscription rate of USD 0.205/kWh, with USD 150 enrollment and USD 100 exit fees. SDG&E EcoShare assumes a higher baseline of USD 0.36/kWh, credit of USD 0.31/kWh, subscription of USD 0.27/kWh, and higher escalation (3.2% baseline, 1.8% subscription, 2.2% credit). SMUD’s SolarShares charges USD 0.135/kWh with a USD 0.165/kWh credit against a baseline of USD 0.18/kWh, minimal enrollment (USD 50), and no exit fees thanks to the municipal structure. We also track marginal grid emissions: 0.32 kg CO₂/kWh for PG&E, 0.34 for SCE, 0.35 for SDG&E, and 0.25 for SMUD.

The model computes how many kilowatt-hours fall under the subscription by multiplying your annual usage by the share percentage. We then calculate year-one credits and subscription charges, subtract subscription costs from credits, and factor in enrollment fees. The baseline bill equals annual usage multiplied by the baseline rate. Program participation shifts your bill: unsubscribed usage still pays the baseline rate, credits reduce the remaining bill, and subscription charges add to it. If a program offers time-of-use adjustments, we approximate them using average rates.

Cash flow analysis uses a discounted cash flow (DCF) framework. The first-year net savings equal baseline bill minus program bill minus enrollment fees. Future years apply escalation rates to baseline, credits, and subscriptions. Some programs charge exit fees in the final year if you leave early; we include that cost in the final year, reducing cumulative savings. To express this mathematically, the NPV equation is:

In this formula, \(F\) is the upfront enrollment fee, \(S(t)\) is the annual savings in year \(t\), \(r\) is the discount rate, and \(E\) is the exit fee applied in the final year \(n\). The calculator evaluates each term to output NPV, internal rate of return (IRR), and payback period. IRR is solved numerically because subscription escalations and exit fees complicate closed-form solutions.

Let’s walk through an example using the default values. Suppose you consume 7,200 kWh annually and subscribe to 75% of your load through PG&E’s ECR. Year-one subscription volume equals 5,400 kWh. Credits worth USD 0.285/kWh generate USD 1,539, while subscription charges at USD 0.225/kWh cost USD 1,215. The baseline bill is 7,200 × 0.32 = USD 2,304. Under the program, you pay 1,800 kWh at the baseline rate (USD 576), add the subscription cost (USD 1,215), and subtract credits (USD 1,539), yielding USD 252. Add the USD 250 enrollment fee and your year-one cost becomes USD 502. Compared with the baseline USD 2,304, you save USD 1,802 in the first year. Over 20 years, escalating baseline rates and credits produce undiscounted savings of roughly USD 44,000. After applying a 4.5% discount rate, NPV sits around USD 24,700, and payback on the enrollment fee occurs within the first year. Because PG&E applies a USD 150 exit fee at term end, the final year cash flow subtracts that amount.

Switching to SCE’s Solar Shares changes the math. With baseline rates of USD 0.29/kWh, credit of USD 0.255/kWh, subscription of USD 0.205/kWh, and a 25% share (1,800 kWh), year-one credits total USD 459, subscription costs USD 369, and baseline bill USD 2,088. Program bill equals 5,400 kWh at baseline (USD 1,566) plus subscription cost (USD 369) minus credits (USD 459) plus enrollment fee (USD 150) for USD 1,626. Year-one savings come to USD 462. Because escalations are moderate, 20-year NPV lands near USD 5,200. Payback occurs in year one, but the IRR is lower (around 24%) because savings are smaller. The CSV output shows how credits and costs evolve, letting you evaluate what happens if SCE changes rates.

SDG&E’s EcoShare produces higher savings due to steep baseline rates. Using a 90% share (6,480 kWh), credits of USD 0.31/kWh generate USD 2,009, subscription charges at USD 0.27/kWh cost USD 1,750, and baseline bill is USD 2,592. Program bill nets USD 1,483 after credits, plus a USD 300 enrollment fee and USD 200 exit fee in year 20. NPV surpasses USD 19,000 with a 4.5% discount rate, while payback still occurs in the first year thanks to an immediate USD 1,109 savings. SMUD’s SolarShares, designed for Sacramento renters, offers modest but steady savings: USD 0.165 credits, USD 0.135 subscription, and USD 0.18 baseline produce year-one savings of USD 216 on a 60% share. The municipal utility’s no-exit-fee policy and shorter terms keep risk low.

Carbon benefits also matter. The calculator multiplies the subscribed kilowatt-hours by the utility’s marginal emissions factor and then assumes the community solar project delivers near-zero emissions. For PG&E, offsetting 5,400 kWh avoids roughly 1.73 metric tonnes of CO₂ in year one. Because California’s grid is already clean, emissions avoidance is lower than in coal-heavy states but still meaningful for corporate sustainability reporting.

The table below compares year-one metrics for each program using the default share (75% except where noted) to help you gauge relative performance.

Use the CSV export to support lender discussions or community solar contract reviews. Many subscription managers ask for payback modeling before approving transfers. You can also vary share size to see if oversubscribing makes sense. For example, subscribing to 110% of your load can lock in more credits if you expect to buy an EV, but exit fees may apply if usage falls. Investors evaluating ESG reporting can leverage the emissions data to quantify Scope 2 reductions.

Limitations: the calculator assumes credits and subscription charges escalate at constant rates, but utilities sometimes adjust tariffs mid-year. Programs may also include administrative fees not reflected here. Bill credits can depend on time-of-use periods; we average them, which may understate savings for peak-heavy households. Finally, we do not model federal tax incentives because community solar subscriptions typically do not qualify for residential tax credits in California. Always confirm terms with your provider before signing a contract. Still, this tool equips you with transparent numbers and exportable evidence to make confident decisions.