Subscribing to an Array on Somebody Elses Field
Most households cannot install panels, because they rent, have the wrong roof, or live in a building. Community solar lets them subscribe to a share of an array somewhere else and receive credit on their bill.
The Population Rooftop Solar Cannot Reach
Rooftop solar requires owning a suitable roof. That excludes renters, apartment residents, households with shaded or poorly oriented roofs, and anyone who cannot fund or finance an installation.
Estimates suggest that a majority of American households fall into at least one of those categories, which is a substantial constraint on how far distributed solar can spread.
Community solar addresses it by separating the panels from the household. A larger array is built somewhere with suitable land and a grid connection, and households subscribe to a share of its output.
How the Credit Works
The subscriber is not physically connected to the array and does not receive its electricity. The arrangement is entirely a billing mechanism.
The array feeds its output into the grid. The utility calculates the subscriber share of that output and applies a credit to their electricity bill under a virtual net metering or bill credit programme. The subscriber pays the array operator for their subscription, at a price set below the credit value.
| Flow | Direction |
|---|---|
| Array generates and exports to the grid | Operator to utility |
| Utility applies bill credit to subscriber | Reduces the electricity bill |
| Subscriber pays the operator | Less than the credit received |
| Subscriber net position | The difference, typically 5 to 15 percent |
The saving is the gap between the credit the utility grants and the price the operator charges. Both sides of that gap are set by policy and contract rather than by anything physical, which is why the same array can be a good deal in one state and impossible in another.
The Credit Rate Is Everything
The economics rest entirely on how the utility values the exported generation, and states have used several approaches.
Crediting at the full retail rate is most favourable to subscribers and most contested by utilities, which argue that retail rates include transmission, distribution, and fixed costs the array did not avoid.
Crediting at an avoided cost or wholesale rate reflects only the energy value and is generally too low to support a subscription business.
Several states have adopted a value of solar methodology, attempting to calculate the actual benefit including avoided energy, avoided capacity, avoided transmission losses, and environmental value, which is analytically defensible and produces years of proceedings.
The critical risk for subscribers is that the rate can change. Programmes have been revised, capped, or closed to new entrants after projects were built and subscribers enrolled, which is a policy risk sitting inside what looks like a simple utility bill arrangement.
The Consumer Protection Issues
Because subscribers sign multi year contracts for a financial arrangement they cannot inspect, the sector has attracted attention from consumer regulators.
The recurring problems are long contract terms with substantial cancellation fees, transferability when a subscriber moves out of the utility territory, escalators raising the subscription price annually at a rate that may exceed electricity price growth, and credit requirements that exclude the low income households the programmes frequently claim to serve.
Several states have responded with standard disclosure requirements, caps on cancellation fees, and portability rules. Programmes designed specifically to serve low income subscribers typically require a share of capacity to be reserved for them and remove credit checks, which addresses the access problem directly.
Why Developers Like It
From the project side the model is attractive for reasons unrelated to households.
Building one array of a few megawatts is far cheaper per unit of capacity than installing hundreds of rooftop systems, and the array can be sited where land is cheap and solar resource is good rather than wherever the customer happens to live.
Customer acquisition is the principal cost and the principal risk, since a project needs subscribers for its full capacity and losing them requires replacement. Subscriber churn is the operating metric that matters most, and it is why developers pursue anchor subscribers such as municipalities and large commercial accounts to fill a substantial share before marketing to households.
What a Subscriber Should Check
The useful questions are narrow. What credit rate applies and whether it is guaranteed for the contract term or subject to programme change. What the subscription price is and whether it escalates. What happens on moving, both within and outside the utility territory. What the cancellation terms are. And whether the array is built and operating, since subscriptions are sometimes sold before construction.
The saving is real and modest. Anyone told to expect large reductions is being sold something other than the arithmetic.
The Bottom Line
Community solar extends distributed generation to the majority of households that cannot install panels, and it does so through a billing arrangement rather than a wire. The entire economics sit in the gap between the credit the utility grants and the subscription price, both of which are policy determined, which makes regulatory change the principal risk in a product that presents itself as a straightforward saving. The consumer protection failures have been about contract terms rather than about the concept, and the states that fixed the terms have functioning markets.