Community & shared solar

Project size vs subscriber count tool

Work out how many households a shared array's capacity can support, or the array size needed for a target number of subscribers, either direction.

Your numbers

1 Which direction do you need?
2 Your numbers
Solar farm nameplate capacity in kilowatts. 1,000 kW equals 1 MW.
Typical fixed-tilt solar runs 15% to 25% depending on region. Use 20% if unsure.
Typical residential subscription averages 8,000 to 12,000 kWh a year.

How it works

Three steps to sizing the relationship

Step 1

Pick your known value

If you have the array's nameplate capacity, choose the first direction. If you're planning around a target subscriber count instead, choose the second.

Step 2

Use a realistic capacity factor

Capacity factor varies by region and panel orientation. If you don't have the array's actual figure, 20% is a reasonable estimate for a well-sited fixed-tilt system in most of the US and Canada. Confirm your subscription against the maximum subscription size tool once you know the total capacity.

Step 3

Cross-check against demand

If you're evaluating whether a waitlist is likely, compare the result here against the waitlist cost of delay calculator for what a long wait might cost you in lost savings.

Understanding the capacity to subscriber relationship

Why capacity factor is the key variable

A solar array's nameplate capacity in kW describes its peak output under ideal conditions, but actual annual output depends heavily on how much sun the site gets over a full year, captured by the capacity factor. A 5 MW array at 20% capacity factor produces roughly 8.76 million kWh a year, enough for around 800 typical residential subscribers. Capacity factor varies by region; check the DSIRE database for solar resource data specific to your state if you want a more precise figure than the general estimate used here.

What determines average subscription size

Average subscription size reflects both typical household usage and the offset percentage most subscribers choose. A program where most subscribers choose a 100% offset will support fewer total subscribers per megawatt than one where most choose a 50% offset, since each subscriber claims a larger or smaller share of the array's output. See the 100% offset calculator for how a full offset affects sizing. A net-zero rooftop system is sized around a similar full-offset target, covered by the panel count for a net-zero home tool.

Why this matters if you're on a waitlist

Understanding a project's total subscriber capacity helps explain why some programs have long waitlists even for seemingly large arrays. A project's subscriber capacity is fixed by physics and the array's size, so once popular programs fill up, new subscribers wait for either a new project or existing subscribers to leave. Check the waitlist cost of delay calculator to see what waiting actually costs in missed savings. The Department of Energy's community solar market trends data shows this capacity constraint is a real, documented driver of demand across the market, not unique to any one project.

Using this for project planning

Developers and municipal or nonprofit program organizers can use the reverse calculation to size a planned array against an expected subscriber base. Check the municipal solar program savings estimator if you're evaluating a city or town-run program specifically. A multi-building commercial portfolio faces a similar sizing exercise, covered by the multi-building portfolio solar sizing tool.

Questions

Frequently asked

A typical 5 megawatt community solar farm with a 20% capacity factor produces roughly 8.76 million kWh a year, enough to support around 800 subscribers at a 10,800 kWh average annual allocation. Actual subscriber counts vary based on the array's location, panel efficiency, and average subscription size.

Capacity factor is the percentage of a solar array's rated capacity it actually produces on average over a year, accounting for nighttime, weather, and seasonal variation. Most fixed-tilt solar arrays in the US and Canada run a capacity factor between 15% and 25%, depending on location and panel orientation.

Even a large array has a fixed subscriber capacity once you account for capacity factor and average subscription size, and popular programs can fill that capacity quickly. A waitlist usually means demand has outpaced the number of available subscription slots, not that the array itself is undersized for its design.

Generally yes, but the relationship isn't purely linear, since capacity factor and average subscription size both affect how many subscribers a given array size can support. A larger array in a lower sun region can support fewer subscribers than a smaller array in a stronger sun region.

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