Solar Cost by System Size

In short

• Average US residential system: 6.74 kW in 2024.
• It has grown every year since 2014, when it was 5.38 kW.
• State averages range from 5.16 kW to 12.59 kW — more than two to one.
• Size should be derived from your annual kilowatt-hours, then constrained by usable roof.
• Bigger is not automatically better where exports are compensated below retail.

How system size has changed, 2014–2024

Systems have grown steadily. Panels got more powerful, so the same number of modules carries more capacity, and households added air conditioning, heat pumps and electric vehicles.

System size by state, 2024

The spread is wider than most people expect, and it does not follow sunshine. It follows how much electricity households use, how much roof they have, and what the utility pays for exported power.

Where exports earn close to retail, sizing to annual consumption makes sense and systems are larger. Where they earn much less, sizing to daytime consumption makes more sense and systems are smaller.

How to size a system for your own house

Three steps, in this order. Reversing them is how people end up with a system sized to a budget rather than to a roof.

1. Pull twelve months of kilowatt-hours from your utility account. Not the dollar total — the energy. Bills move with rates and with weather; kilowatt-hours are what a system is sized against.
2. Convert to capacity. Divide your annual consumption by the annual production per installed kilowatt at your location, orientation and tilt. That ratio varies enormously across the country, which is why a rule of thumb from a national article is close to useless.
3. Constrain by usable roof. Not roof area — unbroken, unshaded, sensibly oriented planes after fire setbacks. This is frequently the binding constraint, and it is why two identical households get different systems.

Our system size calculator and panel count calculator do the arithmetic and show the formula, and how solar works covers what the components do. Rooftop solar explains what makes a plane usable.

What size does to the price

Size drives total cost, but not proportionally, because a significant part of a solar project does not scale with panel count.

• Scales with size: modules, racking, and some inverter capacity.
• Does not scale: permitting, the interconnection application, design, mobilising a crew, commissioning, and the trip itself.

So cost per watt generally falls as systems get larger, and a very small system carries its fixed costs inefficiently. That is the main reason a six-panel townhome array looks expensive per watt next to a neighbour's twenty-panel one. Cost per watt explains how to compare the two properly.

When bigger stops being better

Every kilowatt-hour you use as it is produced is worth your retail rate. Every kilowatt-hour you export is worth whatever your utility pays for exports, which may be far less.

Under full retail net metering those are the same, and sizing to annual consumption is rational. Under net billing or an avoided-cost buyback rate they are not, and a system sized to your annual total will send a large share of its output out at a low price.

In that situation a smaller system sized closer to daytime consumption — or the same system paired with storage — usually returns more per dollar spent. Net metering vs net billing sets out which you are on.

Common questions

What size solar system does the average US home install?

The average net-metered residential system installed in the United States was 6.74 kW in 2024, up from 5.38 kW in 2014. That is a HyreSolar calculation from Form EIA-861, dividing reported residential net-metered capacity by reported installations. It is a national average across every roof and every tariff, so it is a reference point rather than a recommendation.

How do I work out what size system I need?

Start with twelve months of kilowatt-hours from your utility account, not the dollar total. Divide by the annual production per installed kilowatt at your location and orientation, then check the result fits your usable roof plane. The order matters: consumption first, roof second, budget third.

Why do average system sizes differ so much between states?

They track consumption, roof space and export rules rather than sunshine. In 2024 the largest average was North Dakota at 12.59 kW and the smallest was Colorado at 5.16 kW — a difference of more than two to one between two places that both get plenty of sun.

Is a bigger system always better value?

No. Production you cannot use on site is only worth what your utility pays for exports, and that can be well below retail. Where export compensation is poor, a system sized to your daytime consumption often returns more per dollar than one sized to your annual total.

Method and limitations

Average size is reported residential net-metered capacity divided by reported residential net-metered installations, per state and per year, from the Form EIA-861 net metering schedule. EIA publishes both inputs; it does not publish this ratio. Our full methodology covers how the derivation was validated, and both tables on this page are downloadable as CSV.

What this does not tell you:

• It is a mean, so a small number of very large systems pulls it upward. There is no median in the source data.
• It counts net-metered systems only. Capacity under buyback, feed-in or utility-owned arrangements sits on a different schedule and is excluded.
• States with few installations produce volatile averages — read the systems column alongside the size.
• It is a snapshot of what was installed, not of what was optimal. It carries whatever sizing conventions and incentive rules applied at the time.
• EIA-861 lags by roughly two years. 2024 is the most recent final release.

Sources

• US EIA, Form EIA-861 — Net Metering (annual files, 2014–2024) Utility-level net-metered capacity, installations and energy sold back by state and customer sector, plus PV-paired battery capacity and installations from 2023. Downloaded as the published annual ZIP archives. Retrieved 2 September 2026
• US EIA, Form EIA-861 — Sales to Ultimate Customers (annual files, 2014–2024) Utility-level residential revenue, sales and customer counts by state, used to derive the average residential price and to count the households a state actually meters. Retrieved 2 September 2026

HyreSolar analysis of EIA data. Figures described as a HyreSolar calculation are derived by us and are not official EIA statistics. Data as of the Form EIA-861 2024 final release, retrieved 2 September 2026.