How Many Solar Panels Do I Need in 2026?

How Is Solar System Size Estimated?

A planning-level solar sizing estimate starts with your annual electricity use and an estimate of how much electricity one kilowatt of solar can produce at your location.

Dwellvance uses modeled solar production to estimate the production-per-kilowatt value. The result is intended to help a homeowner understand the approximate system size that could offset their electricity use. It is not a final engineering design.

Step 1: Start With Your Annual Electricity Use

Your annual electricity consumption is one of the most important inputs in solar sizing. A home that uses more electricity will generally require a larger solar system to produce the same percentage of annual consumption.

The best starting point is actual utility usage rather than a rough household assumption. If your calculator input is based on estimated usage, the resulting system size should also be treated as an estimate.

Step 2: Estimate Solar Production at Your Location

Solar production varies by location and system characteristics. Dwellvance uses NREL PVWatts to model expected electricity production from a grid-connected photovoltaic system.

The production model uses location and solar-system inputs to estimate monthly and annual AC electricity production. Dividing annual production by system size produces the planning value used for solar sizing.

Dwellvance also applies a 14% planning system-loss assumption in its solar production methodology. This is a planning assumption, not a guarantee of the losses for a particular installation.

How Many Panels Does That Mean?

System size is normally expressed in kilowatts, while individual solar panels are rated in watts. Once a target system size is estimated, an approximate panel count can be calculated from the panel wattage.

For example, a 6 kW system using 400-watt panels would require approximately 15 panels. This is only a mathematical conversion; the actual number of panels that can fit on a roof depends on the roof layout, setbacks, obstructions, equipment, and the selected panel.

Does Roof Orientation Change Solar Sizing?

Yes. Roof orientation can affect how much electricity a solar array produces. The Dwellvance solar calculator collects roof orientation as part of the planning inputs so homeowners can provide relevant information about their roof.

However, homeowners should not interpret an online orientation selection as a substitute for a site-specific solar design. Roof pitch, azimuth, usable roof area, obstructions, equipment placement, and other installation details can affect the final design.

What About Shading?

Shading can reduce solar production, so it is an important part of a real solar assessment. Dwellvance collects a homeowner's shading selection, but the current planning methodology does not apply a verified quantitative shading adjustment to production.

That distinction matters. A shading selection in the calculator should not be interpreted as a precise percentage reduction in annual production.

Does a 100% Offset Always Make Sense?

No. A 100% annual electricity offset is a useful planning target, but it is not a universal recommendation for every homeowner.

Utility rules, export compensation, roof constraints, future electricity consumption, system costs, incentives, and project goals can all affect the appropriate system size.

Dwellvance's current sizing calculation uses annual electricity usage divided by modeled production per kilowatt to estimate the system size needed for a 100% annual production target. Treat that result as a planning estimate rather than a required system size.

What Can Make Your Final System Smaller or Larger?

Solar Sizing Example

Suppose a home uses 10,000 kWh of electricity per year and the modeled location produces 1,500 kWh per year for each kilowatt of installed solar.

The planning estimate would therefore be about 6.7 kW for a 100%-annual-offset target under those assumptions. This example is illustrative only and does not represent a recommendation for a particular home.

Why Solar Production and Solar Savings Are Different

Producing electricity does not automatically mean that every kilowatt-hour has the same financial value. Solar savings depend on how much electricity is consumed by the home, the applicable retail electricity rate, and how exported electricity is compensated.

Dwellvance therefore separates solar production from the financial savings calculation. If a verified electricity rate is unavailable, the calculator can provide production information without presenting unsupported savings or payback figures.

Use the Solar Calculator for a Planning Estimate

If you know your annual electricity usage, the Dwellvance Solar Calculator can combine that information with modeled production to estimate a planning-level system size. You can then explore estimated production, potential savings, installation cost, incentives, and simple payback when the required financial inputs are available.

Frequently Asked Questions