If you’re looking for a solar system for your house, you want to think in terms of power output in kWh. To maximize your financial savings, the optimal-sized solar array is one with a large enough power wattage in watts/kW to match your household’s energy usage.

Let’s take a closer look and see how this works in practice.

What is a solar array?

“Strictly speaking, a solar array only encompasses the ensemble of solar panels, the visible part of the PV (photovoltaic) system, and does not include all the other hardware, often summarized as balance of system (BOS),” says Wikipedia. “Moreover, PV systems convert light directly into electricity and shouldn’t be confused with other technologies, such as concentrated solar power or solar thermal, used for heating and cooling.”

How do I calculate the right size solar array for my home?

One way to estimate how many solar panels you will need is to use a solar calculator. To receive a tailored estimate, you would need to enter the following basic info:

The calculator then gives you an approximate system size in kilowatts, annual production in kilowatts, and the long-term profit (savings less cost of the system).

See how much solar panels will cost for your home

How many solar panels are needed to power a house?

In 2018, monthly average electricity usage in California was 547kWh. To match that energy requirement, a 4.23kW system solar system is required. This works out to 15 sixty-cell (275-285 watt) solar panels or 12 seventy-two-cell (350 watt) solar panels.

A 2,000-square foot home in California may need 23 sixty-cell panels, or 18 (larger) seventy-two-cell solar panels to be energy efficient. Because every house is different, shading and roof slopes vary, and because some families use more energy than others, the number of solar panels your home needs is you-specific.

What is the minimum roof size for solar panels?

An average solar panel is 65″x39″ (5.41’x3.25′) or 17.5 square feet.

Let’s look at the average California home. They would require 262.5 square feet for standard-efficiency 60-cell solar panels, or just 210 square feet for the more efficient (but costlier) high-efficiency 72-cell solar panels.

Factors like shade and roof orientation can affect calculations. Shade on your roof can reduce the output of your solar array, necessitating more solar panels to achieve the same output. It’s the same if your panel doesn’t face south.

And then there are regulations. California there is a safety ‘setback’ requirement of 3 feet. Your state’s and county’s building and safety requirements are important; so, consulting with a local solar array professional is the best advice.

There’s no cookie-cutter solution to what kind of solar array your home needs.

For DIYers: What’s the average size of a residential solar system?

A professional will be able to help you with design, will be able to get higher quality products and materials at a lower rate, and will also be useful in acquiring permits and tax credits. – HomeAdvisor

There is no ‘average’ size of a residential solar array. You can buy DIY (do-it-yourself) kits from 2kW up to 10kW. The savings of a DIY kit are negligible, and the risks are very tangible.

If you do not have a professional electrician installing your solar array, there is a good chance you might incorrectly set up the system and/or use sub-par materials, voiding all warranties and possibly the insurance as well. You might also fail to qualify for local or federal tax credits. In the worst-case scenario, a deadly fire could be caused because of faulty installation.

How much can a 2020 solar system cost?

As of March 2019, the typical 6kW solar system costs $19,080 bnefore incentives. This is down from the $40,000 an average-size residential solar systems cost in 2010.

What’s more important is your investment will yield measurable return on investment (ROI) results. A 6kW system in Los Angeles, California currently proves 25-year profit (savings less cost) of $41,413. And if your system is larger than average, your savings will be even bigger.

Can I get solar system discounts?

If you consider tax credits to be a discount–if you’re a taxpayer there’s no reason not to–then you can automatically save money on solar arrays through December 31, 2021.

The federal investment tax credit (ITC), popularly known as the federal solar tax credit, currently offers 26% off all solar systems installed before December 31, 2020. After that, the discount will to decrease to 22% in 2021. From 2022 onwards there will be no tax credit available to residential solar customers.

The fact that this 26% tax credit is available will help you get a quick payback and is a great reason to go solar now. 

There are also, city, county, and state initiatives, so other discounts may be available in your community. Thanks to supportive state legislation, many energy companies also offer rebates, discounts, or incentives for installing residential solar arrays.

Solar-Estimate has a database of the various solar incentives available in each state. Their advanced solar calculator also takes these into account when showing you the estimated cost for a solar system for your home. Finally, you can contact your local solar systems company to ask if there are additional discounts available for 2020.

Calculate the size of the solar panel system you need to power your house