If you’re a homeowner venturing into the solar power world for the first time, you may have a variety of questions. One of the single most common for those in this position: How many solar panels do I need for my home?
At Intermountain Wind & Solar, we’re proud to offer comprehensive residential solar panel installation services for all our clients, from consultation and design of your system to full installation of all components, including the Tesla Powerwall system. Some homeowners also pair solar panels with battery storage systems to provide backup power during outages and maximize energy independence.
We work with clients during the consultation and design phases to help them understand all the basics of our services plus their own solar needs, including how many panels their setup will require and the best ways to optimize the system to meet your goals. This two-part blog series will go over the basic steps we’ll take you through to calculate the power amount you need and the number of solar panels required to provide it, plus some other basics that help you attain a strong return on your solar investment.
Firstly, it’s good for homeowners to have a general idea of the typical solar power needs of standard homes, just as a baseline moving forward. Average homes tend to require between 15 and 30 solar panels, depending on electricity usage, roof space, panel wattage, and energy goals. The number might be on the lower end if you’re only using solar for certain power areas. And of course, these numbers can vary significantly if your home has special power needs or considerations, or is much larger or smaller than the average residence.
Modern residential panels commonly produce 400–450 watts each, which means:
As electricity rates continue to rise across parts of Utah and Idaho, many homeowners are using solar to stabilize long-term energy costs and reduce reliance on utility companies.
Our next several sections will detail exactly how we’ll help you calculate your needs.
For starters, before determining how many panels you need, you must identify your home’s current level of electricity usage. This is measured in Kilowatt Hours Used, abbreviated kWhs, which is the primary metric utility companies use (you’ll also see kWh used). The best way to do this is to obtain your electricity bill over the last six to 12 months, then break it down into hourly, daily and yearly energy usage. Looking at a full year helps account for seasonal changes like air conditioning, heating, and holiday energy use.
To keep it simple, many Utah households use approximately 14,000–15,000 kWh annually, while Idaho homes often average around 11,000 kWh per year, though usage varies widely depending on home size and appliances.
Here’s an easier example:
If your home uses 12,000 kWh annually:
This number becomes the foundation of your solar design.
What one solar panel actually does:
For reference, a modern residential solar panel (around 400-450 watts) typically makes:
To lay it all out in one simple line:
3 × 400 watt panels = about 1.2 kilowatts (1,200 watts) = about 5–7 kWh per day in Utah/Idaho (average)
To make sense of the terms:
Once you have a firm grasp on your home’s power usage, determining how much power you need is simpler. The next step is figuring out how many hours of direct sun exposure will be present for the panels to be installed on your home. Homes that face the sun and have few or no obstructions can expect high energy production on a per-panel basis, while those that are partially blocked at times will produce less.
Solar systems do not generate power evenly all day long. Instead, production is based on peak sun hours, periods of strong sunlight capable of producing maximum panel output.
Because Utah and Idaho receive abundant sunshine, solar performs especially well here.
On average:
These numbers give installers a baseline for estimating how much energy a solar system can generate over the course of a year. In real-world system design, installers also account for roof direction, shading, and system efficiency losses (inverter + temperature + wiring losses), which slightly adjust total expected production from these peak sun hour estimates.
A south-facing, unshaded roof in Utah or Idaho will generally perform near the higher end of production estimates, while east- and west-facing roofs or shaded roofs will produce less and may require slightly more panels to offset the same energy usage.
Once your annual electricity use and solar production potential are known, calculating panel count becomes much easier.
A properly installed 1-kilowatt (kW) solar system in Utah often generates roughly 1,500-1,750 kWh annually, depending on roof angle, orientation, and shading.
With today’s residential solar panels typically rated around 400-450 watts each, a 1 kW solar system usually consists of about 2-3 solar panels.
If your home uses approximately 12,000 kWh annually, you may need a solar system around 7-8 kW in size to offset most of your electricity usage in Utah or Idaho conditions. Using modern 425-watt panels, that would equal roughly 18-20 solar panels, depending on sunlight exposure, roof orientation, and system efficiency.
Example Solar Panel Calculation:
If your household uses 12,000 kWh annually and each installed kilowatt of solar generates around 1,600 kWh per year, you would need approximately:
12,000 ÷ 1,600 = 7.5 kW solar system
Using today’s common 425-watt solar panels, that equals roughly:
7,500 watts ÷ 425 watts per panel = about 18 panels
For more on determining how many solar panels your home needs for a new solar installation, or to learn about any of our services, speak to the staff at Intermountain Wind & Solar today.
Modern residential solar panels usually produce between 400 and 450 watts each. Because Utah and Idaho receive strong sunlight throughout much of the year, a properly installed 1-kilowatt solar system can often generate approximately 1,500-1,750 kWh annually. Actual production depends on roof direction, shading, weather, and system design.
Some of the biggest contributors to high electricity bills include air conditioning systems, electric heating, water heaters, EV charging, hot tubs, pool equipment, and older appliances. Hot tubs in particular can significantly increase monthly energy usage because they require continuous heating and circulation. Homes with these higher energy demands often require larger solar systems to fully offset electricity costs.
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