How Many Solar Panels Do I Need?

home solar panels rainbowOnce people find out how affordable home solar power can be, and how many advantages there are to choosing solar energy, the next questions are often “How many solar panels do I need?” and “How much do solar panels cost?”

As far as the cost of solar, we’ve previously shown that it can be 2 to 100 times cheaper than you might think, and that it’s possible to save about $20,000 with solar over 20 years in energy costs, and we showed you which states have the best return on investment for home solar systems.

So when it comes to answering the question “How many solar panels do I need?”, we’re not going to try to pull a fast one on you and pretend we know exactly how many solar panels you’ll need, because the real answer goes something like this: It all depends.

No, we’re not waffling or trying to avoid the question with that answer, because it really does depend on a number of factors that can vary wildly by location and demand.

The average amount of electricity used every day, and the average monthly electrical consumption, will be very different for different homes, and the potential solar capacity from a solar PV system will also vary, depending on the weather patterns and amount of solar insolation at the location.

For instance, an average home with mostly electric appliances (water heater, air conditioner, stove, dishwasher, clothes washer and dryer, refrigerator and freezer, power-hungry media and entertainment devices – especially those that are always on), will have a much higher overall electrical demand. For that same home, if it’s located in a different location, such as Arizona, will have a much higher electrical demand during the day for air conditioning than if it’s located in a cooler climate.

In contrast, that same home can use a lot less electricity if some attention is paid to installing energy efficient appliances, integrating smart home devices that can switch off appliances when nobody’s home, using landscaping to reduce the seasonal heating and cooling effects of weather, killing vampire loads (power consumption by appliances and devices on standby), and insulating and shading the home. That’s why, when considering going solar, it’s well worth reducing your electrical demand first, rather than attempting to power a wasteful home with solar energy.

Insolation (the amount of incident solar radiation hitting a given area over a specific amount of time) will also come into play when figuring out how many solar panels you’ll need, as some areas of the country receive much less than others, due to both the geographic location itself and the local weather patterns. Regions with long periods of cloud cover can produce less solar power from the same size solar array than those with long periods of clear sunny weather.

Another variable that will affect how many solar panels you’ll need is the efficiency of the solar panels themselves. It’s entirely possible to get cut-rate solar panels and save a few bucks on the front end, but end up with a less efficient system that will generate less electricity over the long run. Although we often see new records in solar cell (the building blocks of solar panels) efficiency being made by prototypes and R&D efforts, the most commonly installed solar panels are not nearly as efficient, and therefore more panels are needed to generate the same amount of energy.

Along with solar panel efficiency, the angle of the proposed rooftop location for the solar array will affect the performance of the system, as will the orientation of the available rooftop area, as the sun moves through the sky during the day and the angle of the sun changes over the season. Trees or other buildings that may cast shade on the array during certain times of the day or the year will also reduce the effectiveness of the home solar system, but getting a free solar site evaluation will help to identify which, if any, of these will affect a solar array on your roof.

Well, we still haven’t given you a concrete answer to your question of “How many solar panels do I need?”, but we hope you’re closer to understanding why there is no one answer to that.

Far better questions to ask are something along the lines of:

“How many solar panels do I need to power my whole house, with these specific loads and during these specific times of the day?”

“How many solar panels do I need to offset most of my electricity use in this specific state or region, with this average monthly consumption of electricity?”

“How many solar panels do I need for my location, with this average electricity consumption, in order to meet 50% of my home’s power needs over the course of a year?”

To find out how many solar panels you need for your specific situation, get a free solar report on your property!