Welcome to the Energy Efficiency Myths series from Direct Energy! As many myths arise from incomplete knowledge, they can create seemingly possible answers that many people accept as fact. Each month, we will examine common misunderstandings about energy efficiency — whether it’s in your home or about the energy industry — and deliver real facts behind the myth (and how they they might be costing you money).
How many solar panels do I need per square foot of my home?
For homeowners considering rooftop solar, there’s a lot of confusion over this notion that needs unpacking.
Technically, the number of panels per square foot of your home is irrelevant. The issue is purely how much energy you use. After all, you want a system that can meet your usage needs. A 1,500 square foot home doesn’t use any energy; it’s the people living inside that do.
That said, however, some utilities use the watts per square foot as a means to estimate for new home construction or retrofit. For example, a 1500 square foot home will likely use fewer lights than a 2500 square foot home. California uses 2.0 watts per square foot as a residential solar standard but that value won’t work in other states. To push this to the extreme, summer electricity usage for a 1,500 square foot home in Hatfield, MA is in no way comparable to a 1,500 sq ft. home in Palm Springs, CA or Houston, TX.
So, while panels/square footage provides a useful ballpark estimation when you begin thinking about how much power you’re likely to use, it’s really a bad metric to rely on for buying panels. You still have to sit down and add up how much electricity you expect to use and how much insolation your location receives.
Solar is still too expensive because you have to buy batteries.
You can have solar panels for your home and maintain a grid tie. Being able to rely on roof top solar reduces the amount of electricity you’ll need from your local utility but keeping a grid tie allows you to be supplied with electricity from your utility when your solar panels aren’t producing as much — such as rainy days or nights. Plus, 41 states have net metering policies that will allow you to sell any of your excess solar-generated power back to your local utility.
But doesn’t a grid tie mean that if there’s a blackout, your solar system’s anti-islanding inverter must shut down to prevent power crews from injury?
Yes, that’s true. However, grid-interactive inverters (the control box that changes solar panel DC power to household AC) allow homes with solar arrays to disconnect from the grid but continue supplying a limited amount electricity to the home.
Solar panels are ugly and will bring down the value of my home.
That aesthetic may have have been prevalent 20 years ago when solar panels with larger and heavier. Newer panels are thinner, sleekly designed, and are now seen as an enhancement to the value of your home. A study by Lawrence Berkeley National Laboratory found that home buyers were willing to pay $15,000 more for a house equipped with a mid-sized 3.6 kilowatt (KW) solar array versus a similar home without one. Another study published by the Appraisal Journal showed that the added amount of return from the solar arrays did not pay for them. If you install a solar array as a means to recoup the investment at sale, you’re not very likely to get that. However, the return was higher than the estimated income earned from their generating electricity.
Having solar means you have to give up air conditioning.
This myth makes several dated assumptions:
—That your solar panels don’t produce much electricity.
—That your home is not energy efficient.
—That your home’s air conditioning system is not energy efficient.
—That that you don’t have a grid tie.
The average residential solar array produces 5,000 watts (5kW) and consists of 25 200 watt panels. Larger arrays on larger roofs can produce more. Central air conditioning in an average home consumes 3,500 watts. From that rough comparison, it is possible to run your AC but there’s not a whole lot of power left over.
But, when you consider that homeowners who install rooftop solar are also more likely to improve their home’s energy efficiency, that begins to reduce how often the AC will be used. Add also that newer Energy Star home central air systems are 30% more efficient than those made 12 years ago, plus the fact that roof top solar arrays help reduce a home’s cooling load by shading the roof, then the discussion changes to “With all that energy efficiency, how often are you likely to need air conditioning?”
Still, there’s going to be hot summer weather. Keeping a grid tie ensures that you don’t have to give up air conditioning while having a solar array and being more energy efficient means you won’t pay as much.
Do you know of any Energy Efficiency Myths you’d like us to dispel? Share with us in the comments!