Accurately. With solar, size really does matter!Some solar companies may deliberately undersize your solar system because they think that homeowners will only focus on the monthly solar payment and not the overall savings. This, however, can leave you buying expensive utility power that is subject to price fluctuations. Likewise, oversizing your system is also problematic because you are paying for solar panels that produce power that you are not using.
The best approach is to consider all the factors that impact the solar system’s size and design a custom solution that maximizes your return.
Factors that influence solar system sizes include:
- How much energy your family uses
- Any planned increases in energy usage (pool, jacuzzi, electric car etc.)
- The physical characteristics of your property including available roof or ground space and shade from trees or other obstacles
- The prevailing sunlight in your area (including zip code specific micro-climates)
- Whether your utility has tiered electricity rates
How much power am I currently using?
If you don’t know how much power you usually use, don’t feel bad. Most people don’t. But knowing how many kilowatt hours you use is a vital first step to getting the correct solar system size for you.
The best way to figure this out is to pull the last 12 months of your electric bills and get an average. If you don’t keep that paperwork, you can usually access it on your utility company’s website, or call them directly. We can help you get that information so that we can use it as the basis of our calculations.
Power consumption tends to vary a lot by state. In 2012, the average annual electricity consumption for a U.S. residential utility customer was 10,837 kilowatt hours, or 903 kilowatt hours per month. Louisiana had the highest annual consumption at 15,046 kWh and Maine the lowest at 6,367 kWh.
Power usage also varies based on the season. For instance, during the winter months my home’s monthlyaverage is 1,100 kilowatt hours, mostly thanks to the furnace kicking on. During the summer, it’s much lower (because we don’t use air conditioning) and drops to around 430 kilowatt hours.
Our energy consultants take into account these regional and seasonal fluctuations and size your solar system based on a 12 month average. Additionally, we know that solar systems produce more power in the summer because the sun is at a higher angle in the sky, and the solar panels will receive more sun exposure compared to the winter months.
So because your usage varies, and the output of the solar system changes with the seasons, there will be months where the system will be producing more power than your house consumes, and months where you use more power than the system produces.
The good news is that most utilities allow for net metering. Net metering is a key driver of the current boom we are seeing in the solar industry. It allows for you to defer making a utility payment for 12 months, and then paying the utility for only the net power that you used. In other words, you are able to over-produce in some months, and under-produce in other months, and just make one payment at the end of the year for the net power that you used. Our job is to design a system that minimizes your annual payment without producing excess power.
What if I start using more power after my solar panels are installed?
Look, I’ll tell you that it’s human nature to be a little more liberal with your usage when you get a solar system. It’s difficult not to be. Although we do our best to accommodate any planned usage increases, we often see people leaving the lights on a little more, running the pool pumps a little longer, or setting the AC slightly lower. Of course that means that your utility bill will go up (since the solar output will not change). But hey, at least the solar is significantly offsetting your bill and, in some states, keeping you out of the more expensive tiers of electricity.
However you use it, solar power will benefit you and your family for decades. The key is making sure the solar system is sized to fit your needs.