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Gaining a baseline understanding of the many types of electricity rates and bill charges is an important first step in determining whether a different Georgia Power rate plan can lower your utility costs. But how do these calculations shake out in a real-world scenario? 

 

Perhaps you have a general sense of your monthly electricity use and how things like your HVAC system or your electric vehicle charger impact your usage. You might know that you use more electricity in summer than winter. Likely, though, you don’t know what your peak electricity demand was last month or last summer, exactly what you did to set that peak demand, or how much of your monthly use occurs at a particular time of day. Your utility company knows and may already charge you accordingly, so it benefits you to be just as knowledgeable about your usage patterns.  

 

Let’s delve into three key facts with my family’s own usage data as an example: 

  1. Your electricity use varies by season 
  2. Your electricity use varies across the hours of the day 
  3. Your electricity use peaks at certain times (and your utility plans its system partly on this fact) 

Seasonal Variance 

In the figure below, the red bars highlight that my family’s electricity use peaks during the summer months. Since we live in Georgia, the reasons may be obvious—my family has an electric central AC unit that uses a lot of electricity to cool our old, leaky house in the hot summer months. We also use a natural gas furnace to heat our home in the winter, so that increase shows up on our natural gas bill instead. Our HVAC is the main driver of seasonal variance in our electricity use. The electricity we use for things like lighting, refrigeration, appliances, and plug loads don’t vary much seasonally (except for the space heater whirring away under my wife’s desk when it’s cold outside).  

 

This graph would look different if we heated our home with an electric heat pump (likely showing both summer and winter peaks with lower use in fall and spring months). It might even look different if my house had insulation in the walls and floor (showing less distinct summer peaks).  

My Monthly Electricity Use: Jan 2019 – Dec 2022 (kWh)

Hourly Variance 

Now, let’s look at my hourly electricity use for a day in late June 2022. Just as my monthly use varies across the seasons of the year, my use varies across the hours of the day. On this day, our use spiked slightly as we turned on the coffee maker and cooked morning oatmeal on the stove. But the real shift came as the afternoon heat rose, and our AC unit worked to keep our house cool. I’m not sure what happened at 11 pm, but I suspect it has something to do with teenagers. 

My Hourly Electricity Use for a Day in Late June 2022 (kWh)

Customer Peak Demand 

The next figure shows my hourly electricity use for 12 months displayed in what is typically called a load duration curve – this technique arrays each hour of use (kW) from highest to lowest. This highlights some key features of my family’s electricity use. Across most hours of the year, our hourly electricity use ranges from 0.5 kW to 1.5 kW, but in a few hours of the year, my electricity use exceeds that by a lot, reaching a peak of 7 kW in a single hour. We likely reach those hours of peak electricity use when our AC unit is running with additional use from our electric stove or clothes dryer “stacked” on top. 

 

Hourly Load Duration Curve for My Home for 8,760 Hours (Feb 2022 – Jan 2023)

Next Up: Using Data to Decide  

Armed with an understanding of different electric bill charges and how utilities set their rates to reflect usage patterns, we’ll return to the central question of this blog series next: Can I save money by switching to another of Georgia Power’s residential electric rate plans?  

 

Georgia Power offers a broad range of residential rate structures, including a tiered rate and three time-of-use rates, one of which includes a demand charge. I began my personal case study with Georgia Power’s Standard Residential (R) rate, a tiered rate structure. Does my family’s usage data suggest that this rate is the best option for us or should we change? 

 


Kevin Kelly

Electric Bills Decoded is Southface Institute’s series exploring how Georgia Power residential customers can use data to help determine whether changing their electricity rate plan can lower their utility bills and offset recent rate hikes. Follow along to understand different types of rates and charges; identify electricity usage patterns; use your data strategically; consider the impact of going solar; explore several case studies; and learn about battery storage as a cost-saving tool. We’re decoding it all! 

 

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