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REopt Lite Tutorial: Advanced Utility Rate Input (Text Version)

This is a text version of the video REopt Lite Tutorial: Advanced Utility Rate Input.

Under the Site and Utility section of REopt Lite®, we can customize values to best fit our desired outcomes. Review the Overview module for guidance on the required fields in this section (which are marked by asterisks), or follow along to enter more specific, optional information.

If you choose to enter a net metering system size limit, you can do so in the available box. The default, a net metering system size limit of 0 kilowatts (kW), indicates that net metering is not available at the site.

You can also add a wholesale rate for electricity exports exceeding net metering or for sites where net metering is not available. For more information about how REopt Lite models net metering and wholesale rates, click on the blue tooltips next to the inputs and check out the user manual.

You may also choose to model a custom utility rate by checking the box next to “Use custom electricity rate,” and then toggling Annual, Monthly, or Detailed, based on the level of detail with which you’d like to model your site’s rate.

For the annual custom rate, you can enter a dollars/kilowatt-hour energy charge that will apply to all electricity purchases throughout the year. The dollars/kilowatt demand charge will apply to the monthly peak demand each month of the year.

Similarly, for the monthly custom rate, you can enter the dollars/kilowatt-hour energy charge and the dollars/kilowatt demand charge that will apply each month, but can vary throughout the year.

For a detailed custom rate, you must be logged in to REopt Lite, as custom rates are saved to your account. Note that custom rates should be developed before entering your other site inputs to avoid losing your progress.

To start building a detailed custom utility rate, choose a name and, optionally, a description for the rate you’re developing. If you’d like, you can start with and then modify an existing [Utility Rate Database] URDB rate by checking “Edit an existing utility’s rate,” entering the existing rate’s location (this does not need to be the same location as your site), selecting the electricity rate from the dropdown, and clicking “Populate form with existing rate.” You can then view and modify the energy charges and demand charges as desired.

For our purposes, let’s start with the default custom rate.

The energy and demand charge structures can incorporate time-of-use and tiered rate components.

First, we’ll look at the time-of-use component of energy charges. The Weekday Schedule shows a table of months and hours, and identifies the Period in which each weekday month-hour falls. For example, in January through April and October through December, electricity purchases cost a flat dollars/kilowatt-hour rate throughout all hours of the day, indicated by Period 2.

Looking at the corresponding table of charges, we see that electricity costs $0.08/kWh during all hours of Period 2. However, in May through September, the cost of electricity increases during the hours of 10 a.m. through 7 p.m. Note that the hour listed in the schedule indicates the hour starting at that time, so the last hour of this increased electricity charge starts at 6 p.m. and ends at 7 p.m.

Now let’s see what electricity costs during this midday period during the summer months. Looking at the table summarizing rates, we see there are two tiers in Period 1. The first 100 kWh each month will be charged at the Period 1, Tier 1 rate of $0.10/kWh. Any electricity purchased during these hours, beyond 100 kWh, will be charged the Period 1, Tier 2 rate of $0.12/kWh.

You can modify the energy charges and maximum energy purchases for each period and tier in the table summarizing “Energy Charges – Rate Periods.” You can also add tiers, add rate periods, and delete tiers and rate periods.

To change the time-of-use periods on the schedule, highlight a range of month-hours, select the desired period from the dropdown list, and “Add to Schedule.”

If you scroll a bit, you’ll see there is also a Weekend Schedule for energy charges. The periods listed in this table correspond to the same table of “Energy Charges – Rate Periods” that we’ve been working from, and work the same way. This table allows for a different rate schedule on weekdays and weekends.

If we continue scrolling, we’ll see a very similar table for the Demand Charges schedule. Like energy charges, demand charges can also include time-of-use and tiered structures.

Time-of-use demand charges are applied to the peak monthly demand that occurs during the defined set of hours that month. As modeled in the defaults, the monthly demand charge varies by month but does not depend on the timing of the peak.

Let’s look at adding a time-of-use demand charge to the hours of 8 a.m. through 6 p.m. for the months of May through September. During this period, let’s set the time-of-use demand charge to $18/kW. In this situation, Period 1’s demand charge—$15/kW—would apply to the peak demand that occurs between 6 p.m. and 8 a.m. each month of the summer. Period 3’s demand charge—$18/kW—would apply to the peak demand that occurs between the midday hours of 8 a.m. to 6 p.m. during each month of the summer.

If your site has a tiered demand rate, you can add tiers to the “Demand Charges – Rate Periods” table. What we’ve done here is set a Period 2, Tier 1 maximum demand of 100 kW. The first 100 kW of peak demand will be charged at $12/kW, and any additional kilowatts of peak demand exceeding 100 kW will be charged at $10/kW. So, if the peak demand for a winter month was 150 kW, that month’s demand charge would be 100 kW multiplied by $12/kWt—plus 50 kW multiplied by $10/kW.

As with the energy charges, demand charges can have a different weekend schedule than the weekday schedule.

Once you’ve finished setting up your custom rate, click “Create New Custom Rate.” This saves the rate to your Custom Rate database.

Now, if we go to the REopt Lite evaluation page, we can select our custom rate from the dropdown list and proceed with our analysis.