sunMAX - Pre-Sale: Electricity Bill Analysis

Note: For a limited time, Ubiquiti is offering free consultation services. Send your customer Electricity Bills (12 months for accuracy) to sunmaxconsult@ubnt.com.

Overview

Knowing how to read Electricity Bills is fundamentally important to designing a system that meets your customer's needs.

When working in a particular city or state, you should be aware of the average Cost/kWh that residential customers face. Knowledge of Utility rates and structures is also vital as you communicate to your customers their return-on-investment in the long-term (25+ years).

In general, your objective in simulating your customer's arrays in the sunMAX design tool should be to offset the annual consumption (based on 12-months of electricity bills). The average US customer consumes approximately 11MWh/year (11,000kWh/year). 

Utility Tariffs (Rates)

The charges and rates at which customers are billed for grid-electricity usage are called Utility TariffsUtility Tariffs vary from company to company, but in general, are categorized into three groups:

  1. Customer Type - whether Residential, Commercial, Industrial
  2. Demand Levels - including Duty Cycles and Cost to Operate. Typically, these charges represent power levels, and are measured in kW. To compensate for the utility’s investment in the necessary/capable infrastructure, demand charges may be higher for peak power users.
  3. Rate Schedules - Tiered Usage Levels or Seasonal Rates, such as those shown in the diagram to the right.

Example 1 - Non-Solar Customer

 

Here is a Standard Electricity Bill, which presents in straightforward terms, the Total Energy Consumption for a given period.

  • In the Billing Details section, under Supply Services, the current Customer Rate Plan is listed. Based on the Winter Residential rate, the cost per kWh drawn from the grid is about 27¢.
  • The Service Period for this particular bill covers 30 days, from November 1st to the 30th.
  • For a Standard Meter, the customer is charged according to the kWh difference between the previous, and current meter reading. The total Supply Cost is then calculated by multiplying this figure by the Winter Residential energy rate.
  • The Basic Charge under Delivery Services is a flat fee relating to the customer’s connection to the Grid, and may account for overhead and maintenance costs.
  • Together, the Delivery & Supply charges equal the total bill amount for the payment period.
  • The information shown in the Electricity Overview section is particularly important to potential solar customers and integrators alike. Here, each bar measures the customer’s daily average kWh consumption by month.
  • The data collected over a 12-month range usually is sufficient to determine the required capacity of the solar energy system.
  • Too small of a system and production will not offset consumption; too large, and the customer risks a decreased return on investment.

Example 2 - Solar Customer (Net-Metered)

Now that we’ve examined the Standard Meter bill, let’s examine a sample Net Metering bill and instead, assume that the customer installed a Solar Energy system toward the end of January of 2015.

  • The Electricity Overview section now shows daily net energy levels by month.
  • Compared to the previous year, total consumption is much lower, since production offsets the grid-energy requirement.
  • By October, total energy production begins to exceed consumption enough to maintain a net positive in stored energy credits over the lifetime of the customer’s solar energy system.
  • Back on the billing section, under Supply Services, these credits have already accrued in the customer’s account.
  • Since a production surplus occurred again for the current billing cycle, the credit total again increases, with net consumption for the November at zero.
  • Some Delivery Service charges may still apply—including Interconnection Agreement costs.
  • However, in this Net-Metering case, where energy is bought-back at a 1:1 ratio, the Solar Energy System is shown to reduce the customer’s total electricity bill by 95%+.