Step 4: Calculate Actual Savings

Calculate what the bill would have been without solar, account for tariff changes when needed, and compute actual savings.

Use the Calculation API to calculate what the customer’s bill cost would have been if they did not install solar. With this value, you can determine actual savings. Read Account Cost Calculation for more information.

Actual savings workflow

1. Use the actual bill cost calculated in Step 2.
2. Use the solar cost calculated in Step 3, if applicable.
3. Calculate the bill without solar by adding actual solar production back into the electricity load.
4. Include the pre-solar masterTariffId if the customer changed tariffs after installing solar.
5. Subtract the actual bill cost and solar cost from the bill without solar cost.

Calculate what the bill would have been without solar production

To calculate what the bill without solar would have been, back out the impact of solar production on the net electricity usage at the grid. Use this sample request for a billing period. You explicitly add the solar production back into the electricity load by adding a propertyInputs entry with the actual solar production profileId or providerProfileId and an operator of +.

POST /rest/v1/accounts/pid/actual-savings-example/calculate/

{
  "fromDateTime": "2015-07-20T00:00-0700",
  "toDateTime": "2015-08-19T00:00-0700",
  "billingPeriod": true,
  "minimums": false,
  "groupBy": "MONTH",
  "detailLevel": "CHARGE_TYPE",
  "propertyInputs": [
    {
      "keyName": "providerProfileId",
      "dataValue": "actual-savings-example-solar",
      "operator": "+"
    }
  ]
}

Calculate what the bill would have been with a tariff change

If you want to see the costs for a customer who switched tariffs when they installed solar, include the masterTariffId of the pre-solar tariff for the bill without solar. The calculation will then use the rates of the pre-solar tariff. Use this example:

POST /rest/v1/accounts/pid/actual-savings-example/calculate/

{
  "fromDateTime": "2015-07-20T00:00-0700",
  "toDateTime": "2015-08-19T00:00-0700",
  "masterTariffId": "{masterTariffId of pre-solar tariff}",
  "billingPeriod": true,
  "minimums": false,
  "groupBy": "MONTH",
  "detailLevel": "CHARGE_TYPE",
  "propertyInputs": [
    {
      "keyName": "providerProfileId",
      "dataValue": "actual-savings-example-solar",
      "operator": "+"
    }
  ]
}

In some rare cases, you might want to back out rate applicability changes to understand costs without the tariff change and without enrolling in a smart rate option. To do this, pass in additional propertyInputs with the rate applicability property values you want to use.

Calculate the actual savings

The final step is to calculate actual savings. Utility savings are found by subtracting the actual bill cost from the bill without solar cost. To get net savings, also subtract the actual solar cost.

For example, for the billing period of 7/20/2015 to 8/19/2015, there is an actual bill cost of -$61.79, a bill without solar cost of $199.61, and a solar cost of $185.44.

Actual savings is calculated as:

Bill without solar - Actual bill - Solar cost = Actual savings

For this billing period:

$199.61 - (-$61.79) - $185.44 = $75.96

Summary

You have calculated the bill without solar and used it with the actual bill cost and solar cost to calculate actual savings for the billing period.

Next steps

• Run an Account Cost Calculation to Match a Bill
• Calculation Details and Grouping