Savings Analysis API Support for Non-bypassable Charges


| Reading time 4 minutes

Genability has just upgraded both our Savings Analysis API and our Calculate API to better support Non-Bypassable Charges (NBCs). What are NBCs you ask? Well that’s how the California utilities refer to the customer’s annual NBCs that cannot be offset by Net Energy Metering (NEM) Credits under NEM 2.0. These NBCs behave as a second minimum charge calculation that’s performed during the customer’s annual true-up.

Confused? We’ll try to make all the possible cost calculations for solar customers under NEM 2.0 comprehensible and explain how we represent these costs in our calculations.

NEM 2.0 and Non-bypassable Charges (NBCs)

Under NEM 2.0, California utilities do not provide solar customers with credit for energy exported to the grid for these four rates:

  • DWR Bond Charge
  • Public Purposes Program Charge
  • Ongoing Competition Transition Charge
  • Nuclear Decommissioning Charge

So while NEM 2.0 customers do receive net metering credits whenever they produce more power than they consume within a month, they will receive no credit for the Non-Bypassable portion (roughly 2¢/kWh as of 1/1/2019) of their charges. These NBCs cannot be offset in any way. If the customer’s NBCs are greater than the minimum charges, the NBCs constitute a second, higher minimum charge.

California Utility Bills for Solar Customers

When you install solar on your home in Pacific Gas & Electric (PG&E), Southern California Edison (SCE) and SDG&E (San Diego Gas & Electric) territories, the utility switches you from monthly to annual billing. The utility bills solar customers for the minimum costs for the first 11 months and performs an annual true up in the 12th month (see next section). This allows solar customers to use NEM credits generated in the Spring and Summer to offset charges in the Fall and Winter.

The Annual True-Up Calculation

At the end of the year, the utility performs multiple calculations of the solar customer’s costs, and chooses the highest value. Here’s a summary of the cost calculations involved (click here to read the full description):

  1. Total Minimum Delivery Charges - 12 monthly delivery minimum charges (~$120) plus positive supply charges (calculated annually)
  2. Total Non-Bypassable Charges - The annual cost of the NBCs
  3. Total Solar Net Usage Charges - The annual cost of the customers electricity charges including NEM credits.

What has Changed

Genability has always performed calculations numbers 1 and 3 from the list above. We have now added support for 2. Minimum Non-Bypassable Charges. This appears in three places in our API:

Tariff API

NBCs are now identifiable in the Tariff Response according to ChargeClass. Here’s an example:

GET /rest/public/tariffs?masterTariffId=3250148&effectiveOn=2018-12-01&populateRates=true  
"tariffRateId": 18187838,
"tariffId": 3316562,
"tariffSequenceNumber": 36,
"rateGroupName": "Delivery Charge",
"rateName": "DWR Bond Charge",
"fromDateTime": "2018-10-01T00:00:00-07:00",
"toDateTime": null,
"chargeType": "CONSUMPTION_BASED",

"chargePeriod": "HOURLY",
"applicabilityKey": "hasMedicalBaselineExemption",
"rateBands": [
"tariffRateBandId": 12065455,
"tariffRateId": 18187838,
"rateSequenceNumber": 1,
"hasConsumptionLimit": false,
"hasDemandLimit": false,
"hasPropertyLimit": false,
"applicabilityValue": "false",
"rateAmount": 0.00549,
"rateUnit": "COST_PER_UNIT",
"isCredit": false,
"prevUpperLimit": null


Calculate API

An additional line item can be added to the calculation that isolates the NBC charges. The API will return the non-bypassable charges in the calculation summary.

"summary": {
"kWh": 0,
"kW": 0
“nonBypassableCost”: 16.82,
"subTotalCost": 33.96,
"taxCost": 0,
"totalCost": 33.96,
"adjustedTotalCost": 33.96,
"kWh": 0,
"kW": 0

The Non-Bypassable charges returned will not impact the calculation totals, but are provided separately to make it easy for you display to your customers.

Savings Analysis API

When determining the annual cost post-solar, NBC charges will be evaluated along with Delivery Minimum and Net Solar Costs. If it is the highest calculated value it will become the first year postTotalCost in the results summary section. It will also appear in the summary section for your reference under the parameter name: postTotalNonBypassableCharges:

"lifeTimeUtilityAfterCost": 8927.848,
"lifeTimeUtilityAvoidedRate": 0.352,
"lifetimeAvoidedCost": 18367.917,
"lifetimeSolarCost": 20284.165,
"lifetimeWithoutCost": 47579.93,
"netAvoidedCost": 1559.1,
"netAvoidedCostPctOffset": 0.9267,
"netAvoidedKWh": 6315.33,
"netAvoidedKWhPctOffset": 0.7518,
"netAvoidedRate": 0.246875,
"postTotalCost": 138.84,
"postTotalKWh": 2084.667267,
"postTotalKWhCost": -70.833766,
"postTotalKWhRate": 0.246875,
"postTotalMinCost": 123.37,
"postTotalNonBypassableCost": 138.84,
"postTotalNonMinCost": 87.437233,
"postTotalRate": 0.05918,
"preTotalCost": 1682.47,
"preTotalKWh": 8400.000001,
"preTotalKWhCost": 1743.159868,
"preTotalKWhRate": 0.20752,
"preTotalMinCost": 834.850001,
"preTotalNonBypassableCost": 164.84,
"preTotalNonMinCost": 1682.474868,
"preTotalRate": 0.200295

In the annual savings series, we will project future post-solar costs by escalating three scenarios (delivery minimums, net solar costs and NBCs), selecting the highest cost for each subsequent year in the lifetime of the solar system.

Updates to the Switch UI

We have added a visual indicator in the Switch Dash whenever the minimum Non-Bypassable Charges are the After Solar Total Cost. You can see the new NON-BYPASSABLE badge in the in the monthly cost histogram, the summary of monthly savings and the detailed view of monthly savings. You can see the first two in the screenshot below.

Impact on Solar Savings in California

The inclusion of NBCs in the calculation of post-solar utility costs, makes a small but demonstrable difference for solar systems that produce more than 6,000 kWh annually. How much impact depends on both the size of the solar system and how much of the customer’s electric load is offset by the solar system. Large solar systems and higher solar offsets increase the impact of NBC minimums on customer savings. Here’s a few representative avoided cost of power (ACP) differences assuming 100% solar offset:

Usage (kWh/yr) Solar Exported Min. Charge NBC Charge ACP without NBCs ACP with NBCs
6,000 3,600 $120 $69 $0.202 $0.202
12,000 7,200 $120 $138 $0.252 $0.250
18,000 10,800 $120 $207 $0.273 $0.268
24,000 14,400 $120 $276 $0.300 $0.293

This is just another example of how Genability continues to extend our calculation engine as utilities introduce new ways of charging customers for power.

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