How to Audit Your Manufactured Housing Utility Billing

Rate changes happen. Billing providers make errors. California's rules are specific. Yet many manufactured housing operators have no way to independently verify that their utility billing is accurate and follows California law.

An audit does not require legal expertise — it requires methodical comparison of what appears on resident bills against what should appear based on the serving utility's published tariffs and the requirements of the Mobilehome Residency Law. This guide walks through the process step by step.

For background on the statutory requirements referenced throughout this guide, see the complete compliance guide and the California rules guide.

Step 1 — Obtain Your Current Rate Schedules

The foundation of a billing audit is the published tariff. Every utility rate on every resident bill should trace back to a specific rate schedule published by the serving utility. Your first step is to obtain the current versions of every rate schedule that applies to your property.

Where to Find Tariff Documents

Major California utilities publish their tariff schedules online:

• Southern California Edison (SCE): Tariff books are published on SCE's regulatory information page. Residents are priced on the residential schedule a directly served home is on — Schedule D. The community's own master-meter schedule, DMS-2, sets what the community pays SCE, never the resident's rate.
• Pacific Gas & Electric (PG&E): Tariff schedules are available through PG&E's electric and gas tariff pages. Residents are priced on the residential schedule a directly served home is on, such as E-1; the community's master-meter schedule (ET or ETL) sets what the community pays.
• Southern California Gas (SoCalGas): Gas tariff schedules are published on SoCalGas's regulatory page. Residents are priced on Schedule GR (general residential service), the schedule a directly served home is on.
• Water purveyors: Water and sewer rates are published by each serving water district or company (e.g., Eastern Municipal Water District; Cal Water, a CPUC-regulated water company). These are typically available on the purveyor's website or by request. They set what the community pays; residents are billed, where water is submetered, from the community's own water bill by a § 798.40(c) method.

What to Look For

For each utility type billed at your property, identify:

• The specific rate schedule name and number (e.g., SCE Schedule D)
• The effective date of the current rate schedule
• The per-unit rates for each tier, if tiered pricing applies
• The base or service charge (daily or monthly)
• Baseline allocation quantities, if applicable
• Seasonal rate variations, if any
• The CARE and FERA discount percentages for that schedule

Step 2 — Compare Rates on Bills to Published Tariffs

With your current rate schedules in hand, pull a sample of recent resident bills and compare the rates applied on each bill against the published tariff. For gas and electricity from an investor-owned utility (including community-choice electricity) this is the rate parity check required by Cal. Pub. Util. Code § 739.5(a). Water is different: check that it is billed by one of the Cal. Civ. Code § 798.40(c) methods from the community's own water bill (or, under § 798.40(c)(1)(B), its tier rates applied to evenly divided tier volumes) — not by the purveyor's posted residential rates, unless the purveyor charges the community per space.

How to Read a Tariff Document

Tariff documents can be dense, but the relevant information follows a consistent structure. Look for:

• Effective date: The date the rates in this schedule took effect. This determines which rates should be on bills for a given billing period.
• Energy charges: The per-unit rates (per kWh for electric, per therm for gas, per CCF or HCF for water). These may be organized by tier.
• Base/service charge: A fixed charge per day or per month, independent of consumption. Note whether this is a daily rate (which must be multiplied by the number of days in the billing period) or a flat monthly charge.
• Tier boundaries: The consumption thresholds where the per-unit rate changes. Baseline quantities may vary by climate zone, season, and whether the space is all-electric.

Common Discrepancies

Common discrepancies found during rate audits:

• Outdated rates: The utility published new rates months ago but the billing system still uses the old rates. This is a common error — and it goes in both directions. If the new rate is higher, the operator is under-collecting. If the new rate is lower, every bill since the effective date has overcharged residents.
• Wrong rate schedule: The billing system applies a different schedule than the one that actually applies to the property's service classification. This can happen when properties change service classifications or when a billing provider makes an incorrect initial setup.
• Wrong base charge type: Confusing a daily base charge with a monthly one — or failing to multiply a daily charge by the correct number of days — produces a systematic error on every bill.
• Rounding errors: Tariff rates are published to multiple decimal places. Rounding to two decimal places before multiplying by consumption can produce errors that accumulate across a property.

Step 3 — Verify Tier Calculations

Many California utility tariffs use tiered or baseline pricing. Under a tiered schedule, use up to a threshold set by the home's baseline allowance is billed at one price and use above it at a higher price. The large utilities' tiered residential schedules now have two prices. If your property's billing uses tiered rates, verifying that tiers are applied correctly is essential.

How Tiered Rates Work

An example from a filed schedule — SCE Schedule D, bundled service, effective October 1, 2026 (Sheet 91558-E, Advice 5897-E):

• Up to baseline: $0.31384 per kWh
• Above baseline: $0.40485 per kWh

These prices combine delivery, generation and the Fixed Recovery Charge. A Region 10 all-electric home in winter gets 15.2 kWh a day of baseline (Preliminary Statement Part H, Sheet 91544-E), or 456.0 kWh over 30 days. At 487 kWh, the energy charge is 456.0 kWh × $0.31384 = $143.11, plus 31.0 kWh × $0.40485 = $12.55, for $155.66. Pricing all 487 kWh at the higher price would give $197.16 — $41.50 too much. The schedule also has a daily Base Services Charge ($0.794 per day), which is billed in addition to the energy charge.

Baseline Allocations

The tier boundaries are typically based on baseline allocation quantities set by the CPUC. Baseline quantities vary by:

• Climate zone: California is divided into climate zones that determine baseline quantities. A property in a hot inland zone receives a higher summer baseline than a property in a coastal zone.
• Season: Summer and winter baseline quantities differ.
• Heating source: All-electric spaces (permanently installed electric space heating; the exact test varies by utility) receive a higher electric baseline to account for electric heating.

To verify tier calculations, you need to know which baseline allocation applies to your property. This information is in the utility's tariff schedule and is determined by your service address.

What to Check

• Is the correct baseline quantity being used for your climate zone and season?
• Is consumption correctly split between tiers at the right boundary?
• Are all-electric spaces receiving the higher all-electric baseline allocation?
• Are seasonal rate changes being applied on the correct dates (summer and winter rates typically have different effective dates)?

Step 4 — Check CARE/FERA Discount Accuracy

If any residents at your property are enrolled in CARE or FERA, verify that the correct discounts are being applied.

What to Verify

• Does each enrolled resident's bill show the CARE discount as an itemized amount or a CARE notation, and the FERA discount the utility's schedule provides?
• Is the discount percentage applied the same as the utility's current published CARE or FERA discount for your rate schedule?
• Is the discount calculated on the base the utility's CARE or FERA schedule names — generally the whole bill less the charges the schedule exempts?
• Is the correct program applied — CARE for CARE-enrolled, FERA for FERA-enrolled?
• Are there any enrolled residents who are not receiving a discount?

CARE passthrough is required by Cal. Civ. Code § 798.43.1(c); FERA reaches a submetered resident through Cal. Pub. Util. Code § 739.5(a) (SCE's master-meter schedule DMS-2 names Schedule D-FERA expressly). A household receives CARE or FERA, never both. For a comprehensive treatment of CARE and FERA obligations, including the annual notice requirement and privacy considerations, see our CARE and FERA passthrough guide.

Step 5 — Assess Compliance with MRL Requirements

Beyond rate accuracy, California law imposes specific requirements on the format and content of utility bills. Pull a sample bill and verify each of the following:

• Meter readings shown: Does the bill display opening and closing meter readings, and their dates, for each utility? (Cal. Civ. Code § 798.40(a); Cal. Pub. Util. Code § 739.5(e); Cal. Code Regs., tit. 4, § 4090)
• Separate itemization: Are utility charges separately stated from rent, and is each utility type itemized individually? (Cal. Civ. Code § 798.41(d))
• Rate parity: Do gas and electric rates match the serving utility's current published tariff, tier by tier, and is water billed by a § 798.40(c) method? (Cal. Pub. Util. Code § 739.5(a); Cal. Civ. Code § 798.40(c))
• Billing agent disclosure: If a third party prepares the billing, does every bill show its name, address, and telephone number? (Cal. Civ. Code § 798.40(b))
• Common area metering: If a meter on a resident's site also measures common-area service, was it disclosed and then cured — a written compensation agreement, or the load moved off that meter? (Cal. Civ. Code § 798.43)
• CARE/FERA passthrough: Are enrolled residents receiving the full discount the utility's schedule provides, shown as an itemized amount or a CARE notation? (Cal. Civ. Code § 798.43.1(c); Cal. Pub. Util. Code § 739.5(a))

For the full rule-by-rule analysis, see California Rules for Manufactured Housing Utility Bills. For a visual overview of how these rules are validated, see the compliance framework.

Step 6 — Document Your Findings

Whether your audit reveals issues or confirms compliance, documenting the process and findings is essential.

Why Documentation Matters

In a billing dispute, a record showing how each charge was calculated usually ends it early. A documented audit provides contemporaneous evidence that the operator reviewed its billing, verified rate accuracy, and confirmed statutory compliance.

What to Keep

• Copies of every rate schedule used, with the source tariff document and effective date
• Records of the comparison between billed rates and published tariff rates
• Documentation of CARE/FERA enrollment status and discount application
• Any discrepancies found and corrective actions taken
• The date the audit was performed and the billing periods reviewed

How Long to Retain Records

A state weights-and-measures regulation — not a CPUC rule — requires the rate schedules and individual billings to be kept for at least 12 months, open to the resident and the county sealer, and each billing period's invoice to show the opening and closing readings and their dates (Cal. Code Regs., tit. 4, § 4090). Sentinel keeps records for seven years; that is our practice, not law.

The Challenge of Doing This Yourself

The audit process described above is straightforward in concept but demanding in practice. The challenge is not that any single step is difficult — it is that every step must be done correctly, for every utility type, for every billing period, on an ongoing basis.

Rate schedules change. California utilities publish new rates periodically — sometimes annually, sometimes more frequently. Each rate change requires the operator to obtain the new tariff, identify the applicable rates, update billing accordingly, and document the change. Missing a rate change means every subsequent bill is priced wrong until the error is caught.

Tariff documents are complex. A single utility's tariff book may contain dozens of schedules, each with its own tier structure, baseline allocations, seasonal variations, and service charges. Identifying the correct schedule and extracting the applicable rates requires familiarity with tariff structure and terminology.

The work is continuous. A billing audit is not a one-time event. Rate accuracy and compliance must be verified on an ongoing basis — after every rate change, at minimum. For operators managing multiple properties with different serving utilities, the volume of tariff monitoring and rate verification compounds significantly.

Errors are costly to unwind. Getting it right produces no visible benefit — billing is simply correct. Getting it wrong means resident overcharges that must be corrected and refunded, revenue lost to under-billing, or a lawsuit under the Mobilehome Residency Law, where the winning side recovers attorney's fees (Cal. Civ. Code § 798.85).

For operators who want certainty that their billing is accurate without doing this work themselves, that is the problem that automated rate monitoring and bill checking are designed to solve.