# Utility Split Estimation > Estimate the landlord/tenant (owner/tenant) utility-cost split for an asset — per fuel (electricity, gas, water) — so the landlord share can be used as the SAVINGS BASIS for retrofit economics. This gates every retrofit IRR: savings only accrue to whoever pays the bill, so the split must be estimated properly from evidence, never defaulted to 100%-owner or a round number. Combines building form, jurisdiction pass-through (RUBS) rules, the asset's OWN documents (leases, OMs, PCAs, audits), and live leasing evidence (apartments.com etc.), then records the estimate as an adjudicable verifier finding. Extensible by asset type — multifamily is shipped; office/retail/industrial are stubbed with their determining factors. Triggers on: "utility split", "landlord/tenant split", "owner/tenant utility split", "landlord share", "who pays the utilities", "utility responsibility", "RUBS", "utility recovery", "utilities included", "tenant pays electric", "savings basis", "master metered vs individually metered". - Skill: `soapboxbuild/utility-split-estimation` (Agent Skill, multi-file: 5 files) - Install (CLI): `npx skillmds@latest add soapboxbuild/utility-split-estimation` - Raw SKILL.md: https://api.skillmd.com/api/skills/soapboxbuild/utility-split-estimation/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: soapboxbuild (https://skillmd.com/u/soapboxbuild) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/soapboxbuild/utility-split-estimation --- # Utility-Split Estimation Estimate what fraction of each utility (electricity, gas, water) is paid by the **landlord (owner)** versus the **tenant (resident)** for one asset. Produce a per-fuel split with the evidence for each, labeled **PRESUMED** vs **CONFIRMED**, a confidence note, and the single question to ask the owner to confirm. Record the estimate as a verifier finding so it is adjudicable, and — when Audette is in play — flag that Audette's landlord-share settings must be updated to match the confirmed split. ## Why this matters (do not skip, do not default) Retrofit savings accrue **only to the party that pays the bill**. If residents pay 90% of the electric load, an electric-efficiency measure returns ~10% of its dollar savings to the owner — and its IRR collapses accordingly. The landlord share is therefore the **savings basis** for every measure's economics. A wrong or defaulted split silently mis-prices the entire measure plan. **Never assume 100%-owner, never assume a round number, never carry a prior asset's split forward.** Estimate it from this asset's evidence. This is frequent, load-bearing work: it feeds `decarb-plan` P3 economics and any retrofit IRR. Run it whenever an asset's owner/tenant utility split is unknown, stale, or unconfirmed. ## Core method (all asset types) Work these four evidence sources **in order**, stopping to record what each yields. Sources lower in the list refine or confirm what higher sources presumed; a document or a bill that states responsibility outranks an inference from building form. 1. **SEARCH THE ASSET'S OWN DOCUMENTS FIRST.** Before any inference or web search, look in the asset's uploaded files — leases and lease abstracts, the Offering Memorandum (OM), PCAs, energy/water audits, operating statements (T-12), and utility bills frequently state utility responsibility outright ("resident pays electricity", "owner pays gas heating and hot water", a RUBS line item, an expense-stop clause). Use `list_files` / `search_files` then `read_file` / `search_documents` with queries like *"utilities", "resident responsible", "tenant pays", "RUBS", "master metered", "individually metered", "expense stop", "recoveries"*. A document statement is the strongest evidence short of the owner confirming — mark those fuels **CONFIRMED** with the document cited. 2. **Building form** (asset-type-specific — see the module for this asset's type below). Metering configuration and central-plant layout set the *presumed* split when documents are silent. Example (multifamily): garden-style, individually-metered units → most electricity/gas billed directly to residents → **low landlord share**; mid/high-rise with central plants (central boiler/chiller, house-metered common systems) → **higher landlord share**. Building form yields a **PRESUMED** split, never a confirmed one. 3. **Jurisdiction pass-through / RUBS regulations.** Whether and how a landlord may bill utility costs back to residents is regulated locally (submetering rules, Ratio Utility Billing System allowances and caps, prohibitions on certain pass-throughs, tenant protections). This bounds what the split *can* be regardless of building form — a master-metered building in a RUBS-permitted jurisdiction may still pass most cost through; the same building where RUBS is barred leaves the cost with the owner. Search the reference library first, then web search; cite every rule with its source and URL. 4. **Live leasing evidence.** Pull the property's current listings/brochures (apartments.com, the property's own site, Zillow rentals, etc.) via web search. Listings routinely state "utilities included" or itemize "resident pays electric/gas/water" — this is real, current, market-facing evidence of what residents actually pay and often confirms or corrects the building-form presumption. Cite the listing and its URL. **Resolve per fuel, not per building.** Electricity, gas, and water frequently split differently (e.g. residents pay in-unit electric, owner pays central gas heat + common-area water). Estimate each fuel independently against the evidence above. ## Asset-type modules Read the module matching this asset's property type before finalizing the building-form step. Each lists the determining factors and how they map to a presumed split. | Asset type | Module | Status | | --- | --- | --- | | Multifamily | `asset-types/multifamily.md` | **shipped** — full method | | Office | `asset-types/office.md` | stub — determining factors listed | | Retail | `asset-types/retail.md` | stub — determining factors listed | | Industrial | `asset-types/industrial.md` | stub — determining factors listed | If the asset type has only a stub, use the listed determining factors plus the core method to produce a best estimate, mark the result **PRESUMED** with **low** confidence, and be explicit in the owner question that the split is unconfirmed. Do not fabricate precision the module does not yet support. ## Granularity rule (critical) ### Consumption allocation (when distributing whole-property utility data across building models) Never split evenly by default. Allocate in this order: (1) carve out identified common/amenity loads first (pool heater, clubhouse, exterior/corridor lighting — use the audit's end-use breakdown) and assign them to the building/line-item where they belong; (2) allocate the remainder across residential buildings weighted by GFA (adjust for known differences: floors, vintage, equipment); (3) state the allocation method with the upload. An even split is only acceptable when buildings are genuinely identical in GFA and use — and must still be labeled "GFA-weighted (identical buildings)". Apply the split at the FINEST granularity the model supports — per building and per end-use — never as one blended property-wide percentage. A blended % misattributes savings both ways: in-unit measures get phantom landlord credit, and fully-landlord amenity measures get under-credited. - Residential buildings with tenant-metered fuel: landlord share for that fuel = 0% in those building models. House-meter loads (corridor/exterior lighting, common HVAC) that live inside residential buildings keep a per-building landlord share for that fuel (typically electricity). - Amenity/clubhouse/pool buildings (no tenants): landlord share = 100% for their fuels. - **Master-metered ≠ 100% landlord.** A master-metered residential load is only ~100% owner if the owner ABSORBS it. If the jurisdiction permits RUBS, assume the owner rebills up to ~90% → net landlord share ≈ 10% for that load, unless documents show a true gross lease / no rebill. Never set a master-metered residential load to 100% by default. **The RUBS assumption is CONDITIONAL on the jurisdiction permitting RUBS — confirm it in step 3 (cite the statute); if RUBS is BARRED, the owner bears the cost (~100% on master-metered), not ~10%.** - **Solar under Virtual Net Metering (VNM):** assume 80% of solar output value flows to the landlord (owner-captured) — but **ONLY after confirming the state/utility actually offers VNM / aggregated NEM / community-solar export** (check the reference library → PUC/utility tariff → cite the rule + URL). **If only behind-the-meter (BTM) net metering is available (no virtual/export aggregation), solar value = BTM self-consumption offset only** — owner-share on the owner-paid loads it displaces — NOT the 80% VNM credit. Never assume VNM without the jurisdiction check. - If the model has NO separate amenity building (e.g. a property modeled as N identical residential buildings), set the tenant-metered fuel to 0% landlord across all modeled buildings and evaluate common-load measures (pool heater, clubhouse equipment) as standalone owner-paid line items outside the building models. Say explicitly which loads were handled this way. - Only fall back to a blended % when the modeling tool cannot express per-building shares — and label the blend and its composition. ## Output contract Produce, for the asset: **Per-fuel split table** — one row each for **electricity, gas, water**: | Fuel | Landlord share | Tenant share | Label | Evidence | | --- | --- | --- | --- | --- | | Electricity | e.g. 15% | 85% | PRESUMED / CONFIRMED | the specific document line / listing / building-form + jurisdiction basis, cited | | Gas | … | … | … | … | | Water | … | … | … | … | - **Landlord share** is the fraction of that fuel's annual **cost** the owner pays (this is the savings basis). If only a metering configuration is known and not a dollar split, state the presumed configuration and the share it implies, and mark it PRESUMED. - **Label each fuel** independently: **CONFIRMED** = a lease/OM/audit/bill or the owner states it; **PRESUMED** = inferred from building form, jurisdiction, or listings. - **Evidence** cites the exact source for that fuel (document + page/line, or listing URL, or the building-form + jurisdiction rule). No uncited splits. **Confidence note** — one short paragraph: how strong the overall evidence is, which fuels are weakest, and what would move a PRESUMED fuel to CONFIRMED. **The single question to ask the owner** — one precise, closed question that, once answered, confirms the presumed fuels. Example: *"For each of electricity, gas, and water — are these individually metered and billed directly to residents, master-metered and paid by ownership, or billed back via RUBS? If RUBS, what allocation formula?"* Tailor it to what is actually still open. ## Persist to asset metadata (the CANONICAL record — read this FIRST on every run) The resolved split MUST be written to a machine-readable field that survives across threads — otherwise every new session re-derives it and re-defaults to Audette's 100% landlord-share (the exact bug this skill exists to prevent). The verifier finding (below) is a QA/adjudication artifact and the register file is a human doc; **neither is read by the economics.** The canonical store is `metadata.utility_split`. - **WRITE** it via `update_asset_metadata(asset_id, { utility_split: {...} })` (an allowlisted key): ``` utility_split = { elec: , gas: <0-1>, water: <0-1>, // net owner capture per fuel source: "gig-cad | lease | listing | building-form | audette-default", confidence: "confirmed | presumed", basis: "", resolved_at: "" } ``` If the tool response reports a **REJECTED / not-in-allowlist** key, the split did NOT persist — STOP and surface it (the platform allowlist must include `utility_split`). - **READ it FIRST.** Before deriving a split — in this skill, in `portfolio-analysis`, and in `decarb-plan` — read `metadata.utility_split`; if present, USE it. Only run the four-source derivation when it is absent. **NEVER default to 100% owner, and never read the split from Audette's landlord-share, when a stored `utility_split` exists** (Audette re-defaults to 100% on model re-pull, which is why it can't be the source of truth). - **WRITE the split to BOTH stores on every run, where Audette is in play:** `metadata.utility_split` (the canonical Soapbox record) AND Audette's per-building landlord-share (section below). Audette's own engine applies its landlord-share to decide which measure savings accrue to the owner, so a split that lives only in metadata while Audette sits at its ~100% default produces overstated owner savings, IRRs, and value creation (the exact failure this skill exists to prevent). Keep the two in sync — `metadata.utility_split` is the authoritative human record — but **the split is NOT 'applied' until Audette reflects it.** (You still never *read* the source-of-truth split *from* Audette — it re-defaults to ~100% on re-pull — but you MUST *write* the confirmed split into Audette.) ## Record as a verifier finding (adjudicable) Record the estimate so it can be adjudicated (mirrors `decarb-plan` P2 conflict handling). Call `verifier__record_finding` with: - `asset_id` = the **Soapbox asset id** (not the Audette uid). - `kind`: `data-quality`. - `severity`: by materiality to the measure economics — **high** when the split is unconfirmed and drives a large electric or gas load (i.e. it swings IRRs materially), otherwise medium. - `evidence[]`: the per-fuel splits with their labels and the source behind each. - `sources[]`: every document, listing URL, and jurisdiction rule cited. - A summary that states the per-fuel landlord shares and their PRESUMED/CONFIRMED labels. Store the returned `finding_id`. In a `decarb-plan` engagement this finding is adjudicated at **Gate 1** alongside the other baseline conflicts — do not duplicate an existing open split finding; reference it (see the Cortland gas-split finding pattern in `decarb-plan` P1/P2). Resolve it via `verifier__resolve_finding` once the owner confirms. ## Audette landlord-share settings — MANDATORY write + read-back (not a 'note to self') When Audette is in play, the confirmed per-fuel split MUST be written INTO Audette, because **Audette's engine — not the Soapbox economics alone — computes which measure savings accrue to the owner.** A split that lives only in `metadata.utility_split` while Audette sits at its ~100% default yields overstated owner savings, IRRs, and value. This is not optional and is not a flag-for-later. Per building (Audette is building-level; a multi-building asset needs EVERY building set): 1. Look up the building model uid(s) for the asset (not the property uid). 2. Write `default_landlord_share_electricity` = and `default_landlord_share_natural_gas` = via the Audette building-edit tool. 3. Editing a building triggers a synchronous re-model that often exceeds the tool timeout; **the write still commits in the background.** Always **read the building back and confirm the value persisted** (retry any that rolled back). For many buildings, fire all edits first, then do one batch read-back pass rather than verify-each-inline. 4. Record in the engagement state which buildings were written AND verified. **Do NOT run or trust the decarb-plan / portfolio economics for an asset until its Audette landlord-share equals the confirmed split.** If Audette is unreachable (connector down/expired), STOP and tell the user to reconnect — never fall back to Audette's default and never silently compute at 100%.