January 2027 price cap: kWh, a mains gas flag and tariff parameters, the cap's consumption basis, and Northern Ireland #2890

Activity

1. juaristi22

   assigned

   vahid-ahmadi

   on Nov 6, 2026
2. vahid-ahmadi commented on Nov 6, 2026

   

   vahid-ahmadi

   on Nov 6, 2026

   Collaborator

   More actions

   Thanks, María. This is a clear map of the gaps. I checked it against main at a866277 (2.175.8).

   Checks

   • Version. Main is at 2.175.8, not 2.174.1. The current-law pieces you list are on main: the indices came in 2.168.1, and the Household Energy Payment in 2.170.0. domestic_electricity_rate/great_britain.yaml holds 0% from 1 October 2026 and 5% from 1 July 2027.
   • The certified pair still pins 2.151.0. policyengine 6.15.0 on PyPI pins policyengine-uk==2.151.0, so managed_microsimulation() cannot see any of this yet. This is Certify a Microcosm build for policyengine-uk 2.175+ and bump the policyengine.py pin before 20 November uk-energy-price-cap-jan-2027#1. Until a certified Microcosm build and a pin bump land, any pe-uk change below will not reach the event's managed runs.
   • Item 1, kWh. Confirmed: both inputs are monthly, default -1, and their documentation says no dataset fills them. On has_mains_gas: an input cannot default to an expression, so it would be a formula variable with an override. gas_consumption is spending on all gas, and COICOP 04.5.2 includes bottled gas. We need to check that LPG homes do not read as on the mains before we use > 0.
   • Item 1, tariff split. Chronicle's regional nil and benchmark levels exclude VAT. A split derived from them is ex-VAT, so domestic_energy_vat can apply the rate without counting it twice.
   • Item 2. epg_subsidy.py does not read the cap. monthly_epg_consumption_level.py takes price_guarantee / price_cap, and only while energy_price_guarantee_in_effect is true (1 October 2022 to 31 March 2024). So no current-law output crosses the July 2026 break. It matters only for a reform that brings back a price guarantee.
   • Item 3, index. uprate_energy uses ONS CPI D7DT and D7DU and the OBR utilities path. These are UK series, not Great Britain ones, so Northern Ireland already moves on a UK index that includes it at its weight. The open question is whether Northern Ireland's tariffs track that index.
   • Item 3, council tax. simulated_council_tax already returns 0 for Northern Ireland, and the Household Energy Payment is England-only. Today the placeholder band reaches no amount; an unbanded member protects future band-keyed payments. Add it at the end of the enum (see Integer arrays passed to enum inputs are read as 0-based positions with no range check #2602).
   • Item 3, unused parameter. Confirmed. Under gov.contrib.policyengine.economy, only gdp_per_capita has a reader (household_market_income.py). rent.yaml and transport.yaml are unread too, so we can settle all three together.

   Overlap

   • Energy spending projection: add an energy-specific price index and a Microcosm release that writes energy_price_basis #2526: you are right that both remaining items are done. I will close it.
   • Correct the prepayment meter input's description #2882 fails "Fix evidence": its .fixed.md fragment makes it a fix PR, and Reproducer: n/a is refused because it touches model source. It only changes a description, so I will retype the fragment as .changed.md.
   • Mid-year parameter changes are dropped by fiscal year conversion #1807 (mid-year parameter changes dropped by the fiscal-year conversion) applies to quarterly tariff parameters.
   • Scottish Budget 2027-28: Scottish property income rates, council tax growth and a freeze switch, Bands I and J, and missing Scottish payments #2891 also changes CouncilTaxBand. One enum change should cover both.
   • Refresh Northern Ireland domestic rates growth for 2027-28 (due spring 2027) #2113 covers Northern Ireland's domestic rates growth, next to item 3.
   • The event repository already computes bills from kWh and rates in its own cap.py, and leaves Northern Ireland out of the cap shock. So none of these items blocks the event's own figures.

   Plan

   Item	Priority	Size	Owner	Next step
   #2882, #2883, #2884	Before the drill	Small	Vahid	Retype #2882's fragment; take all three out of draft for review
   Certified pair for 2.175+ (event #1)	Before the real event	Medium	Microcosm, policyengine.py	Ask for a certified build and a pin bump by 20 November
   has_mains_gas	Before the real event	Small	Vahid	Formula variable with an override, after the bottled-gas check
   Tariff split, GB average, Direct Debit	Before the real event	Medium	Vahid	Standing charge and unit rate by fuel for 2026 Q4 and 2027 Q1, from Chronicle
   Standing-charge and social-tariff levers	Before the real event	Medium	Vahid	Contributed reforms under gov.contrib with in_effect, current law unchanged
   Tariff split by region and payment method	Later	Large	Vahid	After the GB version, and with #1807 in mind
   Annual kWh inputs	Later	Medium	Vahid, Microcosm	Annual inputs plus a documented monthly split, once a kWh export is planned
   Cap basis (item 2)	Later	Small	Vahid	A typical_consumption sibling, only if a price-guarantee lever is planned
   Northern Ireland (item 3)	Later	Small to medium	Vahid	Document the UK-index choice; unbanded member with #2891; remove the three unused economy parameters

   Cold Weather Payment stays with #435 unless a change is announced.

   Please say if you disagree with this order.