How Household Utility Bills Are Estimated

概要

The utility bills calculator estimates total monthly running costs for a UK household. It combines seven categories — electricity, gas, water, council tax, broadband, TV licence, and home insurance — into a single monthly total. Energy costs are driven by property type and household size, using Ofgem price cap rates and typical consumption data. Other costs use national averages as defaults, adjustable by the user.

仕組み

The calculator estimates household bills in two groups:

Calculated costs (derived from inputs)

1. Electricity — annual kWh consumption (from property type × household size lookup) multiplied by the unit rate, plus a daily standing charge.
2. Gas — same approach as electricity, with separate kWh consumption and rates. Can be toggled off for all-electric homes.
3. Council tax — the England average Band D rate (£2,280/year for 2025/26), scaled by the statutory band multiplier.
4. TV licence — the fixed annual fee of £174.50 for 2025/26.

Pass-through costs (user-entered)

5. Broadband — default £31/mo (UK average).
6. Water — default £50/mo (national average £603/year from Water UK).
7. Home insurance — default £32/mo (combined buildings + contents average £384/year from ABI).

Energy consumption data

Annual electricity and gas consumption varies by property type and household size. The values are derived from Ofgem Typical Domestic Consumption Values (TDCVs) and Energy Saving Trust property-type breakdowns:

Values shown as electricity / gas kWh per year. The medium semi-detached figures match Ofgem’s medium TDCVs (2,700 / 11,500 kWh).

Council tax band multipliers

Council tax is charged as a fraction of the Band D rate, fixed by statute:

計算式

計算例

The energy total of £1,757.50/year aligns closely with Ofgem’s typical dual-fuel cap of ~£1,758/year for a medium household.

入力値の説明

• Property type — flat, terrace, semi-detached, or detached. Determines energy consumption from the lookup table.
• Household size — small (1-2 people), medium (2-3 people), or large (4+ people). Combined with property type for energy lookup.
• Gas supply — toggle on/off. All-electric homes skip gas costs entirely.
• Council tax band — A through H. Determines the multiplier applied to the England average Band D rate.
• Broadband, water, insurance — direct monthly amounts. Defaults reflect UK averages (broadband £31/mo, water £50/mo, insurance £32/mo).
• Energy rates — hidden behind “Adjust energy rates”. Default to the current Ofgem price cap. Override for users on fixed tariffs or different suppliers.

出力値の説明

• Total monthly bills — the hero metric, summing all seven categories.
• Energy card — combined electricity + gas monthly cost with individual breakdown.
• Council tax card — monthly council tax showing the selected band.
• Bill breakdown chart — stacked bar and legend showing each category’s share of the total.
• Energy consumption insight — estimated annual kWh for electricity and gas.

前提条件と制限事項

• England only for council tax. The Band D average (£2,280) is the England average. Scotland, Wales, and Northern Ireland use different council tax systems with different band structures and rates.
• Energy rates are GB national averages. Ofgem price cap unit rates and standing charges vary by region (14 electricity regions, 8 gas regions). The defaults are GB-weighted averages.
• Consumption estimates are approximate. The property type × household size matrix is derived from Ofgem TDCVs and Energy Saving Trust data. Individual households vary widely based on insulation quality, appliance efficiency, heating habits, and occupancy patterns.
• No seasonal variation. Energy costs are averaged over the year. Winter gas bills can be 3-4× summer bills.
• Static energy rates. The Ofgem price cap changes quarterly. The defaults reflect Q1 2026 (Jan-Mar). Users should update rates when Ofgem announces new quarterly caps.
• Water costs are not property-dependent. In reality, metered water charges vary by usage and region. The default is the national average.
• Home insurance varies widely. The £32/mo default is the ABI average for combined buildings + contents. Actual premiums depend on property value, location, and claims history.

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