Calculation Methodology

Data Collection Principles

All calculations use primary source data from official regulators and government departments. We never use secondary sources, comparison sites, or outdated data.

Energy Bill Calculations

Energy costs use Ofgem's Typical Domestic Consumption Values (TDCV) and current price cap rates. Calculations include:

• Standing charges (per day) × 365 days
• Unit rates (per kWh) × annual consumption
• Regional variations for electricity distribution
• Payment method differences (direct debit vs prepayment)

Water Bill Methodology

Water bills use published tariffs from each regional water company for 2026-27. Calculations account for:

• Unmetered charges by council tax band (most common)
• Metered charges where applicable
• Separate Scottish Water banding system
• Surface water drainage charges

Verification Schedule

Data is verified on the following schedule:

• Energy: Within 24 hours of Ofgem announcements
• Tax rates: Updated for each new tax year (6 April)
• Water rates: Annual update (1 April)
• Council tax: Annual verification against MHCLG data
• Full audit: Bi-weekly verification of all sources

Quality Assurance

Every calculation is tested against worked examples from the original source documentation. We maintain automated checks to prevent data staleness and architectural regression.