Methodology Change History

2026-10-10

Refinements to smart control battery charging from the grid. This is now tested on dynamic tariffs only. The "Smart Control" toggle has been removed. Wrap-around data is now used for the "burn-in" period of the algorithim so that the dynamic charge algorithim covers the full comparison period, with no fixed-schedule prelude period.

Would-be solar clipping captured in battery. Some DC-coupled batteries can capture solar energy generation above the inverter AC limit, and the comparison tool now accounts for this. This refinement is enabled by default but can be toggled off under advanced options for users whose battery or inverter does not support this function. The battery maximum charge rate is still respected.

2026-10-09

Surplus-solar charging with fixed battery timers. Each grid-charge schedule is now tested with surplus-solar charging both enabled and disabled, including solar-only operation with no grid charging. Solar charging remains possible during discharge holds. The cheapest combination is selected per tariff and independently for winter/summer split scenarios. Solar charging is restricted to entered usage and meter data entirely before battery operation, avoiding double-counting historical capture.

2026-10-08

Refinement to threshold tariff cost calculations. Threshold tariffs (e.g. tariffs from Energia which have one unit rate for the first portion of usage each billing period, and a higher unit rate above the "threshold") are now priced in two-calendar-month periods, rather than on a blended yearly basis. This provides a better estimate of overall above-threshold consumption. The refinement is most impactful for housholds with highly seasonal electricity use (e.g. those with heat pumps).

Upcoming rate changes priced as separate periods. An announced price change within the 12-month window is no longer blended into a single day-weighted average of the rates. The current and upcoming rate sets are now priced as two separate periods: usage is charged at the rate in force on each calendar day of the coming year (short uploads instead split usage by day proportion), while standing charges, threshold allowances and all gas costs always split by day count. Only the changed rates appear, shown as paired “Current” / “After [date]” rows. The dynamic wholesale-linked component, and the dated PSO and carbon-tax schedules, are unaffected.

2026-09-15

Winter/summer switching scenario. Full-year electricity comparisons now independently simulate winter (Jan–Mar and Oct–Dec) and summer (Apr–Sep), choosing each season's cheapest tariff including its exit fee. A clearly labelled split scenario joins the ranked results only when the two winners differ and their combined cost beats the cheapest single tariff. Both exit fees are included, annual welcome credits are excluded, and annual fixed charges and threshold allowances are prorated. Electricity custom-discount edits now refresh the comparison on blur/Enter so seasonal winners stay consistent. Gas, dual-fuel and separate solar projections are unchanged.

2026-09-13

User-customised discount rates. Tariff cards that show a discount now have a pencil icon in the Discount Rate column header allowing you to set a custom discount percentage. The card re-prices immediately: unit rates are re-derived from the published standard rate at your discount (standing charges, PSO levy and export credits are unaffected, matching how discounts actually work). Customised cards are marked "User Customised [Reset]" with a distinguishing outline, each discount-permutation option is customised individually, and Reset restores the published figures.

2026-09-03

Battery simulation overhaul and synthetic load profile refinement:

• Explicit charging schedules on every battery result card. Cards now describe the exact charging schedule assumed in each estimated price (e.g. 23:00–08:00 Night windows, EV-rate windows, peak-hold variants).
• Two explicit charging policies. Households with batteries can compare prices under a Fixed Timer (the default: a tournament across candidate windows generated from the tariff's rate bands) or Smart Control (day-ahead price-following automation with a 4-week trailing load forecast). When Smart Control is off, cards indicate the additional potential savings from automation.
• Chronological simulation. Charge and discharge are simulated chronologically across 23:00-anchored planning days, carrying state of charge across days and preventing impossible time-travel discharges.
• Economics-based cycling. A marginal arbitrage test with a 4 c/kWh wear threshold ensures cycles are worthwhile after losses and degradation. Smart Control charges at maximum rate in deeply discounted bands (e.g. an 8c EV band under 24c Night rates) and decides discharge each half-hour from the current price versus the marginal value of stored energy over the day's remaining forecast demand, replacing the previous static reserve curve.
• Smarter forecasting, validated. The load forecast now sees the full simulated household (EV charging and shifted loads included), not just the non-shiftable baseline. With perfect hindsight the policy lands within ~1–2% of the theoretical optimum for any causal controller; without hindsight it matches or beats the best fixed schedule in most configurations.
• Default charge rate reconciled to 3 kW, matching the single-phase domestic standard and the existing UI input.
• Synthetic load profile weekly rhythm restored. The default synthetic profile (used when comparing by estimated annual kWh) now preserves realistic day-to-day and week-to-week autocorrelation, using 4 continuous 13-week seasonal blocks from UK Power Networks London household data calibrated against the Irish RMDS LP1 profile. The previous construction drew single days from 365 distinct households, breaking weekly habit persistence.

2026-08-04

Major methodology overhaul: the comparison tool was replaced by a ground-up rewrite. The previous methodology page is archived verbatim at Electricity Price Comparison Methodology (Archived). Headline changes:

• Tariff-dependent load shifting. The choice of tariff now affects when flexible loads (battery, EV charging, other large shiftable loads) are scheduled: for each tariff structure, movable load is placed into that tariff's cheapest hours before pricing, rather than pricing every tariff against one fixed schedule. This makes comparisons fairer for households with batteries, EVs, solar panels and heat pumps — these households will see the largest changes versus the old tool.
• New synthetic load shape for annual-kWh comparisons. Estimated-consumption comparisons now use a half-hourly load shape built from the Irish 2026 RMDS standard load profile (daily shape and seasonality) combined with UK Power Networks 2011–2014 household data (half-hourly texture and day-to-day volatility), replacing the old flat day/night/peak split (54%/36%/10%). The band-allocation slider was removed as a consequence: you can no longer override the time-of-day split, because the model now derives a full half-hourly shape instead.
• More conservative solar savings. Solar self-consumption is now modelled at sub-half-hour resolution: within a single half-hour you can import a little and export a little at the same time, and the residual export is worth less than avoided imports. The old model assumed all solar produced within a half-hour offset imports, so modelled solar savings are now lower (and more realistic). Inverter clipping is still applied and is now variance-aware; the inverter capacity (default 5.5 kW) is now user-editable under the solar Advanced options.
• Maximum import capacity default changed from 16 kW to 12 kW (the standard domestic connection), with an "Enhanced supply (16 kW MIC)" toggle for homes with an enhanced connection. Households that would previously have been modelled at 16 kW may see reduced modelled battery/EV stacking unless they tick the box.
• Some legacy-only advanced controls were retired (e.g. the current-supplier field and user-set battery/EV schedules) — scheduling is now decided per tariff inside the comparison.

2026-02-21

Added Maximum Import Capacity 12 kW option for throttling EV charging to a total import rate of 12 kW rather than the default 16 kW. Available under "Advanced Options" when the EV slider is set to a non-zero value.