TRANSPARENT BY DESIGN

How Hearthline works.

Version 2.1 · Last reviewed 11 August 2026

How the quote workspace score works. The score is the percentage of listed comparison fields and evidence statements marked present. Every item has equal weight in the first release. It measures documentation completeness only—not technical quality, price fairness, installer competence or likely system performance.

How Project Controls work. Budget, contract, payment, evidence, snagging and handover statuses are records entered by the account holder. Hearthline calculates totals and highlights incomplete or overdue records, but does not verify the underlying document, approve a payment or certify that work is complete.

Hearthline is a planning tool, not an EPC assessment, building survey, heat-loss calculation or installer quote. It is designed to help homeowners ask better questions and compare broad options before paying for professional advice.

What the model uses

The plan combines the property type, age, floor area, heating fuel, existing improvements, energy use, tariff, budget and priorities supplied by the user. If exact consumption is unavailable, Hearthline estimates it from the property and occupancy answers, then scales the result to the annual bill when one is provided.

Input	Default source or approach	Review cycle
Electricity and gas rates	Ofgem GB direct-debit averages	Quarterly
Solar and heat-pump central costs	Energy Saving Trust published guidance	Six-monthly
Heat-pump grants	Ofgem and GOV.UK scheme pages	Quarterly and at policy changes
Measure savings	Published UK benchmarks, scaled to modelled energy spend	Six-monthly

Why results are ranges

Installer prices, weather, occupancy, workmanship, moisture risk, orientation, shading and behaviour differ. Hearthline places a range around the central planning case and offers conservative, typical and optimistic saving scenarios. These are not confidence intervals or guarantees.

How measures are ordered

Measures begin with a base priority reflecting disruption, cost and building sequence. The ranking is then adjusted by the user’s priorities. Comfort gives more weight to fabric measures; bill savings favour controls, insulation and solar; carbon gives more weight to solar and clean heat. Product configuration is separate and is not read by this calculation.

Important limitations

No postcode-level weather, roof geometry, orientation, shading or local labour pricing is modelled.
Indicative EPC bands are deliberately not predicted; only an accredited assessment can establish an EPC rating.
Historic, listed, solid-wall and damp-affected homes require specialist moisture and conservation advice.
Heat-pump running costs depend on room-by-room heat loss, emitter sizing, flow temperature and achieved seasonal performance.
Grant rules and tariffs change. Always check the linked official source before committing.

Commercial independence

Hearthline funds the free planner and guides through optional tools it creates and clearly labelled paid partner links shown after relevant guidance. Neither product nor partner configuration supplies the ranking, saving model or editorial wording. Partner data is not read by the recommendation engine and paid relationships do not create installer rankings. Read how Hearthline earns money.