Setting a Performance Baseline

A performance baseline is a dated record of how a home performs before work starts, so later change can be judged rather than guessed. It has three parts: the paper baseline, meaning the current certificate and any audit; the meter baseline, meaning readings and bills over a representative period; and the lived baseline, meaning notes on comfort, draughts, condensation and room use. Without all three, a later claim of improvement rests on memory, which is unreliable across seasons.

Consider a household insulating its loft in autumn and then reporting lower bills in winter. Without a baseline, nobody can tell whether the saving came from insulation, a milder winter, a tariff change, or simply heating fewer rooms. With a baseline recording the previous winter's readings, heating hours and outdoor temperatures, the comparison becomes fair, and the household can tell whether work helped, by how much, and where it did not.

The paper baseline starts with the certificate: its date, rating, assumed construction, heating system and recommendations. Add any audit report, survey, previous quotes and records of work already done, with dates. Note which certificate inputs were assumed rather than observed, because those are inputs a new assessment after work should correct with evidence. A paper baseline with gaps is still useful, provided gaps are marked as gaps.

The meter baseline needs time. A single reading proves nothing, but monthly readings over a full year, or at least over a heating season, show patterns: winter peaks, summer baseload for hot water and appliances, and effects of holidays or occupancy changes. Where smart meter data is available, half-hourly patterns can show heating hours and overnight use, but even a notebook of monthly readings is enough, provided readings are taken at the same time each month.

Check the certificate date first. A certificate issued ten years ago may describe a home that has since had new windows, a new boiler or an extension, and using it as a baseline without noting those changes will mislead every later comparison. If work has been done since the certificate, record it with dates and evidence, and consider whether a fresh assessment is needed before further work.

Check meter access and reading method. Note whether readings are actual or estimated, whether gas and electricity are on separate meters, and whether any fuel such as oil, wood or LPG is bought in bulk and therefore needs delivery records rather than meter readings. Estimated bills, common when readings are missed, should be marked as estimates and replaced with actual readings as soon as possible.

In the UK, the EPC register provides a public paper baseline for many homes, with certificates searchable by address in England, Wales and Northern Ireland, and a separate register in Scotland. That public record is useful, but it is only as current as its last assessment, and it does not include meter data or lived experience, so it should be supplemented with household records rather than treated as a complete baseline.

In EU member states, certificate registers and formats are national, and access rules vary: some registers are public, others require owner consent or assessor access. The baseline principle is the same, but the paper starting point may be a national certificate with a different rating scale, validity period and recommendations. Note the national system and its date whenever you record a baseline from an EU certificate.

The most common baseline mistake is starting work before recording anything. Once loft insulation covers the old depth, or a boiler is removed, the before picture is gone, and every later claim becomes an estimate. A week of notes and a set of photographs before work starts costs almost nothing and preserves evidence that cannot be reconstructed afterwards.

A second mistake is recording only bills, without context. A bill reflects tariff, standing charges, estimated readings and occupancy as well as energy use, so a bill reduction after work may reflect a tariff change rather than a building improvement. Record meter readings in kilowatt-hours, separately from cost, and note tariff changes, so energy and cost can be tracked as separate stories.

Keep the baseline as a single dated file: certificate copy, meter reading log, bill copies with actual versus estimated marked, comfort and draught notes, and dated photographs of lofts, walls, boilers and windows before work. Store a copy away from the home if possible, so the record survives a move, and update it after each phase of work with a new dated snapshot.

Ask a professional what baseline they need before quoting, and whether they will take their own readings or rely on yours. A professional who starts work without asking about the existing certificate, meter history or comfort problems is planning without a starting line, and their later claim of improvement will be hard to verify.