The audit-to-solar pathway

Most commercial solar proposals are sized from a bill total and a roof plan. The good ones are sized from audit data — and the difference shows up every year for twenty-five years. Here is the order of operations that gets the investment right.

Why the audit comes first

Commercial solar economics live and die on self-consumption: the share of generated electricity you use on site rather than export. On-site use displaces electricity at your full retail rate; exports earn a fraction of it. Self-consumption depends entirely on when you use energy — which is exactly what half-hourly audit analysis establishes, profile by profile, site by site.

The audit also changes the size of the problem before anything goes on the roof. If lighting upgrades, controls fixes and out-of-hours waste recovery cut consumption 15–20% — a normal audit outcome — then the correctly sized array is materially smaller and cheaper than the one a bill-based proposal would have specified. Efficiency first, generation second is not a slogan; it is the sequencing that stops you buying panels to serve waste.

What audit data answers that a sales survey cannot

• True self-consumption modelling. Half-hourly demand laid against modelled generation, season by season — not an assumed percentage. Daytime-heavy operations routinely support 70–90% self-consumption; a weekend-shutdown site might not.
• Post-efficiency sizing. The array sized to the consumption you will have after the savings register is delivered, not the consumption you had last year.
• Tariff reality. Demand charges, time-of-use bands and capacity costs from your actual contracts, so the saving is calculated against the rates you genuinely avoid.
• Battery and load-shifting cases. Whether storage or rescheduling flexible loads (compressors, chillers, charging) beats grid export — answerable only from profile data.
• The reporting dividend. Every self-consumed solar kWh cuts reported Scope 2 emissions, flowing straight into SECR disclosures and any net-zero pathway your board has signed — and if that pathway is still being scoped, specialists such as carbon consultancy Carbon Legacy turn audit outputs into a costed plan.

A worked illustration

A distribution operator with a £180,000 annual electricity spend asks for a solar quote and receives a proposal for a 500 kWp array. The audit runs first instead: out-of-hours conveyor and compressor waste plus an LED completion cut the baseline by 14%. The half-hourly profile shows a hard 6am–8pm operating window with weekend shutdowns, capping sensible self-consumption. The right answer turns out to be 350 kWp plus load-shifting of battery charging into the solar window — roughly 30% less capital for almost the same annual saving, and a payback under six years instead of eight. Nothing exotic happened; the data was simply allowed to size the system.

How the pathway runs in practice

1. Audit. The standard audit process — data analysis, site survey, costed savings register.
2. Deliver the quick wins. Controls, scheduling and lighting measures first; they shrink and reshape the load profile.
3. Model generation against the new profile. Roof capacity, orientation and structural checks meet the post-efficiency demand curve.
4. Tender with the numbers fixed. Installers price a specified system against a verified profile — competitive, comparable bids instead of competing guesses. Specialist commercial installers take it from there.
5. Verify. Post-installation, the same metering that powered the audit confirms the system performs to model — and feeds the next year's disclosures.

The audit fee is a rounding error inside a six-figure solar decision. Taking the steps in this order is the cheapest insurance available on that capital — and it is why we built the pathway as a single engagement. Costs for the audit stage are on the cost page.