Why office buildings hit higher self-consumption than warehouses

Self-consumption is the single biggest economic lever

The economics of a commercial solar PV installation come down to a remarkably simple equation. Every kWh the system generates is worth either your avoided grid retail price (currently 25-40p/kWh for most UK commercial customers) or the SEG export price (currently 5-12p/kWh). The fraction split between those two prices is what’s called the self-consumption ratio.

For a typical UK commercial customer, the difference matters enormously. At 30p/kWh retail and 9p/kWh SEG, every percentage point of self-consumption is worth 21p × annual generation. On a 300 kWp office system generating 276,000 kWh/year, every 1% of self-consumption is worth £580/year — about £14,500 over 25 years.

Across the typical 50-percentage-point range between low-self-consumption and high-self-consumption commercial installations, that’s the difference between a 4-year payback and an 11-year payback.

Why offices win

Office buildings hit higher self-consumption ratios than almost any other commercial building type. The reason is in the demand profile.

A typical UK office runs at 60-90% of peak demand from 8am to 6pm, Monday to Friday. Cooling load dominates summer demand and aligns almost perfectly with solar generation. IT and lighting baseload provides 24-hour minimum load that absorbs morning and afternoon generation. Hybrid working has slightly reduced peak demand but increased the daytime baseload across more days of the week (Tuesday-Thursday especially), strengthening self-consumption further.

The typical UK office without battery storage hits 70-85% self-consumption on a well-sized PV system. With a 200-400 kWh battery, that lifts to 90-95%.

By contrast, a typical UK warehouse runs at lower daytime demand (lighting and MHE only, no significant cooling load), often operates on 24-hour shift patterns where night-time consumption is the dominant load, and has minimal weekend demand. UK warehouses without battery typically hit 40-55% self-consumption — meaning roughly half of generation exports to SEG at low tariffs.

A retail building with no air-conditioning sits somewhere between — maybe 55-65% without battery. A factory with high process load and three-shift operation can hit 80%+ without battery but often has roof constraints that limit system size.

What this means for sizing

Higher self-consumption means a larger economically-optimal system. An office that can absorb 80% of generation can justify a system sized to 80% of annual demand. A warehouse that only absorbs 50% of generation should be sized to 50% of demand (or smaller) — anything larger pushes the additional generation into export at unfavourable tariffs.

This is why generic kWp-per-sqm-of-roof rules of thumb produce worse outcomes for offices than for warehouses. The office can typically support a larger system economically; the warehouse should typically be smaller.

Working out your specific self-consumption

The half-hourly meter data approach we use models self-consumption explicitly. For a given system size, we overlay 12 months of historic generation (from PVSyst model, building-specific) onto 12 months of historic consumption (from meter data, building-specific). The result is a half-hour-by-half-hour record of when the building self-consumes generation, when it exports, and when it still imports from grid.

That model is then used to project economics across the 25-year asset life — varying the SEG tariff assumption, the grid retail price escalation, and any future changes to building load (planned EV charging, heat pump retrofit, etc.).

The output is a specific self-consumption ratio for your building, your load shape, and your roof — not a generic industry assumption.

Tactics to lift self-consumption

For office buildings already on a good baseline, several measures lift self-consumption further:

Battery storage. 200-400 kWh covers the typical morning-peak / late-afternoon-peak shift. Lifts self-consumption by 10-20 percentage points.

Workplace EV charging. Daytime EV charging from solar generation creates additional Monday-Friday daytime load. 10-20 × 7-22kW chargers absorb meaningful generation in the spring/autumn shoulder season.

Building cooling pre-cooling. BMS strategies that run cooling slightly harder in summer afternoon (when generation is highest) can shift consumption into the generation window without affecting occupant comfort.

Process load timing. For offices with significant kitchen, server cooling, or other shiftable loads, scheduling these to align with generation peaks lifts self-consumption further.

We model these tactics in every proposal — the marginal economics are often surprisingly significant.

Request a free feasibility study modelled from your specific load profile.