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Understanding Unit Rates on Your Energy Bill

Unit rate is the price per kilowatt-hour (kWh) before you stack standing charge, CCL and VAT. On UK business bills it may be split by time-band, bundled inside a fixed product, or exposed on pass-through deals—this guide turns p/kWh deltas into yearly cash.

Next step: If you use under about 50,000 kWh a year, you can get a quote in under 90 seconds online — fast, no obligation. Larger supply, half-hourly metering, or prefer chat? Use the contact page.

Unit rate as marginal cost

Think of p/kWh as the incremental cost of the next thousand hours of a 1 kW heater. Standing charges are sunk the moment the supply energises; unit rates scale with production, opening hours and weather. That distinction matters when someone proposes LED retrofits or compressor scheduling—“we saved 6% on kWh” only lands if the marginal rate applied to the kWh you removed was the one you modelled (correct register, correct tax treatment).

Single-rate, time-of-use and half-hourly reality

Classic SME meters may still show one “all-in” day rate; Economy 7-style splits display separate day and night registers; half-hourly HH settlements cost-follow more granular DUoS bands even if your PDF summary collapses them. If your contract lists multiple p/kWh cells, build a usage-weighted average: multiply each band’s kWh by its rate, divide by total kWh, then compare that blended figure across suppliers—not the daytime cell alone.

Lapsed fixed deals often dump you onto deemed rates where the published p/kWh bears no resemblance to last year's renewal pack—that is a tariff class change, not a gentle tweak.

Fixed commodity vs pass-through commodity

In a fully fixed SME product, the supplier typically absorbs wholesale and many policy swings inside the agreed p/kWh (subject to contract carve-outs). In pass-through or hybrid structures, your statement may show a slim energy slice and separate schedule lines that reprice monthly or quarterly. Neither approach is “better” in the abstract; the question is whether you wanted budget certainty or transparency. When benchmarking, copy the supplier’s definition of what is inside that p/kWh cell from the terms, then align standing charges alongside.

Worked comparisons you can photocopy

Example A. Quote 1 offers 27.4p/kWh; Quote 2 offers 25.9p/kWh. Annual consumption 18,000 kWh. Delta = 1.5p/kWh → 0.015 × 18,000 = £270/year on commodity alone.

Example B (CCL). Main-rate electricity CCL is £0.00775/kWh in 2025–26. It rides on qualifying kWh, not on standing charge. An extra 1,000 kWh of summer cooling therefore adds roughly £7.75 of CCL on top of the extra commodity itself—budget both when modelling peaks.

Example C (percentage language). If someone says “8% wholesale rise adds 2p,” sanity-check against your actual p/kWh. On a 30p base, 8% is 2.4p; on a 22p base it is only 1.76p. Always multiply percentages from the right baseline.

Quote comparison cheat sheet

Use the same table inside your quote comparison workflow; reconcile awarded rates back on the bill with bill reading.

When the unit rate on the bill “drifts” legitimately

Mid-term blend of an old rate, a renewal rate, and a deemed bridge produces weighted averages that do not match any brochure. Likewise, pass-through adjustments can post one-off p/kWh corrections. Build a month-by-month spreadsheet if variance exceeds a few percent; if it tracks your contract ladder, you are done—if not, escalate using the dispute path in our companion piece on billing complaints.

Index-linking and “cap plus” language

Some contracts reference published indices or supplier price books that move quarterly. Your unit rate may therefore rise 0.8p without any wholesale headline drama simply because a passthrough reconciliation posted. Ask for the triggering event in writing (dates, formula, rounding). If the contract promises a fixed p/kWh but footnotes allow pass-through “when materially different,” push for a quantitative threshold—vague materiality invites billing arguments later.

Green premiums sometimes appear as a separate micro-rate per kWh atop commodity; others fold REGO costs into one cell. For marketing compliance, you need the split even if treasury only cares about totals—finance and brand risk are linked when public claims reference “renewable supplied at no extra cost.”

Related guides

See also high bill diagnostics, multi-site energy management, and the energy hub.