How to calculate your business electricity costs

Calculating your business electricity cost accurately means combining three elements: your annual consumption in kWh, your unit rate in pence per kWh, and your daily standing charge, rather than relying on a single bill or a supplier's headline figure.

Start by finding your annual consumption. This is usually available on your online supplier account, or can be calculated by adding together twelve consecutive monthly bills. If your usage is seasonal, a full year gives a far more accurate picture than any shorter period.

Next, confirm your unit rate. If you are on a fixed contract this should be stated clearly in your contract paperwork. If you are unsure, your latest bill will show the rate applied for that billing period, though note this may include VAT and levies depending on how the supplier presents it.

Multiply your annual kWh consumption by your unit rate to calculate the commodity cost. For example, 22,000 kWh at 27p per kWh equals £5,940.

Add the standing charge. Multiply your daily standing charge by the number of days in the year, 365 or 366. At 48p per day, that is £175.20 across a 365-day year.

Add the two figures together for your pre-VAT annual electricity cost: in this example, £5,940 plus £175.20 equals £6,115.20.

Apply VAT, typically 20% unless your business qualifies for the reduced 5% rate due to low consumption or partly domestic use of the premises. At the standard rate, £6,115.20 becomes £7,338.24 including VAT.

If your bill also shows the Climate Change Levy separately, add this too: it is charged per kWh in addition to the unit rate, and the exact rate is set annually, so check your latest bill or contract for the current figure applied to your account.

For half-hourly metered businesses, a capacity charge may also apply, based on your agreed maximum demand rather than your consumption, and this should be added as a separate fixed annual cost on top of the standing charge and commodity total.

Once you have this full calculation for your current contract, you can apply the same method to any new quote using the same consumption figure, which gives you a true side-by-side comparison rather than relying on unit rate alone.

Repeating this calculation at each renewal, using your latest twelve months of actual consumption rather than an old estimate, ensures your comparison reflects how your business is genuinely using electricity now, not how it used it several years ago.

If your business has a capacity charge as a half-hourly metered site, calculate it separately using your agreed kVA or kW capacity multiplied by the supplier's or network's capacity rate, then add this figure to your commodity and standing charge total before applying VAT, since omitting it will understate your true annual cost, sometimes significantly for sites with a large agreed capacity relative to actual usage.

A simple way to sense-check your own calculation is to compare the result against your actual annual spend as shown on your last twelve invoices added together. If the two figures differ by more than a small margin, it usually points to either a change in consumption partway through the year, a mid-term rate change under a pass-through contract, or an error worth querying with your supplier directly.

Before running the calculation, it helps to know roughly which bracket your business sits in, since a café working from 8,000 kWh a year will use a very different unit rate assumption to a workshop running machinery at 150,000 kWh, and starting with a realistic expectation makes it easier to spot a genuinely odd figure on your bill.

It is worth running this exact calculation again a few months before your contract ends, using your termination notice period as the trigger, so you have a clear, current cost figure ready the moment you start requesting comparison quotes rather than scrambling to pull invoices together at the last minute.

Once you have a reliable annual figure calculated this way, keep it somewhere easy to find alongside your MPAN and contract end date, since that single number is exactly what you, or a broker acting on your behalf, will need to put in front of suppliers to get an accurate like-for-like quote.