Start with volume, not price
Pull twelve months of kWh by month. Adjust for anything you know is changing — new equipment, extra opening hours, a site closing. Volume is the part of the forecast you actually control.
Layer in contracted and uncontracted periods
Apply your contracted unit rate and standing charge to the months already covered. For uncontracted months, use a conservative forward estimate rather than today's price, and flag it as an assumption.
Add non-commodity and review quarterly
Network charges and levies change annually and rarely downward. Build in a modest uplift, then revisit the forecast each quarter as actuals arrive. A forecast reviewed quarterly is a management tool; one built once a year is a guess.
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