Half-Hourly Electricity Data: Why It Matters for Commercial Solar

What half-hourly data is

Electricity is bought and sold in half-hour periods, and a half-hourly meter records how much you used in each one. A year of it is a spreadsheet with one row per half hour, or one row per day and 48 columns. Plotted, it shows the shape of your day: when the site wakes up, the peaks around production or opening hours, the overnight base load from fridges, servers and lighting, and how weekends and seasons differ.

A monthly bill hides all of that. Two businesses that each use the same amount a year can be very different solar sites if one runs from 7am to 5pm and the other mostly at night.

Do I have a half-hourly meter?

Your bill shows the full MPAN (meter point administration number), 21 digits laid out in a box. Elexon, which runs electricity settlement, says the first two digits give the profile class (Elexon):

Since 6 April 2014, meters in profile classes 5 to 8 have had to be advanced meters that can be read remotely and record half-hourly consumption, and since 1 April 2017, under the industry change P272, those supplies have had to be settled half-hourly where capable metering is fitted (Elexon P272). Larger sites usually have a half-hourly meter already. Smaller businesses with a smart or advanced meter usually have half-hourly readings too, even if they are billed monthly.

The industry is moving every meter to half-hourly settlement. The MHHS Programme says the 18-month migration of meters to the new arrangements is under way (MHHS Programme).

How to get 12 months of data

• Find each MPAN. One per electricity supply. Sites with several buildings often have more than one
• Ask your current supplier. For the last 12 months of half-hourly consumption data for each MPAN, as a spreadsheet (CSV or Excel)
• Changed supplier this year?. Ask the previous supplier for its months too
• Check it covers a full year. Twelve months shows summer and winter, holidays and seasonal peaks
• Send it with your enquiry. Or keep it ready for the installer at the survey

If your supplier can only give monthly figures, send 12 months of bills and a note of your opening hours and the main equipment on site. The installer can work from that; the estimate is just less precise.

What it shows about your daytime use

The installer will look at three things in the data:

• Daytime load. How much the site uses in daylight hours, which are long in summer and short in winter, when panels produce
• Base load. What runs all the time: refrigeration, compressors, servers, ventilation. Solar covers its daytime share
• Weekends and holidays. Output on days the site is closed is exported unless a battery or another load takes it

How it is used to size solar and batteries

Most of the value of commercial solar comes from electricity you use yourself, because that replaces power you would otherwise buy. With a year of half-hourly data, an installer can lay a modelled solar output for your roof over your actual use, half hour by half hour, and see how much would be used on site and how much exported. That is how they choose a size that suits the business rather than one that simply fills the roof. Our guide to how much solar a business needs goes through the method.

The same data shows whether a battery would help: if the site exports a lot at midday and buys a lot in the evening, there may be a case; if it uses everything the panels make, there usually isn't. See commercial battery storage.