Half-hourly energy data analysis for solar

Why your consumption profile matters

Solar electricity is worth most when you use it yourself, because it replaces power you would otherwise buy at your own unit rate. Exported power usually earns far less. In the shared worked example used across this site, on-site use is valued at an illustrative 24p per kWh and export at an illustrative 5p per kWh. Every unit you use rather than export is worth nearly five times as much.

So the question is not just "how much electricity do we use?" but "when do we use it?" Two sites with identical annual consumption can have very different solar cases. A cold store running around the clock uses solar output at almost any hour it is produced. An office that closes at weekends and shuts down in August will export more of its summer generation. Annual totals from bills cannot tell those two apart. Half-hourly data can.

What half-hourly data is

Half-hourly (HH) data records how much electricity your site used in each 30 minute period, 48 readings a day, usually for a year or more. It shows the shape of demand through the day, the difference between weekdays and weekends, and the swing between seasons. Matched against a solar generation model for the same periods, it shows how much of the output you would use and how much you would export.

How to get your half-hourly data

Most larger business sites already have it. Common sources:

1. Your electricity supplier. Many suppliers provide HH data through an online portal or on request. Ask for at least 12 months in a spreadsheet format.
2. Your meter operator or data collector. On HH metered supplies, the appointed data collector holds the readings. Your supplier can tell you who they are.
3. Smart or advanced meters. Many smaller business sites have smart or AMR meters that record half-hourly consumption, even if they are not billed that way.
4. Building management or sub-metering systems. Useful for understanding which parts of the site drive demand.
5. An energy broker or consultant, if you use one, may already hold the data.

You may be asked to sign a letter of authority so the data can be released to someone acting for you. If you share data with the installer, it should be used only to assess your site.

Profile classes and what they tell you

The first two digits on the top line of your MPAN are the profile class, which indicates how the supply is settled.

The industry is also moving all supplies to half-hourly settlement through the Market-wide Half-Hourly Settlement programme, so profile classes are becoming less important over time. If your bill shows 03 or 04, ask your supplier whether HH data is available from your meter.

What the analysis looks for

Baseload

Baseload is the demand that never goes away: refrigeration, servers, compressors, ventilation, lighting that stays on, process loads. It is the most valuable demand for solar because it is there whenever the panels are generating. A site with a high daytime baseload can usually take a larger system with high self-consumption.

Weekday and weekend patterns

Many businesses use much less electricity at weekends. In summer, a weekend can mean most of the generation is exported. The analysis quantifies this, and it often explains why the optimum system size is smaller than the roof could take, or why a battery or export-limited design is worth looking at.

Seasonal usage

Solar generation in the UK is several times higher in summer than in winter. Sites that use more power in summer, such as those with cooling loads, match well. Sites whose demand peaks in winter, such as those with electric heating, export more of their summer output. Schools are a classic case: high daytime use in term, very low in the summer holidays when generation peaks.

Peaks and capacity

The data also shows your maximum demand and how close you run to your agreed supply capacity. That matters for EV charging, battery sizing and the G99 application.

Self-consumption and payback

The shared illustrative example on this site is a 100 kWp system costing about £90,000 excluding VAT and generating about 90,000 kWh a year. With 80% used on site at 24p per kWh and 20% exported at 5p, the annual benefit is about £18,180 and simple payback is roughly 5 years before tax relief.

Here is how the same system changes with self-consumption, using the same illustrative prices:

These figures are illustrative and exclude maintenance, degradation, price changes and tax relief. They show why the analysis matters: getting self-consumption right is as important as getting the price right. Our solar payback page goes further, and the guide on how much solar your business needs covers sizing in more depth.

The battery case

HH data is also what tells you whether a battery is worth considering. If the analysis shows regular midday surplus followed by high evening or early morning demand, storing the surplus can raise self-consumption. If export is capped by the DNO, a battery can absorb output that would otherwise be curtailed. If your site uses almost all its solar output already, a battery for solar alone may not pay. See battery storage for business.

If you do not have half-hourly data

The analysis can still be done using monthly bills, a description of your operating hours and typical profiles for similar sites. The results are less precise, so the proposal should state the assumptions clearly and err on the cautious side for self-consumption. If you can get HH data later, the model can be re-run.

How the free survey uses your data

We arrange a free survey with one MCS certified installer matched to the site. If you share HH data or bills, the installer uses them to size the system against your actual demand and to estimate self-consumption, savings and payback. Your details go to that one installer only, and there is no obligation to proceed. See what the survey includes or request a free survey.