Half-hourly data shows when a potential client’s site uses electricity and how demand changes throughout the day. You can use these insights to size solar panels and batteries more accurately, estimate potential savings, and compare different project options.
Below, we explain how half-hourly data analysis works and how to use it when planning a commercial solar PV or battery storage project.
What is half-hourly data analysis?
Half-hourly data analysis shows how a site’s electricity use changes throughout the day and over longer periods.
A half-hourly electricity meter records the site’s consumption across 48 settlement periods each day, beginning on the hour and half-hour. When the clocks change, a day has 46 or 50 instead.
Each half-hourly reading shows how much electricity the site used, measured in kilowatt-hours (kWh). Double that figure to calculate the site’s average demand in kilowatts (kW) during the half hour.
For example, if a site uses 40 kWh between 9 a.m. and 9:30 a.m., its average demand was 80 kW: 40 kWh × 2 = 80 kW
The data also contains:
- Grid import readings: electricity taken from the grid
- Grid export readings: electricity sent back to it (on suitable sites)
- Annual total: how much electricity a site used over one year
The value of half-hour data analysis is that it helps installers match proposed solar generation and battery use to the customer’s actual demand.
How do you analyse half-hourly electricity data?
These are the seven main steps in half-hourly electricity data analysis:
1. Collect enough electricity data from the client
Ask for at least 12 complete months of readings. You need a full year’s worth of information to see usage patterns across summer, winter, weekends, holidays, and different seasons.
Get the client to obtain their half-hourly meter data from their electricity supplier. Some suppliers provide metering portals for client self-service while others send out the readings by email following a request. Another approach is to have the customer sign a Letter of Authority so the supplier can dispatch the data directly to you.
The file normally comes to you as a CSV file or an Excel spreadsheet.
If you can, collect the client’s recent electricity bills so you confirm the meter, tariff, annual consumption, and the total cost of the electricity used during the same period.
Make sure to check the Meter Point Administration Number, or MPAN, on the bill and in the data file. The MPAN identifies the electricity supply that the meter records.
Larger prospects may have more than one MPAN on their electricity bill. If that’s the case, you’ll need the half-hourly meter data for each supply to see the site’s full electricity use.
2. Check the readings
Before running your full analysis, it’s important to run a check for missing readings, duplicate readings, wrong dates and periods that appear in the wrong order. If you don’t, this often leads to incorrect system sizing and savings estimates.
Pay particular attention to the GMT and BST changeovers. These days contain 46 or 50 settlement periods rather than 48, so use the period number and time-zone label to place each reading correctly and avoid treating repeated autumn readings as duplicates.
Typical reading issues to look out for include:
| What to look for | What it could mean | What to do |
|---|---|---|
| Long runs of zero use | The site may have been closed, lost power, or have missing readings. Solar may also have covered all demand for a short time. | Compare the dates with closures, power cuts, and opening hours. Check with the supplier that no readings are missing. |
| The same reading repeated many times | The supplier may have copied or estimated the values because no new meter reading was received. | Check whether the readings are actual or estimated. Don’t treat them as normal until you know why they repeat. |
| Negative grid import values | The data may use the wrong sign, contain an error, or mix imports and exports. | Check the column headings. Confirm how the supplier records imports and exports and whether they appear in separate files. |
| Sudden changes that don’t match the rest of the year | The business may have changed its hours, added equipment, closed part of the site, or replaced the meter. | Check what happened on those dates, including closures, staffing changes, new equipment, and meter work. |
| Estimated readings | The supplier may have filled a gap without using actual meter data, making the usage pattern less reliable. | Check whether actual readings are available. If not, mark the estimated periods and explain how they may affect the results. |
| A meter replacement during the year | Data from before and after the change may use different formats, units, or starting points. | Find the replacement date and compare the readings on either side. Check whether either set needs adjusting. |
| Values recorded in a different unit | Some data may use watts, kW, or kWh, making consumption appear too high or too low. | Check the headings and supplier notes. Convert all values into the same unit before analysing them. |
Once you’ve fixed any problems, use the half-hourly meter data to see when the site uses the most and least electricity.
3. Confirm what the meter measures
The meter at the grid connection may not show all the electricity used at the site, especially if solar panels are already installed.
For example, a site may need 100 kW to run. If its solar panels provide 30 kW, it only needs to take 70 kW from the grid.
The meter data will show a net grid import of 70 kW. However, the site’s actual gross load, or gross site demand, is still 100 kW.
If you use the 70 kW net grid import as the gross site demand, you’ll wrongly assume the site needs less electricity during the day than it really does.
To work out the actual gross load, add the solar generation for each half hour to the grid import recorded during the same period. You will need the gross site demand to choose the right size solar and battery system.
If the site has more than one MPAN, check what each one covers and collect the readings for all of them so your analysis includes the whole site.
4. Plot the electricity-use pattern
Create several of the following charts to reveal different patterns in the data and build a clearer picture of how the site uses electricity.
Here are four useful charts you can plot:
| Chart | What it shows | What to look for | What it could mean for the project |
|---|---|---|---|
| Typical daily profile | How much electricity the site uses at different times on a normal day. | When the site opens and closes, when machines start, when electricity use is highest, and how much is used in the evening. | High daytime use may mean the site can use more solar power. High evening use may make a battery more useful. Short, sharp peaks may mean the battery needs to release power quickly. |
| Weekday and weekend profiles | How electricity use changes between working days and weekends. | Different opening hours, lower weekend use, and equipment that stays on when the site is closed. | Low weekend use may mean some solar power cannot be used straight away. High weekend use may show that equipment has been left on or needs to run all the time. |
| Seasonal pattern | How electricity use changes during the year. | Higher use in winter, more air conditioning in summer, busy seasons, and holiday closures. | Big changes during the year may affect the best size for the solar panels and battery. They may also save more money in some seasons than others. |
| Demand heatmap | Electricity use for every day and every half-hour, shown using lighter and darker colours. | Busy times that keep happening, unusual days, electricity used overnight, and short periods of very high use. | Regular peaks may give the battery a chance to reduce high demand. Short peaks may need a powerful battery, while longer periods of high use may need a battery that stores more energy. |
Use the charts together to understand when demand is highest, how long it stays high, and how often the same pattern returns. This will help you choose solar panels and batteries that suit how the site actually uses electricity.
5. Add information about the business
The readings show you when the site used electricity, but you should always ask the customer for the reasons behind the patterns you spot.
For example, ask about their:
- Normal operating hours: What time does the site open and close and does it use much electricity before staff arrive or after they leave?
- Planned shutdowns: Does the business close for holidays, maintenance, or part of the year?
- Day and night shifts: Does the site run one shift or keep working through the night?
- EV charging: Does the business already charge electric vehicles? Does it plan to add more chargers?
- New machinery: Has the business added any large machines that use a lot of electricity?
- Heating and cooling: Does the site use electric heating, air conditioning, or heat pumps?
- Refrigeration: Do fridges, freezers, or cold rooms run all day and night?
- Weekend work: Does the business work on Saturdays or Sundays, or is the site normally closed?
- Staff numbers: Has the business hired more people, reduced its team, or changed how many shifts it runs?
Use the answers to work out whether the patterns are normal or just a one-off. This helps you avoid choosing the wrong size solar system or battery because of a holiday shutdown or a short-term rise in production.
6. Interpret the site’s demand pattern
Once you understand how the business operates, use the charts to study its baseload and peak demand.
Assess the baseload
Baseload is the lowest amount of electricity a site uses regularly. You will often see it overnight or when the site is closed.
Use the daily charts and heatmap to find this level. Then compare it with the customer’s opening hours and the equipment they need to keep running.
A steady baseload may be normal if the site has equipment such as:
- Fridges or freezers
- Servers
- Pumps
- Security systems
- Ventilation
- Machines that must stay on
However, high electricity use while the building is empty may mean that lights, heating, air conditioning, compressors, or machines have been left on when they are not needed.
If the baseload looks too high, point it out to the client. If they do not plan to lower it, use the current baseload when you plan the solar or battery setup.
Assess peak demand
Peak demand is the highest level of average power use recorded during a half-hour period.
Half-hourly data does not show the highest split-second spike. A machine may briefly use much more power than the half-hourly average suggests. Where short spikes matter, you may need maximum-demand data or readings taken more often.
Use the charts to check:
- Peak height: How high does average demand rise?
- Peak duration: How long does demand remain high?
- Peak frequency: How often does the same peak return?
Compare the highest half-hourly demand with the site’s grid connection limit.
If the figures are close, the customer may have little spare capacity for:
- EV chargers
- Heat pumps
- New machinery
- Electric heating
- Site expansion
Include any planned additions so the project reflects the customer’s future demand as well as its current use.
At this stage, record the height, length, and frequency of the peaks. You will use this information later when testing battery sizes and other ways of managing demand.
7. Add the customer’s electricity tariff
Collect the customer’s current electricity tariff and recent bills. Electricity may cost more at some times of the day than others. For example, using 100 kWh during an expensive peak period may cost much more than using the same amount overnight.
Match the tariff prices to the half-hourly meter data. This shows when the customer buys the most expensive electricity and where there may be chances to reduce the bill.
You can then work out when solar panels or a battery could save the most money. For example, a factory battery could charge overnight when electricity is cheaper and supply the site during more expensive daytime periods.
This information helps you choose the right system and give the customer a more accurate savings estimate.
Using half-hourly data to plan the right commercial solar and battery setup for your client
Once you understand when the site uses electricity, how the business works, and what it pays for power, you can start comparing solar and battery options.
The aim is not to choose the biggest system that will fit. It is to find the setup that meets the customer’s needs and delivers the business the best value for their money.
Match the load profile with the solar generation profile
The load profile shows how much electricity the site uses during each 30-minute period. To create it, plot each checked reading on a chart in the order it was recorded.
The solar generation profile estimates how much electricity the proposed solar system could produce during the same periods.
Solar proposal software can produce an estimate when it has the following data:
- The size of the solar array in kWp
- The site’s location
- The direction and angle of the panels
- Nearby shade
- The limits of the solar inverter
The software uses local sunlight and weather data to estimate how much electricity the system could produce throughout the day and year.
Compare the load profile with the solar generation profile. This shows:
| What the comparison shows | Why it matters |
|---|---|
| How much solar electricity the site could use straight away | This is solar self-consumption. It means the customer buys less electricity from its supplier, creating an avoided grid import. |
| How much electricity the site would still need from the grid | This is the remaining grid import. It shows how much of the site’s demand the solar system could not meet. |
| How much solar electricity would be left over | This is surplus solar. The site could export it, store it in a battery, or produce less if an export limit applies. |
This is why the time of day matters more than the yearly total alone.
For example, two factories may each use 500,000 kWh a year. One may use most of its electricity on sunny weekday afternoons. The other may use most of it at night and at weekends.
The first factory could use more solar electricity as it is produced. The second may have more surplus solar to store or export.
This can make a big difference to the savings. Avoiding a 20p grid import may be worth more than exporting the same amount of electricity for 6p.
Compare different solar system sizes
Don’t assume the largest solar system will give the customer the best value.
A larger solar array will usually produce more electricity. The site may use some of it straight away and export the rest to the grid. These grid exports may earn money and help cover the cost of the electricity the customer still buys from its supplier.
But extra panels also cost more. You need to check whether the extra savings and export income are worth the added cost.
Also check the site’s export limit. This may stop it from sending all its surplus solar to the grid.
Compare several solar system sizes. For each one, work out:
- How much electricity it could produce
- How much the site could use itself
- How much surplus solar it could export
- How much money it could save or earn
- How much the system would cost
The best size is the one where the extra savings and export income are worth more than the cost of adding the extra panels.
Use the half-hourly data to size the battery
Once you know when the site has surplus solar and when it still needs electricity from the grid, you can test different battery sizes. This helps you find the battery that could save the customer the most money.
The full setup is called a battery energy storage system, or BESS. It includes the battery, battery inverter, and controls needed to store and supply electricity.
Battery sizing depends on two main measurements:
- Battery power, measured in kW, is how quickly the battery can charge or supply electricity.
- Usable battery capacity, measured in kWh, is how much stored electricity the customer can use.
For example, suppose the customer wants to keep grid demand below 200 kW, but demand rises to 300 kW for one hour.
The BESS may need to supply the missing 100 kW for that hour. It may therefore need at least 100 kW of battery power and 100 kWh of usable battery capacity.
The final BESS may need to be larger because some electricity is lost when the battery charges and discharges. The customer may also want to keep some stored electricity as a reserve.
Use the half-hourly data to check what jobs the BESS needs to do:
| Battery job | What to check |
|---|---|
| Store surplus solar | Is there enough surplus solar to charge the battery, and will the site need that electricity later? |
| Peak shaving | How high are the demand peaks, how long do they last, and how often do they happen? |
| Load shifting | Can the battery charge during cheaper off-peak periods and discharge when electricity costs more? |
A large BESS may offer little extra value if the site rarely has surplus solar, has only small demand peaks, or pays similar peak and off-peak prices.
Once you know what jobs the BESS needs to do, check how much power and stored electricity it can provide in real use.
Allow for the battery’s real limits
The total battery capacity shown on a battery data sheet may be higher than the usable battery capacity available to the customer.
The battery inverter limits how quickly the BESS can charge and supply electricity. The energy management system, or EMS, controls when the battery charges, supplies the site, or keeps electricity stored.
You also need to allow for:
- State of charge: How full the battery is
- Minimum reserve: Electricity kept in the battery for backup or other needs
- Round-trip efficiency: Electricity lost when the battery charges and supplies the site
- Battery degradation: The storage capacity the battery loses as it gets older
- Import limit: The most power the site can take from the grid
- Export limit: The most power the site can send to the grid
These limits may mean the customer needs a larger BESS than your first calculation suggests.
Compare the full project options, such as solar only, a smaller solar system with a battery, and a larger solar system with a battery.
Choose the smallest setup that can meet the customer’s needs after allowing for these limits. It should also save or earn enough money to cover the extra equipment and installation costs.
Show the client what each option could achieve
Finish by presenting your findings in a clear half-hourly data analysis report. This helps the client compare the options and see which one may offer the best value.
Start by explaining:
- Which half-hourly meter data and MPANs you used
- Whether the readings contained any gaps or errors
- Any changes you made to the data
- The site’s baseload and peak demand
- The main times when the site uses electricity
- The customer’s electricity tariff
Then compare the options you tested. These might include a solar-only system and several solar-and-battery systems.
For each option, show:
- The proposed solar capacity
- The proposed battery power
- The proposed usable battery capacity
- Expected solar self-consumption
- Expected grid imports and grid exports
- Any expected reduction in peak demand
- Expected annual savings
- The installed cost
- The expected payback period
Explain which figures come directly from the customer’s meter readings and which are estimates produced by your model. This helps the client understand that the forecast is not a guaranteed result.
You should also carry out a sensitivity analysis. This shows what could happen if an important detail changes.
For example, test:
- A different electricity tariff
- Longer operating hours
- Lower export income
- A higher project cost
- Less usable battery capacity as the battery gets older
This helps the client see whether the project could still be worth the cost if the actual results are better or worse than expected.
Analyse commercial solar and battery projects with GridVolt
A full year contains 17,520 normal half-hourly periods. Comparing several solar system and battery sizes by hand can therefore take hours.
The free GridVolt simulator can do this work in seconds. It uses the customer’s real half-hourly meter data and electricity tariff, rather than average usage figures or a single blended electricity price.
You can quickly compare different:
- Solar system sizes
- Battery power and usable battery capacity
- Import limits and export limits
- Electricity tariffs and export rates
- Solar-only and solar-and-battery options
You can also change the figures during a client meeting. A finance director, CFO, or project manager can test different options and see how each change affects the project cost, savings, income, and payback period.
This gives them a project they understand and figures they can explain when they take the proposal back to the board.
The GridVolt simulator, Energy Manager, and GridTrade use the same underlying system. This means the quote can use the same control rules that would guide the live installation, rather than estimates from a separate sales calculator.
Upload the customer’s half-hourly meter data. Then enter the proposed solar system, BESS, electricity tariff, import limit, and export limit to compare the options before presenting your quote.
Fill in the form on the right or get in touch via our contact page for free access to the simulator, and ask us how we can brand it with your name and brand.
Half-hourly data analysis FAQs
Can you analyse half-hourly data in Excel?
Yes. Excel can sort the readings, find missing ones, work out demand, and turn the numbers into charts.
But testing lots of solar system and battery sizes takes much longer. You also need to include the electricity tariff, battery losses, and equipment limits. Specialist software can do this work much faster.
What should you do if readings are missing?
First, check the date. When the clocks move forward, that day has only 46 half-hourly periods instead of 48.
For other gaps, ask the electricity supplier for the missing readings. If you have to use an estimate, mark it clearly and explain that the final result may be less accurate.
How do you analyse a site that already has solar panels?
Collect the site’s solar generation, grid import, and grid export records.
The meter may only show the electricity the site took from the grid after the solar panels supplied some of its needs. You may need to add the solar electricity used on-site to the grid import to work out how much electricity the site really used.
Can annual electricity consumption be used to size a battery?
It can give you a rough idea, but it cannot tell you the right battery size.
You also need to know when the site uses electricity, how high its demand rises, how long the peaks last, and when it has surplus solar. This helps you choose the right battery power in kW and usable battery capacity in kWh.
Is half-hourly data detailed enough to size a commercial battery?
It is detailed enough to show the site’s normal electricity use, its main peaks, and how long those peaks last.
You must then allow for things such as the battery inverter, minimum reserve, electricity losses, battery degradation, import limit, and export limit before choosing the final battery size.
What is sensitivity analysis in a solar and battery proposal?
Sensitivity analysis means changing one estimate to see what happens.
For example, you could test a higher project cost, a lower export rate, a different electricity tariff, or less battery capacity in later years. This shows whether the project may still be worth doing if things do not go exactly as planned.