Solar, batteries and EV charging on a half-hourly site

Solar PV, battery storage and electric vehicle (EV) charging are increasingly common on commercial and industrial sites. Each one changes when you draw electricity from the grid, and on a half-hourly (HH) site that changes what you pay. This guide explains how each technology affects your HH profile and what to check on capacity, connections and contracts.

Key points

• Once solar or a battery is installed, your HH import meter shows net import, not total consumption.
• Solar reduces daytime imports but does little in the winter red band.
• Batteries can move imports out of the red band and help manage peak demand.
• EV charging can add large loads, often at the most expensive time of day.
• Generation and storage need DNO approval, and capacity limits apply to imports and exports.

Start with your half-hourly data

Your existing HH data is the best starting point for any of these projects. It shows your base load, daytime profile, evening peak and how close you come to your Agreed Supply Capacity (ASC). Sizing solar, storage or chargers without it means relying on generic estimates. A load profile analysis can set this out before you speak to installers.

After installation, remember that the import meter records net import from the grid. To see what the site actually consumes, you also need data from the generation meter, battery system or charger management platform. Without it, a fall in imports can be mistaken for an efficiency gain, and a rise in consumption can be hidden by solar output.

Solar PV: what it does to your profile

Solar generation peaks around the middle of the day and is far higher in summer than in winter. On an HH profile it shows up as a dip in imports during daylight hours. When the site uses less than the panels produce, the surplus is exported.

• Self-consumption. Solar electricity used on site avoids buying it at your full unit rate plus non-commodity charges. Export is usually paid at a lower rate, so systems sized to match daytime demand tend to make the most of their output.
• Red band. Winter DUoS red-band periods fall in the late afternoon and early evening, when solar output is low or nil, so solar alone does little for red-band costs in winter.
• Capacity. Solar does not reliably reduce peak demand, because a dull day can leave you drawing the full load from the grid. Do not reduce your ASC on the strength of solar alone.

Exporting electricity

Exports are measured separately, usually under their own export MPAN, and on larger sites they are recorded half-hourly. To be paid for what you export you need an arrangement in place, typically an export agreement with a supplier or a power purchase agreement. Check how export is metered, who it is registered with and how payments are calculated. Exports also count against any export limit in your DNO connection agreement.

Batteries: shifting energy in time

A battery lets you choose when you use energy. On an HH site the main uses are:

• Avoiding red-band imports by charging at green or amber times, or from surplus solar, and discharging during the red band.
• Peak shaving: discharging when demand approaches your ASC to reduce the risk of excess capacity charges.
• Storing solar that would otherwise be exported at a lower rate.

The value depends on your contract. Red-band avoidance shows up directly on a pass-through contract, while on a fixed all-inclusive price it may only be reflected when your profile is re-priced at renewal. Control settings matter as much as battery size: a battery that is empty when the red band starts will not help. Ask the installer how the control strategy uses your DNO's time bands, and check the result in your HH data after a few months.

EV charging: a new and often badly timed load

EV chargers, especially rapid chargers and fleet depots, can add a large load. Vehicles often return and plug in during the late afternoon, just as the red band begins, so uncontrolled charging can raise both red-band consumption and peak demand.

• Use smart charging or load management to spread charging into green and amber periods where vehicle schedules allow.
• Set a site-wide power limit so chargers reduce output as total demand approaches your ASC.
• Consider whether a battery could supply some charging at peak times.
• Sub-meter chargers so you can see their share of the bill and recharge it if needed.

Capacity and DNO connection considerations

Any of these projects can affect your connection. At a high level:

• Import capacity. New loads such as EV chargers may need a higher ASC, and an increase may require network reinforcement, which can take time and add cost.
• Export capacity. Solar and batteries that export need a connection that permits it. Many sites use an export limitation scheme to stay within an agreed level.
• DNO approval. Generation and storage must be notified to or approved by your DNO under Engineering Recommendation G98 or G99, depending on size. Installers normally handle the application, but timescales vary by area.

The first two digits of your MPAN core identify your DNO, or you can find your network operator online. Our guide to Agreed Supply Capacity explains how capacity charges work, and a capacity review can check whether your ASC still fits after installation.

Before and after you install: a checklist

1. Download 12 months of HH import data and note base load, daytime demand and red-band use.
2. Check your current ASC and highest half-hour demand.
3. Ask installers to size systems using your data, not a generic profile.
4. Confirm who will apply to the DNO and the expected timescale.
5. Arrange export metering and an export payment agreement before going live.
6. Make sure generation, battery and charger data is recorded so you can see true site consumption.
7. Tell your supplier or broker, as a changed profile can affect volume tolerances and pricing at renewal.

Get help with solar, batteries and EV charging

Whether you are planning a project or already have equipment in place, we can analyse your HH data, check your capacity and make sure your electricity contract suits your new profile.

Request a free quote or bill check or call 07565 147 170.