Alectrona
Commercial guideWhere the local network cannot accept full export, a commercial array can connect with an agreed export limit under the ENA Engineering Recommendation G100, which caps what the site pushes to the grid while letting it self-consume freely.
OrientationThis is a plain-English orientation for a commercial buyer, not formal grid-connection advice; we confirm the export position that applies to your project.
When a commercial solar system connects to the grid, two separate questions get answered. The first is whether the generator can connect at all, which is settled through the connection application. The second is how much power the site is allowed to push back onto the network, the export limit. Where the local network is constrained, the Distribution Network Operator may not grant full export, and that is where export limitation comes in.
The framework that governs export limitation is the Energy Networks Association Engineering Recommendation G100. It allows a system to be set up so it never exports more than an agreed amount, or nothing at all, while the building continues to use as much of its own generation as it needs. For many commercial sites an agreed-limit or zero-export connection is a viable route rather than a compromise. This page is a plain-English orientation for a commercial buyer, not formal grid-connection advice. We confirm the position that applies to your project.
G100 is the ENA Engineering Recommendation that covers customer export limitation. It sets out how a generator can be constrained so that the power it sends back to the grid never exceeds an agreed figure, and how that constraint is implemented and demonstrated to the network operator. In practice the system is fitted with a G100-compliant export limitation scheme that monitors what the site is doing and throttles the inverters before the agreed limit would be breached.
The key idea is that limiting export does not limit what the building can use. The array can generate at full output and the site can self-consume all of it. The limitation only governs the surplus that would otherwise flow out to the network, holding it at or below the figure the DNO has agreed, or at zero where the offer is for a no-export connection.
It is worth keeping the two recommendations clearly apart, because they answer different questions. G99 is the connection application, the framework the DNO uses to assess and agree how a larger generator connects and exports safely. G100 is the export limitation recommendation, which governs how a system is constrained when the connection offer comes with an export cap.
The two meet in the connection offer. When the DNO assesses a G99 application on a constrained part of the network, it may offer a connection on the condition that export is limited to an agreed amount, or to zero. That export condition is then satisfied by a G100-compliant limitation scheme. In short, G99 sets the terms, and G100 is the mechanism that delivers an agreed or zero export limit where those terms require one.
Where the network is constrained, a G100 scheme can hold the site within the capacity already there. Both routes leave self-consumption untouched, so the building uses its own generation freely either way.
The system can export up to a set figure agreed with the DNO, and is held below it. Suits a site whose generation regularly exceeds its own demand and where even a modest export adds value.
Nothing is sent to the grid; the array serves on-site demand only. Often the simplest route to a fast offer on a heavily loaded part of the network, suiting a business that self-consumes nearly everything it generates anyway.
We model your half-hourly demand against generation before recommending a route, so the decision rests on your real load shape. This is orientation, not formal grid-connection advice; the export limit and conditions are set by the DNO for your connection.
On a healthy part of the network with spare capacity, the DNO can often grant full export and no limitation is needed. The case for G100 arises where the local network is already carrying a lot of generation and the operator will not accept unlimited export without network reinforcement, which can carry a real cost and lead time. Rather than wait on or pay for that reinforcement, the site connects with an agreed export limit instead.
For a business that self-consumes most of what its array generates, this usually fits the economics anyway. The value of a well-matched commercial system comes mainly from using the power on site to offset imported units, not from exporting, so capping export protects only a small surplus. An agreed-limit or zero-export design can make a connection viable, and faster, where a full export offer would stall the project.
The export strategy is part of the engineering work on a commercial project, not a setting changed at the end. The system design, the inverter selection, the protection settings and the export limitation scheme all feed the connection application, and the DNO's response can feed back into the design. We model your half-hourly consumption against generation for your roof first, so the export decision is made on your real numbers rather than guessed, then frame the connection route honestly.
The export limit figure, the response the scheme must achieve and any conditions are set by the network operator for your specific connection, so they are confirmed for your site rather than quoted generically. We specify the G100-compliant limitation scheme to the DNO's requirements and handle the technical correspondence as part of delivering the system. Treat this guide as orientation rather than formal advice; we confirm the position that applies to your project.
Underneath the recommendation sits a piece of control engineering. A G100-compliant scheme measures the net flow of power at the connection point, the boundary where the site meets the network, and compares it against the agreed export limit. When generation begins to push that flow above the limit, the scheme signals the inverters to back off, curtailing output just enough to hold export at or below the figure the network operator has set. The measurement, the decision and the curtailment happen continuously through the day as cloud cover, on-site load and array output all shift.
The detail that matters to a network operator is how quickly and reliably that loop responds. The Energy Networks Association sets out the design and performance expectations for these schemes, including how fast the limitation must act and how it should behave if a sensor, a communications link or a controller fails. A well-specified scheme is designed to fail safe, defaulting toward no export or a reduced output rather than continuing to push power onto a constrained network when it can no longer measure what it is doing. The protection settings themselves sit alongside the wider connection requirements in the ENA Engineering Recommendation G99, which governs how the generator connects and disconnects safely. We design the limitation around the real electrical layout of your site, because where the metering point sits and how the inverters are grouped both shape what the scheme has to do. The specifics are confirmed for your project rather than assumed from a template, and this remains orientation rather than formal connection advice. Our G99 application guide sets out the connection side that the limitation has to satisfy.
Once a network operator signals that full export is not available, there is usually more than one way forward, and the right one depends on the site rather than a general rule. An agreed export limit lets a measured surplus flow back, which suits a site whose generation regularly exceeds its own demand and where even a modest export adds value. A zero-export connection sends nothing to the network at all, which is often the simplest route to a fast offer on a heavily loaded part of the system, and it suits a business that self-consumes nearly everything it generates anyway.
Battery storage changes the arithmetic of that choice. A battery can absorb the midday surplus that a limitation scheme would otherwise have to curtail, then release it into the evening when the array has stopped producing but the site is still drawing power. On a zero-export or tightly capped connection, storing the surplus rather than throwing it away can recover energy that the export limit would have cost you, which is one reason the export strategy and the storage decision are taken together rather than in sequence. We model your half-hourly demand against generation before recommending a route, so the decision rests on your real load shape. The storage side is covered in our commercial battery storage hub and its cost considerations, while the value of any units you are able to export runs through export and SEG on the finance hub. Any figure attached to a stored or exported unit is modelled for your site, not promised, and depends on tariffs and metering that change over time.
It helps to understand what export limitation lets a project avoid. When a network operator cannot accept full export, the alternative to limiting the system is to reinforce the network so it can take the extra power. Reinforcement can mean upgrading cables, a transformer or a substation, and on the wider network it can reach back to higher-voltage infrastructure. That work carries a charge that can be significant, and a lead time measured in many months, sometimes longer where the constraint sits deep in the system. The rules that decide who pays for reinforcement, and how those charges are calculated, are set at industry level under the regulator Ofgem and applied by the network operator.
A G100 limitation scheme sidesteps that by holding the site within the capacity the network already has, so the connection can proceed without waiting on or paying for reinforcement. The trade is that a capped or zero-export design protects only the surplus the site would have exported, which on a well-matched commercial system is usually a small share of the value. The position is also bound up with where the project sits in the connection process, since a constrained network is often one with a busy connection queue. Our guides on the grid connection queue and on network charges explain those two pressures, and the role of the DNO guide sets out who is making these decisions on the local network, which for sites across Yorkshire and northern Lincolnshire is Northern Powergrid.
An export limitation scheme is only as good as the evidence that it works, so commissioning is a defined step rather than a formality. Before the connection is energised to its agreed terms, the scheme is tested to show that it holds export at or below the limit and responds within the time the network operator requires, including how it behaves when a measurement or communications path is interrupted. Depending on the connection, the network operator may witness that test or require documented results, and the recommendation framework set by the Energy Networks Association describes the demonstration the operator can ask for.
Compliance does not end at commissioning. The scheme has to keep doing its job through the life of the system, which means the metering, the controller and the communications between them all need to stay healthy. Changes on the site, such as adding capacity, altering the load or extending the array, can change the net flow at the connection point and may need the export arrangement to be revisited with the network operator. Because the limitation also depends on accurate measurement of what leaves the site, it sits close to the metering arrangements covered in our half-hourly metering guide. We specify the scheme, commission it to the operator's requirements and hand over the evidence as part of delivering the system, and the wider sequence is framed in our feasibility study guide. Treat this as orientation; the exact test, response time and witnessing requirements are confirmed for your connection.
The mechanism is worth understanding, because it explains why two similar roofs twenty miles apart get very different answers. Exported power pushes the voltage up at the point where it joins the network, and the further the site sits along a long, high-impedance overhead circuit from its primary substation, the more it pushes. Statutory limits on supply voltage are what stops it, not the size of the cable, so the ceiling arrives sooner at the end of a rural spur than on a unit a few miles from a primary.
Scale makes it concrete. A pole-mounted transformer serving one holding is a small piece of equipment, and an array above 50 kWp can exceed what it will pass long before the roof runs out of area. None of that is a judgement about the site. It is a property of the circuit the site is connected to, which is why the enquiry goes in before the layout is drawn rather than after it.
On an unconstrained site a south-facing array at a sensible pitch is normally right, because it makes the most units in the year. Under a low export cap the shape of the curve matters more than its total. A south array produces a tall midday peak, and on a capped site the top of that peak is thrown away. Splitting the array east and west produces a wider, lower curve that starts earlier, finishes later and sits under the ceiling for far more hours of the day.
On a shallow-pitch farm or warehouse roof the east-west option frequently delivers more usable energy than the south one, despite generating less in total. The same reasoning makes a higher ratio of panel capacity to inverter capacity worth testing, since the clipping that would be a real loss on an unconstrained site costs very little on a capped one. Both are modelled against your half-hourly data rather than defaulted, because on a capped site the largest annual figure is often not the one you get paid for.
Split east and west so the curve sits under the ceiling for more hours, and raise the ratio of panel capacity to inverter capacity. No extra equipment, and on a capped site it usually recovers more than adding modules would.
A battery sized against the surplus, or a flexible load moved into the generating hours. Grain drying, cold-store pull-down, water heating, pumping and vehicle charging all have some freedom about when they run. Loads tied to an operation do not, and separating the two on your own data is the first analysis.
The network can sometimes offer a flexible or curtailable connection instead of reinforcement. It energises sooner and costs less at the outset, in exchange for the operator being able to reduce export at times of constraint. Whether that is a fair trade depends on how much you were going to export in the first place.
Sometimes the right answer is genuinely a smaller array than you hoped for. A smaller array that is fully used is still a good asset, and that is better said at feasibility than after the offer arrives.
The binding figures on a capped site are the site's own daytime demand and whatever export the network will accept. Adding those two together gives the largest array that earns from every unit it makes. Anything above that line only earns its place if something absorbs it.
A battery is therefore sized against the surplus rather than against the array. Take twelve months of half-hourly consumption, subtract the modelled generation half hour by half hour, and the remainder is the profile the battery has to hold. On most sites the extreme case is a summer weekend when the plant is shut, generation is at its highest and there is almost nothing on site to take it. Sizing to that day gives a battery that is idle for most of the year, so the honest answer usually sits well below it. Load shifting is often the cheaper half of the same job, and it does the work of a battery with no equipment at all.
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They answer different questions. G99 is the connection application, the ENA Engineering Recommendation the Distribution Network Operator uses to assess and agree how a larger generator connects and exports safely. G100 is the related recommendation for export limitation, which governs how a system is constrained when the connection comes with an export cap. G99 sets the terms; G100 is the mechanism that delivers an agreed or zero export limit where those terms require one.
No. Export limitation only governs the surplus that would otherwise flow out to the grid. The array can generate at full output and the site can self-consume all of it. A G100-compliant scheme throttles the inverters before the agreed export limit would be breached, so what the building uses on site is unaffected.
Where the local network is already carrying a lot of generation, the operator may not accept unlimited export without reinforcing the cables, a transformer or a substation, which carries a cost and a lead time. Offering a connection on the condition that export is limited to an agreed amount, or to zero, lets the system connect without that reinforcement. It is often the practical route where full export would otherwise stall or be unavailable.
Usually very little, because the savings on a well-matched commercial system come mainly from using the power on site to offset imported units rather than from exporting. An exported unit is typically worth less than the unit you would otherwise buy. Where a system self-consumes most of its generation, an agreed or zero export limit protects only a small surplus. We model your half-hourly load first so the export decision is made on your real numbers.
Yes. The export strategy is part of the engineering work. We specify a G100-compliant limitation scheme to the DNO's requirements, feed it into the connection application alongside the design and protection settings, and handle the technical correspondence with the network operator. The export limit figure and any conditions are set by the DNO for your connection, so we confirm them for your specific site.
We do not quote a fixed price, because the cost of a G100 scheme depends on the site: how many inverters it has to control, where the metering point sits, the response the network operator requires and whether storage is added to recover capped surplus. It is one line within the wider system rather than a separate product, so we set it out in a surveyed proposal for your project. For how commercial pricing is built up overall, see our commercial solar cost guide.
The limitation scheme itself is specified and commissioned as part of the system build, so on its own it adds little to the programme. The timing that matters is the connection process around it, since the export terms come from the network operator and any witnessing or testing they require sits on their timescale rather than ours. A capped or zero-export route is often chosen precisely because it is faster than waiting on network reinforcement. We confirm the realistic timeline for your connection during feasibility; see our grid connection queue guide for what drives it.
Last updated June 2026
A guide can only take you so far. The figure you get is modelled from your own half-hourly load and a system sized from the on-site drone survey. No obligation, and systems this size sit outside the domestic MCS scheme, so the assurance is the engineering stack.