Connecting Solar Panels to the Grid: The 3.68kW Line That Decides Everything

How connecting solar panels to the grid actually works

When you fit solar panels, you are adding a small power station to a network that was built to flow one way, from the grid to your home. So the local network operator needs to know about it. You never contact the National Grid or your energy supplier for this; you deal with your regional Distribution Network Operator (DNO), the company that owns the wires in your street.

There are two routes, and which one you are on is decided almost entirely by size. The dividing line is 3.68 kilowatts per phase (that is 16 amps per phase, on a normal single-phase home). At or below it, you are in the easy lane. Above it, you need permission first.

Check your connection route and rough export earnings

Tell the widget your system size and supply type. It shows whether you are on the simple G98 notify route or the G99 application route, whether export-limiting could keep you in G98, and a rough idea of yearly export earnings under the Smart Export Guarantee.

The belief that misleads buyers: "the export payment is the payback"

Sales conversations often dangle the Smart Export Guarantee as the reward: sell your spare power back, watch the cheque arrive. That framing quietly steers people wrong. Export rates are usually modest, and you only earn them on the power you do not use yourself. The bigger prize is hiding in plain sight: every unit your panels make that you use in the house is a unit you did not have to buy at the much higher import price. Self-consumption is worth far more per kWh than export.

Why most solar guides get the grid bit wrong

Most guides treat grid connection as a box-ticking afterthought and obsess over panel brands and payback charts. But the connection rules can change what you are even allowed to install. In a constrained area the DNO can cap your export or ask you to pay for reinforcement, turning a simple job into a slow, costly one. A guide that does not mention the 3.68kW-per-phase line, the G99 application or export limiting has skipped the part that actually decides your project.

The DNO application: when you must ask first

If your system is above 3.68kW per phase, your installer submits a DNO solar application under G99 before anything is switched on. The DNO checks whether the local network can absorb the extra power. In an area with spare capacity this is a formality of a few weeks. In a busy area, where lots of neighbours already have solar, it can come back with conditions: an export limit (a device that caps how much you can push back to the grid) or, in the worst case, a quote to reinforce the network, which you may have to part-fund.

This is the decentralisation strain in action: the local distribution network, not the national grid, is where rooftop solar piles up first. It is also why two identical homes a mile apart can get different answers.

Getting paid: the export MPAN and the Smart Export Guarantee

To be paid for export you need two things. First, an export MPAN, a meter point reference for power flowing out of your home, and a meter that can measure export (normally a smart meter in export mode). Without it, your exported power is handed to the grid for free. Second, a Smart Export Guarantee (SEG) tariff from a licensed supplier.

The SEG is the successor to the old Feed-in Tariff (closed to new applicants since 2019). The key difference: the government does not set the rate. Each supplier sets its own SEG rate, and they vary a lot. Importantly, you do not have to take your SEG from the same supplier you buy import power from, so it pays to shop the export rate on its own merits.

The insider insight: the 3.68kW line shapes the system you are sold

Here is the non-obvious move installers use. Because crossing 3.68kW per phase triggers the slower G99 application, many fit more panels than that but add an export limitation device set to 3.68kW. The panels can still generate freely for the house, only the power flowing back to the grid is capped. That keeps the job in the fast G98 "connect and notify" lane while letting you self-consume a bigger array. Since self-consumption is where the value is anyway, this is often the smart design, not a compromise.

Generation limit vs export limit are not the same thing An export limit caps only what leaves your home, not what your panels make or what you use indoors. So a 5kW array export-limited to 3.68kW still runs your home appliances and charges a battery at full output; it just throttles the surplus pushed to the grid. People often confuse the two and assume an export limit "wastes" their solar. It only caps the least valuable kWh, the exported ones.

What you should actually do

The bottom line

Connecting solar to the grid is governed by one threshold: 3.68kW per phase. Below it you connect under G98 and notify your DNO afterwards; above it you need a G99 application and the DNO's approval first, with the risk of export limits or reinforcement costs in busy areas. To be paid for export you need an export MPAN and a Smart Export Guarantee tariff, whose rate each supplier sets for itself. But the real value of solar is using your own power, not selling it, so design for self-consumption and treat the export cheque as the bonus it is.