How long does a commercial battery installation take? The G99 timeline explained

Ask most people how long it takes to install a commercial battery and they picture the crane: a container arrives, it is lifted into place, it is wired in, done. That part is real, and it is quick — one to six weeks on site for a behind-the-meter system. But it is not what sets the timeline. The programme for almost every commercial battery storage installation is set by the Distribution Network Operator, and specifically by the G99 connection process.

The physical install is the short part

For a typical behind-the-meter system — say a 250 kW / 500 kWh peak-shaver or a containerised 1 MW / 2 MWh unit — the on-site work runs to a few weeks: groundworks and hardstanding for a container (or room preparation for an indoor cabinet), cable routes, the crane lift or cabinet installation, terminations into your switchgear, and commissioning. Even a large containerised system is usually installed in under six weeks once everything is on site and the connection is agreed.

The catch is in that last clause: once the connection is agreed.

Why the DNO sets the real timeline

Any storage system above 16 A per phase — which is essentially every commercial battery — needs a G99 connection agreement with your DNO. The DNO reviews the proposed connection, may require a network study, and sets the protection and metering requirements. Because network capacity is limited in many parts of the UK, that study and the resulting connection offer are usually the single longest item on the programme. A G99 process can run anywhere from three months to eighteen months depending on where you are and how constrained the local network is.

This is the number that catches businesses out. The battery quote says “installed in weeks”; the reality is that you cannot energise it until the DNO says yes. An installer who only talks about the crane, and not the connection, is not showing you the real programme.

How to compress the timeline

You cannot make the DNO move faster, but you can start the clock earlier and avoid adding to it:

• Submit G99 at survey. The most effective single lever is to lodge the G99 application at the feasibility stage, not after the design is signed off. This runs the DNO study in parallel with your internal approvals rather than after them.
• Use a G100 limitation scheme where the network is constrained. A G100 export/import limitation scheme holds your site within its existing agreed capacity, which frequently lets a project proceed without waiting for a network reinforcement. This is often the difference between connecting this year and joining an eighteen-month reinforcement queue.
• Settle the fire and siting strategy early. Fire-authority and insurer sign-off can also add time if left late. We settle separation, detection and access at feasibility so they are not a surprise near go-live.

A realistic programme

For a behind-the-meter commercial install, a realistic end-to-end programme looks like: feasibility survey and G99 submission in weeks one and two; the DNO study and connection offer over the following months (the variable bit); fire siting and design freeze in parallel; then a one-to-six-week install and a witnessed commissioning once the connection is agreed. Grid-scale standalone projects are a different order entirely — eighteen months to several years, including full planning.

The honest version

A good installer will hand you a programme with the DNO milestone marked plainly as the critical path, and will tell you the realistic range for your specific network rather than quoting only the install weeks. If you want that for your site, send your half-hourly data for a free feasibility and we will give you an honest timeline — including where a containerised install or an indoor cabinet fits your site, and what your local DNO connection is likely to take.