More industrial companies now look at battery storage, either to cut peak demand charges, to make better use of their own solar plant, or to keep critical processes running during outages. The idea is simple. The design behind it is not. A storage system that is sized wrongly or connected badly can sit idle for years and never repay its cost. This article walks through how a battery energy storage system (BESS) is designed, in the order the work is done, and what affects the timeline.
Stage 1: Define what the system must do
Everything else follows from the goal, so it comes first. The most common goals for a business are:
- Peak shaving: reducing the highest short-term demand to lower capacity or demand charges.
- Self-consumption: storing surplus solar energy during the day and using it in the evening.
- Backup power: keeping selected loads running during a grid outage.
- Energy trading or grid services: using the battery to earn from price differences or system services, where the market rules allow it.
One system can serve more than one goal, but each added goal changes the size, the control strategy and the economics. It is better to rank them than to try to do everything.
Stage 2: Collect data and analyse the load
A storage system is only as good as the data behind it. For an existing site we ask for at least twelve months of electricity consumption, ideally at 15-minute intervals, the current tariff and the invoices, the single-line diagram, the grid connection capacity and, if there is a solar plant, its production data.
From this we build a load profile. It shows when demand peaks, how long the peaks last, how much energy is used at night and how the plant behaves across seasons. A battery sized from the monthly total alone will almost always be wrong.
Stage 3: Size the system
Two numbers define a battery: power (kW or MW), which is how fast it can charge or discharge, and energy (kWh or MWh), which is how much it can store. The ratio between them gives the duration, for example one or two hours at full power.
Sizing has to take into account:
- usable capacity, because batteries are not discharged completely;
- round-trip efficiency, since some energy is lost in each cycle;
- degradation, because capacity declines over the years and the system must still meet its goal near the end of its life;
- the available connection capacity and space on site.
Oversizing wastes money. Undersizing means the system misses its target on the peak days that matter most.
Stage 4: Choose the technology and architecture
For stationary storage, lithium iron phosphate (LFP) cells are widely used because of their safety profile and cycle life, though the right choice depends on the project. The design then fixes the architecture: AC or DC coupling with a solar plant, the number and rating of the inverters (power conversion system), the transformer, protection and metering, and the energy management system that decides when to charge and discharge.
The control strategy is a design decision, not an afterthought. It determines whether the battery really delivers the savings calculated on paper.
Stage 5: Grid connection and permits
A storage system that cannot be connected is worth nothing. The grid operator sets conditions for connection, and the project must comply with them and with the applicable permitting and technical rules. This stage often runs in parallel with the design and can be the longest part of the project, because it depends on third parties. Starting the conversation with the grid operator early is one of the simplest ways to avoid delays.
Stage 6: Safety, location and civil works
The design must answer practical questions. Where will the containers or cabinets stand, and what ground works do they need? How will they be ventilated and cooled? What fire detection and protection is required? How do people and vehicles reach the equipment, and how is it isolated for maintenance? Placing a battery in the wrong location can force costly changes later.
Stage 7: Documentation and procurement
The final design package includes the single-line diagram, layout drawings, equipment specifications, cable and protection calculations and the control concept. With a complete package, the owner can request comparable offers from suppliers and contractors, rather than comparing quotes built on different assumptions.
How long does it take?
Duration varies by project size and by how quickly data and approvals arrive. The ranges below are indicative for planning only.
| Stage | Indicative duration | Main dependency |
|---|---|---|
| Goals, data collection, load analysis | 2–4 weeks | How quickly the client provides data |
| Sizing and concept design | 2–4 weeks | Quality of the load data |
| Detailed design and documentation | 4–8 weeks | Project size and coordination |
| Grid connection and permits | Several weeks to several months | Grid operator and authorities |
| Procurement and delivery | Depends on supplier lead times | Equipment availability |
The design itself is usually the shortest part. Approvals and equipment delivery often decide the final date.
Common mistakes to avoid
- Sizing from the monthly bill instead of the actual load profile.
- Ignoring degradation over the life of the system.
- Choosing equipment before the goal and the grid conditions are clear.
- Leaving fire safety and layout to the last moment.
- Treating the energy management strategy as a software detail.
How we can help
Remaks-Stal designs energy storage systems for industrial and commercial sites, together with solar plant design and the electrical engineering around them. We start from your consumption data and your goals, and deliver a design package you can use to obtain offers and to apply for connection.
If you are considering storage, send us the site location, the available roof or land area, your annual electricity consumption, details of your grid connection and what you want to achieve. We will come back with a clear next step.