How much battery storage does my commercial site need? An easy guide to Solar power storage
Battery storage varies by commercial site, so we conduct a site survey to assess several supporting factors. The correct amount of Solar power storage is always site-specific, and your battery storage capacity depends on your site’s average daily surplus solar generation (kWh) and your out-of-hours demand.
In this guide, we outline methods for commercial battery sizing, explain the terminology that underpins it, and consider the mistakes that cost businesses money in commercial solar system design.
Are you still unsure if BESS (battery energy storage system) is the right step for your business operations? Then, before you read this guide, read through our Battery Energy Storage page; it covers all aspects to help you determine if a battery storage system is the right step: https://excelenergy.co.uk/commercial-battery-storage-systems/.
Table of Contents
WHAT IS THE DIFFERENCE BETWEEN KWH AND KW, AND HOW DOES THIS DETERMINE YOUR COMMERCIAL SYSTEM?
The difference between kWh and kW is that Kilowatt-hour (kWh) measures energy capacity. It tells you how much electricity a battery can store and deliver over the course of a complete charge and discharge cycle. In simple terms, it represents the size of the battery’s energy store.
For example, a battery with a rated capacity of 100 kWh and a 90% depth of discharge (DoD) provides 90 kWh of usable energy. This is the portion of the battery’s stored energy that can be used to supply your site, including during periods when solar generation is no longer available.
A kilowatt (kW) measures power, in other words, how quickly a battery can supply electricity at a particular moment. While kWh describes how much energy a battery can store, kW describes how much power it can deliver at once.
For example, a battery with a continuous discharge rating of 50 kW can provide up to 50 kW of power at any given time. If your site reaches a peak demand of 80 kW, a 50-kW battery cannot cover the entire load. The remaining 30 kW would need to come from another source, such as the grid or solar generation.
A 100-kWh battery operating at a 25-kW discharge rate would take around 4 hours to fully discharge. Increase the discharge rate to 50 kW, and the same 100 kWh battery could discharge in around 2 hours. The energy capacity hasn’t changed – only the rate at which that energy can be delivered has increased.
HOW DO INSTALLERS DETERMINE HOW MUCH BATTERY STORAGE YOUR COMMERCIAL SITE NEEDS?
We size your system accurately using 3 important data points:
AVERAGE DAILY SURPLUS GENERATION (KWH)
AVERAGE OUT-OF-HOURS DEMAND (KWH)
PEAK DISCHARGE REQUIREMENT (KW)
We review the excess energy your solar panels produce that would usually return to the grid, the energy consumed when the solar array is inactive, and the maximum power surge your facility demands at any time.
TYPICAL LARGE SITE SIZING FOR A BESS
LARGE HOTEL OR A WAREHOUSE IN THE UK
Approximately 50 kWh
INDUSTRIAL & LARGE COMMERCIAL SITE IN THE UK
Approximately 100 kWh to MWh scale
CAN COMMERCIAL BATTERY STORAGE BE USED TO BUY AND SELL ELECTRICITY AT DIFFERENT TIMES?
Yes, commercial battery energy storage systems (BESS) can be used for energy arbitrage, where electricity is stored when prices are lower and discharged when electricity prices are higher. Where a business has a suitable electricity tariff and operating profile, the battery may be charged using surplus solar generation or, where appropriate, lower-cost off-peak grid electricity, before being discharged during higher-cost periods.
For example, if there is not enough solar generation available to fully charge the battery during the day, a suitable tariff could allow the battery to be topped up during cheaper overnight periods, such as between 10pm and 7am, and then used when electricity costs are higher. The potential value depends on the site’s electricity tariff, battery efficiency, available capacity, charging and discharge limits, and the difference between electricity prices at different times.
This means battery sizing should not be based solely on solar generation and out-of-hours demand. For some commercial sites, the potential for energy arbitrage, time-of-use tariffs and intelligent battery energy management should also be considered when assessing the appropriate BESS capacity and operating strategy.
Some BESS systems can also participate in wider flexibility and electricity markets, including the Balancing Mechanism and frequency response services, subject to eligibility, technical requirements and market arrangements. These opportunities mean that the value of a commercial battery can extend beyond simply storing surplus solar energy.
ARE YOU THINKING... “HOW CAN BATTERY STORAGE HELP MY BUSINESS?”
commercial battery storage system can help your business by reducing energy costs, improving energy resilience, boost sustainability, gaining more control over energy use, and supporting long-term cost stability.
REDUCED ENERGY COSTS
Storing electricity can help with your costs, especially during a period of high inflation. If you install a solar power storage system and use it when energy prices peak, it can give your business an advantage.
IMPROVING ENERGY RESILIENCE
Battery storage can provide additional support for the equipment and systems your business relies on. During short-term power interruptions, it can help maintain essential operations and provide an additional layer of energy security.
INCREASING THE USE OF CLEAN ENERGY
Battery storage can help businesses make greater use of locally generated electricity, particularly when paired with solar PV. Energy generated during the day can be stored and used later, helping businesses increase the amount of renewable energy they consume on site.
TAKING GREATER CONTROL OF ENERGY CONSUMPTION
Businesses are increasingly looking for ways to manage their energy use more effectively and reduce their exposure to periods of higher electricity costs.
IMPROVING LONG-TERM ENERGY COST STABILITY
Battery storage can contribute to this goal by enabling businesses to make better use of self-generated electricity and, where applicable, shift consumption towards periods when electricity is less expensive. This can help businesses take a more proactive approach to managing energy costs over the longer term.
SO...IS BATTERY STORAGE THE NEXT STEP FOR YOUR BUSINESS?
It could be, and if you’re unsure, you can complete our project enquiry form to speak to one of our renewable energy experts who can guide you: https://excelenergy.co.uk/project-enquiry/.
We approach solar power storage for our clients with a bespoke battery storage system so that it suits their business type and allows their site to rely on steady, affordable power.
Battery storage is becoming an increasingly practical option for small businesses looking to take greater control of their energy costs, strengthen resilience and support their sustainability goals. As technology develops and more solutions become available, businesses can use energy storage to manage demand more effectively and plan ahead with greater confidence.
Interested in finding out whether battery storage could benefit your business? Discover your options: https://excelenergy.co.uk/commercial-battery-storage-systems/