Commercial Solar, Battery Storage and EV Charging: The Complete Integration Guide
Most businesses approach solar panels, battery storage, and EV charging as three separate decisions. In practice, they form a single integrated energy system — and businesses that plan them together achieve savings 30–50% greater than those who install them piecemeal. This guide explains how the three technologies interact, how to size each component for maximum benefit, and what a fully integrated commercial energy system looks like in practice.
Solar Panels
Generate free electricity during daylight hours. Reduce grid purchases by 30–60% for typical commercial operations.
Battery Storage
Store surplus solar for evening use. Enable peak shaving to reduce demand charges. Increase self-consumption to 80–95%.
EV Charging
Power your fleet and staff vehicles from solar. Reduce fuel costs by 80% for electric vehicles. Access Workplace Charging Scheme grants.
Why Integration Multiplies the Returns
A standalone commercial solar system generates electricity when the sun shines and exports any surplus to the grid at low Smart Export Guarantee rates (typically 5–8p/kWh). The business saves the difference between grid purchase price (22–28p/kWh) and SEG rate on electricity it self-consumes, and earns very little on electricity it exports.
Adding battery storage changes the economics fundamentally. Surplus solar generation that would otherwise be exported at 7p/kWh is stored in the battery and used in the evening at 25p/kWh — an immediate 18p/kWh improvement. Self-consumption rates that were 40–50% for a solar-only system reach 75–85% with battery storage, maximising the volume of generation captured at full retail rates.
Adding EV charging to the solar + battery system creates a third benefit: the electricity that previously had to be purchased from the grid (or was exported at low rates) is now used to charge company vehicles, saving the petrol/diesel equivalent fuel cost. For a business with 10 electric vans each driving 100 miles per day, solar-powered charging saves approximately £12,000–£18,000 per year in fuel costs, on top of the building energy savings.
The interactions compound: solar powers both the building and the chargers, battery storage ensures generation is available when chargers are needed, and smart energy management optimises the allocation between competing demands. The result is a system that consistently outperforms the sum of its parts.
Understanding Self-Consumption: The Key Metric
Self-consumption rate — the proportion of solar generation consumed on-site rather than exported — is the primary determinant of financial performance. Every percentage point of self-consumption adds value: 1% better self-consumption on a 100kW system generating 90,000 kWh per year adds 900 kWh consumed at £0.25 rather than exported at £0.07 — an extra £162 per year, or £3,240 over a 20-year system life.
| Configuration | Self-consumption | Annual saving (100kW) | vs. solar-only |
|---|---|---|---|
| Solar only (office) | 40–55% | £10,000–£14,000 | Baseline |
| Solar only (factory/DC) | 60–80% | £15,000–£20,000 | +50% |
| Solar + battery | 75–90% | £19,000–£24,000 | +90% |
| Solar + battery + EV | 85–98% | £22,000–£30,000+ | +120%+ |
Based on 100kW system generating 90,000 kWh/yr at 25p/kWh commercial rate and 7p/kWh export. EV savings are additive fuel cost replacement.
Battery Storage: Choosing the Right System
Commercial battery storage for solar-integrated applications falls into two main categories: DC-coupled systems (battery connects before the inverter) and AC-coupled systems (battery connects after). For new commercial solar installations, DC-coupled systems from manufacturers like GivEnergy, BYD, and CATL offer the highest round-trip efficiency (92–96%) and simplest installation. AC-coupled systems (including the Tesla Powerwall+) are better suited to retrofitting batteries to existing solar installations.
Sizing the Battery
Commercial battery sizing depends primarily on what you want to achieve:
- Self-consumption maximisation: Size the battery to store the expected daily solar surplus. A 100kW solar system with 40% self-consumption during generation hours produces approximately 54,000 kWh/year of surplus — averaged across 1,800 generation hours, that is 30kWh of surplus per generation day. A 50–100kWh battery captures most of this surplus for evening use.
- Peak shaving: Size the battery to cover your peak demand period. If your maximum demand charge is based on 30-minute periods between 4pm and 7pm when your peak consumption is 200kW, a 100kWh battery discharging at maximum power for 30 minutes covers the peak. Calculate your demand charges and the battery size needed to cap them below the demand charge threshold.
- EV charging buffer: If you need to charge multiple EVs simultaneously without grid reinforcement, size the battery to buffer the charging load. A 200kWh battery can supply 200kW of EV charging for 1 hour — enough to charge 28 EVs from 0-80% in 1 hour on 7kW chargers, all from stored solar.
EV Charging: From Workplace Scheme to Fleet Charging
Commercial EV charging for solar-integrated systems spans a wide range of use cases. The commercial EV charging infrastructure decision should be made alongside (or before) the solar system design.
Workplace Charging for Staff
The Workplace Charging Scheme (WCS) provides grants of £500 per charger socket, up to 40 sockets per applicant business, to cover the cost of purchase and installation of EV charge points. A business installing 20 dual-socket 7kW workplace chargers receives £20,000 in grant funding. Solar-powered workplace charging uses an energy management system to allocate available solar generation to chargers first, topping up from the grid only when solar is insufficient.
Fleet Depot Charging
For logistics and delivery businesses transitioning to electric fleets, depot charging is the primary use case. A depot charging 50 electric vans overnight (returning between 5pm and 8pm, departing by 7am) has different requirements from a business charging a small number of vehicles during the day.
Solar-powered depot charging works best with a combination of solar + battery: solar generates during the day, battery stores the generation, and the battery discharges into the chargers during the evening charging window. An energy management system can schedule charging to avoid peaks, prioritise certain vehicles for early departure, and automatically adjust based on grid tariff periods.
Smart Energy Management: The Brain of the System
The three-component system — solar, battery, EV charging — requires intelligent energy management to optimise between competing demands. Modern energy management systems (EMS) use real-time data, weather forecasting, and tariff signals to make second-by-second decisions about how to allocate available generation and battery capacity.
Key EMS functions for an integrated commercial system include:
- Solar forecasting: Day-ahead weather and irradiance forecasts allow the EMS to predict tomorrow's generation and plan battery charging and discharging accordingly.
- Demand response: The EMS can shed non-critical loads (EV charging, HVAC pre-heating) during grid demand peaks to reduce demand charges or support grid balancing.
- Tariff optimisation: With time-of-use tariffs, the EMS automatically charges the battery from cheap overnight electricity and discharges during expensive periods, independent of solar generation.
- EV smart charging: Vehicle departure times and minimum state of charge requirements allow the EMS to schedule charging to coincide with peak solar generation or cheap tariff periods.
- V2G (Vehicle-to-Grid): Next-generation systems allow EV batteries to discharge back into the building, providing a mobile energy storage resource. Currently limited in the UK by vehicle and charger availability, but commercially viable for fleet operators by 2027–2028.
The Complete Financial Picture: An Integrated Essex Business Case
Take a 15,000 sq ft office building in Chelmsford with 25 staff, 8 company electric cars, and 100kW solar + 100kWh battery + 8x 7kW EV chargers (AC coupled):
Investment
Annual savings
After the 3.2-year payback, the integrated system generates £33,200 per year in combined energy and fuel savings — with zero marginal cost for 20+ years. The total return over a 20-year system life exceeds £560,000 on a net investment of £106,500.
Our Integrated Energy Approach
EC Eco Energy designs and installs all three components — commercial solar, battery storage, and EV charging — from a single point of accountability. Our integrated design process considers all three systems together rather than independently, which means the solar system is correctly sized for future battery and EV charging additions, the inverter specification supports all three loads, and the energy management system is configured to optimise the whole.
We provide a single combined financial model showing the payback, IRR, and annual savings for the integrated system across all three components — making the investment decision clear and comparable.
Frequently Asked Questions
No. The most common approach is to install solar first, then add battery storage and EV charging as your needs evolve. Solar panels deliver positive returns from day one. Battery storage is most valuable once solar is installed, as it stores excess solar generation rather than exporting it at low rates. EV charging can be added to an existing solar system at any time, though sizing the solar system correctly for future EV load at the outset avoids the need for a grid reinforcement application later. We design all our systems to be expandable, with inverter capacity and cable sizing that accommodates future battery and EV additions.
The answer depends on how many vehicles you are charging and when. A 7kW AC charger for a van requires 7kW of generation at that moment — which a 10kW solar system can provide on a sunny day. For fleet charging, the calculation is more complex: a fleet of 20 electric vans each requiring 50kWh per day needs 1,000kWh of daily charging energy. A 200kW solar system generating 200kWh on a summer day provides 20% of that need — the rest comes from the grid or battery storage. Smart charging management — scheduling charging to coincide with peak solar generation — maximises the solar-to-EV transfer rate.
Peak shaving uses battery storage to reduce the maximum electricity demand drawn from the grid at any point. Many commercial electricity tariffs include a 'demand charge' based on your peak half-hourly consumption — which can represent 20-40% of your total bill. By discharging the battery during high-consumption peaks (loading bay operations, equipment start-up, peak production periods), you reduce the demand charge. For a business with high demand charges, battery storage pays for itself through demand charge reduction alone, independent of any solar generation benefit.
Time-of-use tariffs charge different rates at different times of day — typically higher in morning (7-9am) and evening (4-8pm) peak periods, and lower overnight (midnight-6am). A battery storage system can charge from cheap overnight electricity and discharge during expensive peak periods, creating an arbitrage benefit independent of solar. Combined with solar, the battery charges from solar during the day and discharges in the evening peak, maximising total savings. The best commercial TOU tariffs can create battery round-trip arbitrage of 10-15p/kWh, making a 100kWh battery worth an additional £4,000-£6,000 per year in tariff arbitrage alone.
Modern integrated energy systems use a single energy management platform that monitors and controls all three components — solar generation, battery state of charge, and EV charging loads. GivEnergy's cloud platform, for example, provides real-time visibility of generation, consumption, battery state, and EV charging on a single dashboard accessible via phone or computer. The system can be configured to automatically optimise charging and discharging based on electricity tariffs, weather forecasts, and scheduled vehicle departure times. Aggregated data supports Scope 2 emissions reporting for ESG and carbon accounting purposes.