THE DIRECT saving comes from reducing electricity bought from the grid. Where tenants hold their own supply contracts, the benefit will depend on the lease and metering arrangement. On multi-let sites or properties with landlord-controlled services, owners may also have shared loads that can use electricity generated on site.

How Daytime Solar Cuts Electricity Bought From the Grid

On-site solar has the clearest effect on grid purchases where a building’s demand overlaps with the hours when the panels are generating. A warehouse operating throughout the working day might be running lighting, ventilation, conveyors, office equipment, refrigeration or other electrical systems while rooftop panels are generating power.

Electricity produced and used on site replaces some of the power that would otherwise be purchased from an energy supplier. The amount saved depends on the building’s consumption profile, system size, tariffs and how much generation can be used at the time it is produced.

This is why commercial solar installations are normally designed around the property rather than roof area alone. Going Green Renewables, which installs renewable energy systems across Surrey, Hampshire and Berkshire, states that it assesses the site and energy consumption before recommending solar panels and batteries. Its commercial solar work includes offices, retail parks, warehouses, factories and other business premises. Businesses can also consider how they will use or store excess electricity from solar panels, particularly when generation is higher than on-site demand.

For rental property owners, the same principle applies across a portfolio. A unit with steady daytime demand may use a high proportion of its solar generation immediately, while a lightly occupied warehouse could produce a larger surplus around the middle of the day.

How Battery Storage Reduces Grid Use After Solar Generation Drops

Solar production and electricity demand do not always follow exactly the same pattern. A building might produce more power than it needs at midday, then draw more heavily from the grid later in the afternoon or evening.

Battery storage provides a way to hold part of that unused generation for later, while other sites may have enough daytime demand to use more of the power as it is produced. At that stage, the decision is about how the site can use its surplus rather than how much electricity the array produces overall.

Battery storage does not reduce the building’s underlying demand. Instead, it changes when stored solar generation is available and can reduce grid purchases later in the day. Energy generated earlier in the day can be used after solar output has fallen, reducing the need to buy the same amount of electricity from the grid at that point.

Battery storage will not suit every building. The case depends on how much surplus is available, when the building’s demand rises again, the size of the battery and the electricity tariff. A property that already consumes most of its solar generation during the day may have less unused power available to store.

How Surplus Solar Can Lower EV Charging and Shared Service Costs

Battery storage is not the only way to make use of surplus generation. Some commercial properties have enough demand flexibility to move certain loads towards periods when on-site generation is stronger, particularly where those loads do not need to run at a fixed time.

EV charging is one example. Where vehicles are parked at a warehouse or industrial estate during the day, compatible charging equipment can use available solar generation rather than exporting all of the surplus immediately.

For multi-let properties, there may also be landlord-controlled electricity demand outside individual tenant units. Common-area lighting, security equipment, external lighting and shared charging infrastructure all create potential loads, although the actual arrangement will depend on the site’s metering and leases.

The running-cost benefit comes from using on-site generation for loads that would otherwise draw electricity from the grid. Owners therefore need to know which loads they control and when those loads operate before deciding where surplus solar energy should go.

How Exporting Surplus Solar Can Offset Energy Costs

Even a well-planned system can produce electricity that the building cannot use or store. In those periods, exporting power to the grid provides another route for gaining value from the installation.

The Smart Export Guarantee allows eligible small-scale generators in Great Britain to receive payment from SEG licensees for electricity exported to the grid. Solar PV installations can qualify where the scheme requirements are met and the total installed capacity does not exceed 5 MW. The tariff rate and contract terms are set by the chosen SEG supplier.

Export income should therefore be treated differently from direct on-site savings. Using solar electricity inside the building reduces grid purchases, while export arrangements pay for electricity the property does not need at that time.

For landlords, the export metering arrangements and responsibility for the SEG application need to be clear before expected income is included in the financial case. Eligible generators apply separately to a SEG licensee, which does not have to be the property’s existing electricity supplier.

How Matching System Size to Demand Improves On-Site Solar Savings

A large warehouse roof creates room for a substantial solar array, but installing the maximum number of panels is not automatically the lowest-cost option. The useful capacity depends on the building’s electricity demand, available export capacity and whether batteries or other daytime loads will absorb surplus generation.

Consumption data gives owners a stronger basis for sizing the system. Where half-hourly consumption data is available, it can show when demand rises and how much electricity the building uses during daylight hours, giving installers a clearer consumption profile to compare with expected solar output.

This also explains why two similar rental units may need different solar upgrades. A temperature-controlled warehouse operating around the clock has a different demand profile from a storage unit with limited equipment and shorter opening hours. The roof area may look similar while the economics of the solar system differ considerably.

For rental property owners, cutting running costs with solar depends on how closely the installation matches the way each building uses power. One property may consume most of its generation during working hours, while another has enough midday surplus to justify storage, EV charging or an export arrangement. Checking those patterns before the system is specified gives owners a clearer basis for deciding what equipment the property needs.