Why Does My Home Still Use Grid Electricity When I Have Solar Panels?

Installing solar panels can significantly reduce the amount of electricity your home needs to draw from the grid. However, one question homeowners can have after installing solar is: Why am I still importing electricity from the grid when I have solar panels?

The simple answer is that your solar panels generate electricity according to the amount of available daylight, while your home uses electricity according to your lifestyle and energy demands. Those two things don't always happen at the same time.

Understanding how generation, consumption and battery storage work together can help you get more from your solar installation.

Solar Generation and Electricity Usage Don't Always Match

Solar PV panels convert daylight into electricity that can be used within your home.

When your panels are generating electricity, that energy can help supply appliances and other electrical loads operating at that time. However, the amount of solar electricity available continually changes throughout the day.

Your electricity demand changes too.

For example, your home may have relatively low electricity consumption during the middle of the day but much higher demand in the evening when cooking, lighting and other appliances are being used.

If your home requires more electricity than your solar system is providing at a particular moment, the additional electricity needs to come from another source – typically the grid or, where installed and available, a battery.

Why Do I Import Electricity at Night?

Solar PV panels require daylight to generate electricity, so they don't generate electricity at night.

Without battery storage, electricity required after solar generation has stopped will normally need to come from the grid.

A home battery changes how you can use your solar generation. Instead of allowing all surplus solar electricity to leave the property when generation exceeds demand, some of that energy can be stored and used later.

This can increase the amount of your own renewable electricity you use within the property.

However, installing a battery doesn't necessarily mean you'll never need grid electricity.

Why Can I Still Import Electricity with a Battery?

A battery has a finite amount of usable stored energy.

If the battery reaches its minimum permitted state of charge, or the household demand exceeds what the system can provide, the home can begin drawing electricity from the grid again.

How long stored energy lasts depends on several factors, including:

• How much energy was available to charge the battery
• Battery capacity and system configuration
• Household electricity consumption
• The timing of that consumption
• Larger electrical loads operating within the home

This is one reason battery storage should be considered as part of the wider home energy system rather than in isolation.

What About High-Power Appliances?

The amount of electricity your home uses isn't constant.

Some appliances and electrical equipment can create periods of much higher demand. Depending on the design and operating limits of your solar and battery system, solar generation or stored battery energy may not always cover the property's full instantaneous demand.

Where demand exceeds the power available from the renewable energy system, electricity can be imported from the grid to make up the difference.

This doesn't necessarily indicate that something is wrong with the solar installation. It can simply be the energy system responding to the property's demand at that moment.

Why Do I Import More Electricity in Winter?

Solar panels continue generating electricity during winter and on cloudy days. They don't require hot weather to work.

However, UK solar generation is generally lower during winter because days are shorter, cloudier conditions are more common and sunlight is less intense.

That means there can be less solar electricity available both to power the home directly and to charge a battery.

As a result, a household that imports very little grid electricity during periods of strong summer generation may rely on the grid considerably more during winter.

Does Exporting Electricity Mean I Shouldn't Be Importing Any?

It's possible for a home to export solar electricity during one part of the day and import electricity later.

For example, your panels might generate more electricity than your home can use or store around the middle of the day. That surplus can be exported.

Later that evening, solar generation falls or stops while household electricity consumption continues. If there isn't enough stored energy available, the home then imports electricity.

Export and import therefore need to be considered across the complete daily energy profile rather than as contradictory events.

Can I Reduce How Much Electricity I Import?

The right approach depends on your individual system and how you use electricity.

One option is to move flexible electricity consumption towards periods when your panels are producing more power. Where practical, appliances such as washing machines and dishwashers can be operated during periods of solar generation rather than later in the evening.

Battery storage can also allow surplus daytime generation to be stored for later use.

The important point, however, is that the solar array, inverter, battery and household consumption all form part of the same energy system.

Simply adding more equipment isn't automatically the best answer. The system needs to be designed around the property's actual energy requirements.

Understanding Your Home's Energy Profile

Every property is different.

Roof orientation, shading, available roof space, household electricity consumption and when that electricity is consumed can all influence the performance of a solar installation.

Monitoring can provide useful insight into when your home is generating, consuming, storing, exporting and importing electricity.

Rather than focusing solely on whether the property ever imports electricity, it can be more useful to understand how much of your overall electricity requirement is being met by your renewable energy system and whether that system is operating as designed.

Getting More from Your Solar Energy System

A well-designed renewable energy system should take account of how your household actually uses electricity.

AGD Renewables provides solar PV and battery storage solutions designed around individual properties and their energy requirements.

If you're considering solar panels, battery storage or want to understand the options available for your home, speak to the AGD Renewables team.

Contact AGD Renewables to discuss a renewable energy solution for your property.

Call: 028 3886 8553 or email: info@agd-renewables.com