Solar photovoltaic (PV) panels convert energy from sunlight into electricity. They can be a great way to save money and contribute to a clean energy system. But because the sun doesn’t always shine when we need to use electricity, you’ll need to think about a few things to make the most of your solar panels: 

• Understanding how solar panels generate electricity.
• Behaviour changes you can make to get the most out of your solar panels. 
• Technologies that can maximise the benefits of your solar panels. 

Understanding how solar panels generate electricity

Solar panels don’t produce energy when you need it the most

On a typical sunny day, your solar panels will produce the most electricity in the middle of the day – from around 11am to 3pm. We refer to this as ‘peak energy generation’.  

But when you think about your daily routine, it’s likely this is not the time you typically use the most energy – your ‘peak energy use’. Energy use usually spikes in the morning – showering, putting the kettle on, making toast etc. Energy consumption during the day may be low – if it’s bright outside, there may be little need for lights and if people are out at work or school, appliances won’t be in use other than devices on standby and the fridge-freezer which cycles on and off. Between 4-8pm is when electricity consumption is at its peak. That’s because typically people cook dinner, watch TV, and often put on the dishwasher, washing machine or tumble drier during this time. 

So, there’s a mismatch between when solar PV is producing lots of energy and when we need it the most. 

Exporting unused electricity from solar PV panels to the grid 

You can get paid for exporting electricity you don’t use to the grid through export tariffs that some suppliers are obliged to offer. The mismatch between peak generation and peak use means that lots of people with solar panels end up exporting lots of the electricity generated by their panels to the grid and importing electricity from the grid to use in their homes. However, the amount you get paid for exported electricity can be lower than the cost of purchasing grid electricity. The rates for exported electricity vary between suppliers, so it’s a good idea to shop around. Some suppliers pay higher export rates if you also buy your electricity from them. You can compare export rates by looking at price comparison websites like The Eco Experts. 

So, to make the most of your solar panels it’s usually best to find ways to use as much of the electricity you produce as possible, by shifting your electricity consumption to sunlight hours or storing your solar-generated energy for later use. 

Behaviour changes to get the most out of your solar panels

Shifting your energy use

One way to make the most of your solar panels is to shift your electricity consumption to times when your panels are producing energy. Could you run your dishwasher or washing machine during the daytime? You should also make sure that when you run larger appliances, you’re doing so efficiently. Such as making sure you have a full washing load, so you need to do fewer washes. 

There’s a variety of technologies which can help you schedule when appliances run to make the most of times of high electricity generation. 

Staggering when you use high-wattage appliances

You can also stagger when you use appliances that require a lot of energy to make sure they use the free electricity produced by your PV and avoid needing to import more from the grid. For example, you can wait for your washing machine to finish its cycle before running the dishwasher. 

To do this, it’s helpful to know how much electricity different appliances use. Here are some typical power ratings of common appliances: 

Appliance	Power consumption	Cost per hour (based on 27p per kWh, average unit price in November 2023)
LED light bulb	5W	0.13p
Fridge	100W	2.7p
Laptop	50W	1.35p
Microwave	750W	20.25p
Washing machine	2,500W (2.5kW)	67.5p

Let’s assume your solar panels are generating a steady 1000W (1kW). Of this, 100W will be used by the fridge, which leaves 900W for other appliances. Based on the ratings above, you could use your 750W microwave for free and still have 150W available to run lower-power appliances, such as lights. You can’t run a 2500W washing machine with only 900W, so to run this at that time you would import the extra 1600W that you need from the grid. 

You can find out more about how much electricity different appliances use here. 

Technology to help you maximise the benefits of your solar panels 

Home solar PV setups differ from house to house. A basic system will have a number of solar panels forming an array, an inverter and a generation meter, and will then be connected to the grid via your consumer unit. The inverter may tell you how much the array is generating at the time (but not how much you are using in the home and how much you’re exporting). Inverters are also often installed in places which are inconvenient to access, such as the loft, making them difficult to use for solar generation monitoring. You might want to think about some of these options to track your consumption better: 

Solar energy monitors 

You can purchase monitors that track your electricity generation, consumption and export, which can help you understand how to make the most of your solar panels. The monitor will display this information via a smartphone app or a separate small display unit in the home. Solar energy monitors cost approximately £100-400 depending on the type. Some can be installed yourself but for others, you’ll need help from a qualified electrician. Any solar installation company should be able to help with this. 

Smart appliances and timers 

Most washing machines, tumble driers, dishwashers and water heating systems have timers which can be scheduled to switch on during hours when your solar panels are most likely to be generating. 

However, timers do not sense when your panels are actually generating electricity. They can only be set to come on during hours when it is likely that you will be generating electricity. If your washing machine is set to run at midday but it’s particularly overcast at that time, you may not be generating sufficient electricity to run the machine and may be drawing a portion of the energy used from the grid. 

Smart appliances are those with wi-fi connectivity and are part of what is known as the Internet of Things. This connectivity allows you to turn on appliances remotely when you see adequate solar generation. Smart plugs allow you to turn a socket on remotely in the same way, but this may be of limited use if you still need to turn the appliance itself on. 

Home Energy Management Systems (HEMS)

An optimal approach would be to automate when your appliances turn on and off using a Home Energy Management System (HEMS). This is a system that enables you to control and optimise all the smart technologies in your home from one platform, usually an app on your smartphone or tablet. 

You could set up your HEMS to automatically turn on particular appliances when solar generation is adequate. Some of these systems may require a particular inverter while others can be universally retrofitted.  

An important caveat is that an appliance with a long cycle, such as a washing machine, may start because there is enough PV generation, but it must then complete its cycle even if the PV generation is reduced (requiring you to import power from the grid). 

HEMS can also integrate EV chargers, heat pumps and PV diverters. For example, if you have solar PV, an electric battery, and an EV, you could use a HEMS to control when your battery and EV charge, and whether they charge from excess solar or from the grid. 

Diverters

PV diverters take any electricity generated by your solar panels which your household isn’t using and use it to power specific appliances in your home such as your immersion heater in your cylinder. They can also work with electric vehicle chargers and electric heating systems but are most commonly used to heat water).  

PV diverters are a great way to maximise your solar PV consumption, storing excess solar-generated electricity like a thermal battery or charging your car battery. With a typical PV array connected to an immersion heater, you should generate all the hot water you need during summer. As well as saving on fuel costs, this will also reduce usage of your boiler, prolonging its life and reducing your carbon footprint. 

PV diverters are easy to add to an existing PV system, taking less than an hour to fit. They cost around £250-500 to buy, or £600-800 with installation costs. And they can help you save around £100 a year on your bills. 

Batteries

Batteries store excess electricity generated by your PV system. This can then be used when the panels aren’t generating, either in the evening or the following morning. Domestic battery systems can store as much electricity as a household typically uses in a day, enabling a PV system to produce up to 70% of a household’s annual electricity demand. 

Some batteries can also provide electricity during a power cut. However, only the more expensive battery systems tend to have this function.

Batteries may not currently make financial sense for everyone. While a battery may save on imported electricity costs, the upfront cost of buying one remains high. However, as the price of batteries falls and electricity costs rise, their payback periods will reduce. There are also concerns surrounding the environmental impacts of battery production and disposal. 

The financial and environmental cases for domestic batteries are complex. If your primary motivation is to reduce your emissions, you would be better off focusing on reducing your heating demand and installing a heat pump. 

Heat pumps and PV

You can use PV to power a heat pump. This can sometimes be an effective combination, especially in terms of reducing your emissions. However, there are a few challenges when thinking about PV and heat pumps. 

Firstly, your PV system won’t be able to power your heat pump during nighttime as it won’t be generating electricity. A battery could help you get around this issue. 

Secondly, heat pumps use a lot of electricity. You’ll need a large array of solar panels to be able to power, for example, a 7kW heat pump in addition to your home’s other energy needs. 

Lastly, there’s a mismatch between the times of year when your PV system will produce the most electricity (summer) and when you need your heat pump most (winter). So, you’re likely to end up mostly powering your heat pump with imported electricity during the winter.  

PV generation could contribute to powering your heat pump through spring and autumn but won’t significantly reduce your heating costs in winter. You could also use your heat pump, powered by your PV system, to provide hot water through the summer months, but you could achieve this with a diverter for a fraction of the cost. 

PV, a heat pump and a diverter can work together, meaning your heat pump isn’t needed at all over the summer. However, the design, installation and commissioning of this kind of arrangement needs to be carefully considered.