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Do solar panels work on cloudy days and in winter?

Let’s face it, the UK isn’t renowned for its year-round sunshine, is it? For this reason, many people assume this means solar panels aren’t worth considering as they believe they can only work if there is plenty of direct sunlight available, 365 days a year. However, we can assure you that this isn’t the case. Solar panels do work on cloudy days and this article explains why and how.

Photovoltaic solar panels (photo meaning ‘light’ and voltaic meaning ‘electricity’) work by absorbing solar energy (or ‘photons’ if you want to be precise) from the sunlight spectrum that we can see. When light hits the panel, a certain amount of it is absorbed. The energy from this absorbed light creates an electric charge which is then converted by your home solar system into the type of electric current that we use in our homes to power all our devices.

In short, solar panels can use direct or indirect sunlight to generate power, though they are most effective in direct sunlight. This means that solar panels will work even when the light is reflected or partially blocked by clouds. In fact, rain will help wash away any dirt or debris that has collected on the panels to keep them clean and working efficiently!

It is important to reinforce that, whilst solar panels do work in cloudy weather, they will not work as productively as on a sun-filled day without taking certain precautionary measures. There are a few simple additions we encourage people to consider when installing home solar panels. These will combat the challenges posed by less available sunlight during the winter, optimise the efficiency of the system, and get the best possible return on investment.

How to get the most from your solar panels during winter

The UK winter months not only bring the cold weather, but shorter daylight hours and plenty of cloud, rain, and snow too! These can all affect the productivity of solar panels. As experts in the solar panel trade, we can advise how best to prepare for the winter months by optimising the efficiency of your system. This will ensure you make the most of the sun’s energy when you can and can store any surplus energy for when your system isn’t operating at full whack.

Jake Syrocki, Director, explains the best two ways to get the most from your solar panels in winter:

Invest in a microinverter system

A solar inverter is one of the most important parts of any solar photovoltaic system because it is the component which converts the solar energy (DC) generated by the panel into the electricity we can use in our home (AC). But, when it comes to selecting an inverter for your system, there is no ‘one-size-fits-all’ tactic. The three main types of inverters are string inverters, microinverters, and DC power optimisers. You can read how string inverters and microinverters work here.

The downfall of a string inverter system is that they can only perform as well as the lowest performing panel. Therefore, if you have shade over a section of your panels (even a small section – the size of an A4 sheet of paper) – the energy output decreases across the entire system. This is because the whole system is connected and links up to one central inverter. The other downside to a string system is that it isn’t possible to track which of the panels is underperforming because the panels are all connected and cannot be tracked individually.

In a microinverter system, each panel can work independently as an individual unit. The panels are not connected, and each panel has its own microinverter attached to it. This means that if an individual panel fails or is hindered by shade or snow, only that individual panel is affected. The productivity and efficiency of other panels in the system won’t suffer.

Moreover, the Enphase microinverters that we recommend boast burst mode technology that increases power production and ensures the panel excels during low light conditions. The microinverter captures the available energy from a PV solar panel at low light levels and bursts this energy into the grid when enough energy is available for one or more full AC cycles. In essence, burst mode enables microinverters to wake up early in the morning and stay awake until late evening; they begin producing energy earlier in the morning and finish later in the evening than a conventional inverter system.

Equip your panels with power optimisers

Power optimisers are a bit of a hybrid between string inverters and microinverters. Like microinverters, a power optimiser is a small attachment for the back of each panel in a string system.   The main objective of these optimisers is to enable the maximum energy yield from individual panels and increase the overall output of the solar panel system.  

Similar to microinverters, individual panel monitoring helps identify defects or shading issues which the optimiser will bypass. The optimiser’s ability to side-step the panel that is not working at total capacity allows your system to operate to its full potential, regardless of shade or snow cover. Fear not, optimisers are extremely durable and, just like your solar panels, are designed to work in extreme weather conditions.

The sun is lower in the winter and, therefore, shade extends further. For this reason, more solar panels in your system are likely to be shaded in the wintertime. So, it is important to think about shading when choosing your system; areas that might not be shaded during the summer when the sun is higher in the sky may change come winter.

Add battery storage and force charge on an off peak rate

Adding battery storage to your system is one of the best decisions you will make. Without one of these solutions, any solar energy generated from your solar panels that you do not use immediately will be sent back to the grid. However, adding a battery to your home solar system will mean that the excess energy generated by your panels during sunny hours will be stored. It can then be used to offset energy that you use at night and at other times when your system isn’t operating at full capacity.

You can also ‘force charge’ the battery on an off-peak rate. A tariff that ensures a cheaper overnight rate for electricity can be used to optimise your system by ‘force charging’ the battery from the grid during the cheap rate period. During the winter when the sun is lower in the sky and the daylight is available for a shorter period, the amount of energy produced by solar panels will be minimal and surplus energy won’t be substantial. This surplus will charge the battery a little bit but not fully. It also gets dark earlier so anything stored in the battery during the day will likely be used up in the evening before you go to bed. A solar battery can be topped up with cheap rate electricity overnight and used the next day when the demands are higher.

Essentially, a solar battery can be force-charged on a cheap rate overnight, storing that cheap-rate energy for use during the next day. Once the sun comes out, the energy in the battery is extended by solar power and, at times, is recharged too.

For example, let’s assume you have a 10Kw battery and force charge it on an off-peak rate of 7.5p a unit instead of paying a standard rate of 30p a unit. It would cost you 75p a day rather than £3 a day. Force charging will save you a lot of money.

Other useful tips

  • Schedule your appliances. Schedule your washing machine and dishwasher to come on during off-peak hours if you’re force-charging your battery.
  • Reduce shade on your solar panels. If your panels are obstructed by fallen leaves, branches, or snow, they won’t be working as efficiently as they could. In winter, prune back any overhanging trees and clear away any debris.
  • Combine your solar panels with other green technologies. For example, if you have an EV, charge it up in the daytime when the sun is shining, or overnight if taking advantage of an off-peak electricity rate.

The winter gives you a shorter window where solar panels are generating electricity, so make the most of this time by using more electricity when light levels are greatest, investing in a solar battery and force charging it on an off-peak rate, or using microinverters or optimisers.

Solar panels can be installed any time of the year, and you will start seeing savings on your bill in the first month. The winter months are a great time to get home improvement projects underway and completed. If you would like more information on how solar panels can work for you and your home, please do not hesitate to contact our knowledgeable and friendly team.

Choose us for high-quality solar panel installation or electrical services. Getting started is as simple as contacting us on 020 8087 0216 or sending an email to enquiries@tarvenlimited.co.uk.