The same sun that warms the pavement could be harnessed to power much of your home’s electrical needs. Solar panels offer a fantastic return on investment and a fast payback period.
However, the thing with solar panels is that they can feel extremely complicated. Maybe words like ‘inverter’ or ‘kilowatt-peak’ make your eyes widen, and you think, ‘Maybe I should just leave it for now’.
Don’t worry. You’re not alone. And it’s why we at Electrical Innovations have put together this UK solar jargon-buster guide. Use these to stay on track when reading or listening about solar panels, and you’ll soon see why these energy- and cost-saving devices are well worth your investment.
Kilowatt (kW)
A watt is an electrical unit of measurement. It measures how quickly something generates or uses energy. A kilowatt just means 1,000 Watts. In the case of solar panels, a 400w panel might generate up to 400 watts at any given moment when the sun is shining on it around midday.
Now, the reality is that watts or kilowatts alone aren’t a very useful measurement. It’s much more helpful to know how much energy a system uses or produces over time, instead of just at any given moment. That’s where kilowatt-hours (kWh) come in (see below).
A home often uses between 0.2kW and 3kW at any moment, depending on what’s running. Kettles are the big ones, using about 2-3kW. Washing machines use around 1.5-2kW during the heating cycle. Phone chargers and individual light bulbs have much lower demand, typically between 5W and 20W.
Kilowatt-hour (kWh)
A kilowatt-hour shows how much energy a system produces or uses over time. Because of that, it’s a far more useful measurement, and it’s why your electricity bill charges you per kWh.
Your solar panels will measure how much energy they’re converting from sunlight. You can usually also see how much energy you’re consuming.
Kilowatt-peak (kWp)
Kilowatt-peak (kWp) indicates the maximum output of a single solar panel or a whole system under controlled test conditions.
These tests use fixed light levels and surface temperature. It isn’t necessarily 100% accurate in predicting how they’ll perform in real life. Still, it does provide a fair baseline for comparing one system with another. It also helps you judge output, match your solar panel setup to your peak electrical demand, and make sense of quotes.
Inverter
An inverter converts direct current from the solar panels into alternating current for your home to use.
Mains electricity is alternating current (AC), generated by power stations. Without going into it in depth here, alternating current reverses direction many times each second, so it moves easily through the network and into your home.
Solar panels generate direct current (DC). A battery’s output is also DC. This is electricity that flows in one steady direction at a constant rate without switching back and forth.
Basically, you need to convert the DC generated by the panels into AC before your home (or the grid) can accept and use it. And that’s the inverter’s job.
You can also use the inverter to track your panels’ performance. Most inverters come with mobile apps that show real-time and long-term performance, and these can be good ways to spot developing problems early.
Hybrid inverter
A hybrid inverter is one way you can pair your solar panels with battery storage in a DC-coupled system. It handles charging and discharging and manages power flow based on demand, time of day, and available energy from panels or your batteries.
These days, it can be a very sensible investment to pair your solar panels with a battery. This helps spread demand across the day and into the evening. But your system has to know when you want power from the panels, when it should come from the battery, and when to switch back to the mains supply. And, in DC-coupled systems, that’s the job of a hybrid inverter.
Micro-inverter
Micro-inverters sit under each panel and individually convert the output of each panel from DC to AC. It’s different from a standard inverter, which takes the combined DC output from all your panels and converts it to AC all at once.
Micro-inverters improve performance on roofs with mixed shading, varying angles or complex layouts, because if one panel underperforms, the others still operate at full capacity. Also, if you want to manage your system panel by panel, this is the best approach.
Smart Export Guarantee (SEG)
The Smart Export Guarantee (SEG) pays households for solar energy exported back to the grid. Your energy supplier sets their own rates, so rates vary widely across the market. Most sit at around 5-15p per kWh. In some cases, you might get up to 20p or 30p per kWh at peak times on time-of-use tariffs, provided you also use the supplier for your mains electricity.
The SEG scheme relies on smart meters, which record how many kWh you send back into the grid. Your payments typically come monthly or quarterly, depending on the provider and their tariff.
SEG replaced the older Feed-in Tariff (FiT).
Battery capacity
A battery’s capacity is the maximum amount of usable energy a battery can store. It’s measured in kilowatt-hours (kWh) – see above.
For example, a 10kWh battery stores up to 10kWh of usable energy. That is, enough energy to power your home at 1kW for 10 hours, or at 5kW for 2 hours, and so on.
In practice, a battery’s capacity might be slightly lower than the listed figure, depending on the model, its age and its depth-of-discharge settings.
A battery’s capacity impacts how you use your solar energy. A larger battery stores more solar energy from the day for use in the evening or overnight. Some homeowners also store off-peak grid energy overnight and use it during the following day.
Depth of discharge (DoD)
Depth of discharge shows how much energy you use from a battery before recharging it. A DoD of 80% means you use 80% of the stored energy before you have to recharge the battery. For example, the 10kWh battery mentioned above would have to recharge once you used 8kWh, and the remaining stored energy dropped to 2kWh.
Regularly going beyond this point can cause long-term damage to the battery. However, many modern batteries allow deeper discharge than 80%.
Understanding DoD helps you compare real-world capacity and how that affects your system. For example, you might find two batteries offering 10kWh, but if one has a DoD of 80% and the other of 90%, you might get better performance from the latter.
Cycle life
Cycle life tracks the number of full charge-and-discharge cycles a battery undergoes before its usable capacity falls below a set threshold. Basically, it shows the expected lifespan of the storage system. Manufacturers publish this figure.
Why is cycle life important to know about? Well, it helps you estimate long-term value, your payback period and ROI. If a battery offers thousands of cycles, it should support daily use over many years.
Solar yield
Solar yield describes the total amount of energy your system produces over time. Installers estimate your annual yield using MCS modelling (Microgeneration Certification Scheme), local climate data, and your roof’s position.
Yield gives you practical expectations, but it is an estimate. Seasonal yield peaks in late spring and summer in the UK; winter offers significantly reduced output, and some years are just sunnier than others.
String
A string is a group of solar panels wired together. Your inverter treats each string as one source.
Now, this is an effective way to reduce wiring complexity. However, mixed shading across the panels in a single string can reduce output across the entire string.
To make sure that doesn’t happen, installers design custom string layouts for your rooftop to avoid shading issues. In homes with complex roofs, micro-inverters or power optimisers are the most effective way to reduce losses.
Power optimiser
A power optimiser sits on each panel and actively monitors and adjusts its power output. It works alongside your inverter to improve your panels’ overall performance by reducing the impact of partial shading or panel mismatch.
You’ll also get panel- and string-level monitoring from power optimisers, so they can be an excellent investment, particularly if you live near large trees or other shade.
AC-coupled system
An AC-coupled system uses a separate battery inverter that links to the home’s AC wiring. Solar feeds the house through the main inverter, and the battery charges through the separate AC-coupled inverter.
This layout is often the simplest option if you’re adding battery storage to an existing solar system, and it gives you flexibility for future upgrades.
DC-coupled system
A DC-coupled system connects solar panels and batteries via a single hybrid inverter (mentioned above). The inverter directs energy into charging or household use without passing through a separate battery inverter.
DC-coupled systems have fewer ‘conversion’ steps. Since you always lose a little energy at these points (inverters, battery storage, battery discharge), a DC-coupled system tends to have higher overall efficiency than an AC-coupled system.
Solar diverter
A solar diverter directs excess solar energy into a hot-water cylinder. It senses when your solar system would automatically send energy back to the grid and instead redirects it to the immersion heater.
In other words, your home gets what feels like free hot water from surplus solar, especially during spring and summer. If you use a lot of hot water, such as taking long showers or relying on hydronic underfloor heating loops, solar diverters can reduce gas or electric hot-water costs and increase the value of daytime solar use.
Time-of-use tariff
Time-of-use tariffs offer lower rates for the electricity you use from the grid during off-peak hours and higher rates during peak hours.
These tariffs are the best option if you have or are thinking of getting a solar panel system, especially if you also have battery storage. You store cheap energy, use your own solar energy, send any surplus back to the grid and reduce peak daytime use.
As mentioned earlier, households with batteries can also charge them overnight (at a lower, off-peak rate) and power their homes using that stored energy during peak daytime periods.
MPPT (Maximum Power Point Tracking)
Inverters use MPPT algorithms to determine the optimal operating point for each panel string. These algorithms mean your inverter automatically adjusts voltage and current to match changing sunlight conditions.
Inverters need MPPT to maximise output throughout the day. It accounts for the sun moving through the sky, the clouds coming and going, and the shade from trees or buildings moving across the roof, with no manual input required. The result is that your system stays close to its maximum practical output for the conditions on the day.
Get trusted solar from Electrical Innovations
So, is solar jargon complex in the UK? At first glance, perhaps. But once you break it down, you’ll find there’s very little to feel overwhelmed about.
It’s essential to understand how solar works, so you can recognise the potential benefits of installing or upgrading a system at your home. At Electrical Innovations, we’re dedicated to helping homeowners in and around the Midlands make the most of modern energy-efficient installations, including solar panels and battery storage.
If you’re curious to see what solar panels can do for you and are looking for a trusted local solar installation expert, we’d love to hear from you. Get in touch for a commitment-free chat about your needs, and we’ll explain the best solar setup to match your lifestyle, budget and goals.
