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We take a good look at the Longi HiMo4’s efficiencies, performance and cost as we review the best solar panels in the UK.
The average home can save £1,190 every year with solar panels!
Longi Solar’s HiMo4 range of panels are some of the best solar panels available in the UK today. These solar panels are built using monocrystalline PERC half-cut cell technology – where the solar cells are cut in half, improving the solar module’s performance and durability. Along with several enhancements added, these panels can achieve up to 20.9% efficiency.
Longi HiMo4’s solar panels are available in 60-cell, 66-cell and 72-cell formats, built on gallium-doped silicon, which reduces light-induced degradation and increases performance.
The gallium-doped silicon solar panels are far superior to the regular P-type silicon modules often used by lower-end suppliers. The annual degradation of the Longi HiMo4 is 0.45%, whereas P-type solar panels will see annual degradation of 0.55%-07% per annum. This means that your Longi HiMo4 solar panels will only lose 11-13% of their power after 25 years, comparable to premium solar panels.
The power rating for the Longi HiMo4 is impressive at 350W-380W – especially in this price range. It comes with a 12-year product warranty and a 25-year performance warranty.
Overall, Longi performs much better than many other solar panels in the same price range and even competes with far more expensive models. The Longi HiMo4 offers good value for money and excellent performance.
The Longi HiMo series utilises high-efficiency PERC cell technology in both half-cut cells and bifacial modules. The bifacial modules are the most popular in-ground mount for commercial installations. The HiMo 4-range modules are available in 60-cell, 66-cell and 72-cell formats, built on gallium-doped silicon in order to increase performance and reduce the degradation of cells from 0.7% to 0.45% per annum. This means that your Longi HiMo4 will only lose 11-13% power after 25 years, comparable to more expensive N-type solar panels.
Highlights: Uses monocrystalline PERC gallium-doped silicon cells which are a good cost-effective alternative to more expensive N-cell solar panels.
Key benefit: 84.8% remaining power after 25 years, comparable to more expensive panels.
Warranty: There is a 12-year product guarantee as well as a 25-year performance guarantee available.
Cost: £100-£165 per panel, excluding the cost of installation and labour.
While the Longi HiMo4 isn’t the most expensive solar panel on the market, any investment in solar panels is quite significant for the average homeowner. It’s important to weigh the pros and cons carefully.
The benefits of the Longi HiMo4 include:
There are a few disadvantages to consider:
Longi uses smart soldering technology (Image credit: Longi)
Longi Solar, together with Shin-Etsu Chemical Co, started mass-producing new gallium-doped silicon cells in 2020 to combat the effects of light-induced degradation in P-type PERC silicon solar panels.
This form of light-induced degradation causes a 2-3% loss of power within the first few hundred hours of operation as oxygen is left over from the manufacturing process. Over the remaining life of the panel, losses drop depending on the quality of the crystalline silicon.
Many solar panel manufacturers use boron-doped P-type silicon wafers, which are less stable and more prone to light-induced degradation. Gallium-doped silicon reduces the damage significantly, retaining close to 85% of the original power rating after 25 years of use.
Longi Solar also uses “smart soldering technology”, using a triangular shaped micro busbar flattened at both ends. This reduces the inter-cell gap, increases the surface area and boosts efficiency.
The triangular segmented ribbon maximises the absorption of sunlight and boosts efficiency by 0.3%.
Longi doesn’t sell specific add-ons for the HiMo4, but several compatible add-ons can be purchased via your solar panel installer. Longi HiMo4’s standard solar kit comes with solar panels, micro inverters with monitoring tools and accessories, and racking materials.
Longi offers the HiMo3 panel, which is even more affordable than the HiMo4 model, but it’s much smaller and less powerful. It has a 10-year warranty and six busbars, as opposed to the eight busbars fitted to the HiMo4. The HiMo4 is larger, produces more power and comes with an additional two years in product warranty, which justifies paying a little bit more.
This table compares Longi HiMo4’s solar panel to some others on the market.
| Solar panel brand | Efficiency | Solar panel output | Warranty |
|---|---|---|---|
| Longi HiMo4 | 19.5%-21.0% | 350W-580W | 12 years |
| JA Solar JAM60S20 | 19.5% – 21% | 390W | 12 years |
| Project Solar Elite 400 | 20% | 400W | Lifetime |
The JA Solar’s JAM60S20 solar panel is quite similar to Longi HiMo4. Both panels offer a 12-year product warranty and a 25-year performance warranty and the same efficiency range. However, Longi HiMo4 solar panels are less expensive than JA Solar’s Jam60S20, and with similar features this is something to consider when choosing the right solar panels for your home.
Compared to Project Solar Elite 400 with a lifetime warranty, Longi HiMo4 falls short. However, the Longi HiMo4’s panel output range makes it a good choice of panel, especially if your household’s electricity consumption is high.
While the Longi HiMo4 is one of the most affordable solar panels on the market, its performance is on par with some of the more expensive modules in the UK.
| Name | Output | Cost per panel |
|---|---|---|
| Trina Solar TSM-DE06X | 365W | From £208 |
| Longi HiMo4 | 325W | From £107.40 |
| Panasonic HIT N 245W | 245W | From £250 |
The Longi HiMo4 doesn’t require a lot of maintenance. Regular rainfall should be more than adequate for keeping the solar panels clean. However, if you notice soiling or debris blocking the solar panels, you should rinse them from the ground with a regular garden hose.
If you cannot reach the solar panels with a hose, you can wipe the surface with a soft sponge or cloth and water. Do not use soap or chemical cleaning agents, and take care when climbing on the roof.
If performance doesn’t improve after cleaning, get in touch with a professional Longi technician.
“Longi Solar Panels are a great reliable option for a customer looking for an affordable mid-range panel from a company with a solid financial backing and reputation.”
“If you are considering Longi Solar panels, we recommend them, especially if you are looking for solar panels on a budget without sacrificing on efficiency. In addition to their value based price point, their modules are typically high-watt, which adds additional savings due to smaller bill of materials and installation costs.”
“Longi solar panels are tier one and so should be reliable, and I would not have a problem with installing them on my roof. They will also appeal to people who are interested in panels that should lose little in capacity over the years but don’t want the expense of purchasing premium panels. While many companies have run into financial difficulties after rapidly expanding, Longi’s financial position appears reasonably sound. While I don’t have any solid evidence, I suspect they will be around for a longi time. I can feel it in my gut. Specifically, my longi intestine.”
“Having had no issues from the previous panels, and with good reviews of the Longi panels, I am confident that they will perform well.
LATER: After one year in service, the panels are performing well and generating up to their maximum.”
“Once again, only on a two-week sample, but so far, they are working great. My panels are facing north, and even at 8 pm at night, it produces 3kw. I will rate again at a later time.”
“Although I had wanted to use LG panels, they were not easily available through Ahlec Solar, although I have been reassured these Longi 370 watt models should more than satisfy our needs for many years to come. Panels are producing plenty of power, and combined output for September was an impressive 1.266 MWh with June and July only just dipping under 1 MWh.”
“Having had no issues from the previous panels, and with good reviews of the Longi panels, I am confident that they will perform well.
LATER: After one year in service, the panels are performing well and generating up to their maximum.”
“Once again, only on a two-week sample, but so far, they are working great. My panels are facing north, and even at 8 pm at night, it produces 3kw. I will rate again at a later time.”
“Although I had wanted to use LG panels, they were not easily available through Ahlec Solar, although I have been reassured these Longi 370 watt models should more than satisfy our needs for many years to come. Panels are producing plenty of power, and combined output for September was an impressive 1.266 MWh with June and July only just dipping under 1 MWh.”
The cost of a solar panel in the UK, with a 300 W-rating, which is suitable for most households, is between £400 and £500. So, for the total solar system, typically a 4 kW install, the cost is around £6,500. The required roof space will be around 30m². A system with the ability to generate more energy will occupy a larger area of your roof.
If your system is powerful enough to deliver the amount of energy your household requires, it’s possible to take nothing from the National Grid, and exist solely on electricity generated by your solar panels. However, there are many variables to consider, such as the weather or an increased electrical demand, and it’s wise not to rule out the possibility of needing mains supplied energy.
Ideally, your household will run efficiently on freely generated electricity; however, there may be periods when all you’re using is a background load – when everyone’s at work, for example. In this situation, the power generated by your panels is being wasted, unless you add a solar battery to your system.
A battery ensures that no energy is wasted, but they can be quite pricey with the typical battery costing between £1,200 and £6,000 depending on its capacity. With an approximate life span of around 15 years before their storage capacity starts to decrease, you should figure on replacing the battery once during your panels’ lifetime.
Storage batteries are slowly coming down in price, and with the increased costs of energy, the return on your investment is happening sooner, making them well worth considering.
For the energy requirements of a typical UK household, a 4 kW system is ideal, and needs 16 panels that are 300 W-rated and take up around 30m² of roof space. If you are looking for a more powerful system, you’ll need a higher number of panels, taking up a larger area, or panels with the capacity to generate an increased amount of energy. For example, if you decide you need a 6 kW system, it might need 24 solar panels, and cover an area of about 43m².
Solar panels are one of the energy efficient home improvements that’s almost guaranteed to up the value of your property. The ability to reduce energy bills is an attractive prospect for any potential buyer, even if the output of your solar system may not suit a large family, there are plenty of purchasers whom it will suit. According to research from Zillow, solar panels can add around 4% to the value of your home.
Depending on your budget, roof size and region you live in, we recommend the Longi HiMo4 as the best all-round option, as well as the LG NeON H BiFacial, which has fantastic efficiency, and Panasonic HIT N 245W, which has great output and a compact size.
The time it takes you to break even from solar panels varies, but the average break-even time is around six to seven years. It used to take far longer to break even from solar panels investments, but luckily that time has decreased in recent years. Read our articles Are solar panels worth it – how solar panels pay back and Selling energy to the National Grid to find out more.
While compiling this review, we consulted hundreds of customer reviews, professional write-ups and recommendations, technical papers, and media articles related to the Longi HiMo4 to form our opinion. We created a scoring system (totalling 100 points) to rate the Longi HiMo4 against.
During our research, the total score was comprised of:
Read our guide to the best solar panels in the UK in 2022 or learn about how solar panels work. You can also find out if the economics add up for you in our guide which asks: are solar panels worth it?
