Longi Hi-Mo 4 solar panels review

Known for their high efficiency and durability, Longi Solar’s Hi-MO 4 panels are among some of the best solar panels available. They utilise monocrystalline cell technology and achieve up to 20.9% efficiency, offering excellent performance. Available in several formats, the panels feature reduced light-induced degradation and have an annual degradation rate of just 0.45%. This means they retain 87%-89% of their power after 25 years, which is comparable to many premium models.

With a power rating of 350W-380W, a 12-year product warranty and a 25-year performance warranty, Longi Hi-MO 4 panels offer exceptional value, easily competing with more expensive options in the market.

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:

• Cost: Starting from as little as £107.40 per panel, Longi HiMo4 solar panels are very affordable, with good performance to match the solar panel cost. 
• Performance: Most solar panels priced at the lower end of the market guarantee about 80% power after 25 years, but Longi promises 84.8% power after 25 years. 
• Reputation: Longi is a Bloomberg 1-rated company and a participant in China’s Top Runner programme (a government solar panel scheme with the goal of boosting solar panel efficiencies). As a stable and trusted brand, they’ll be around for a long time. 
• Efficiency: With an efficiency of up to 20.9%, Longi is one of the most efficient lower-priced brands on the market. 

There are a few disadvantages to consider: 

• Introduction of N-type: Longi is introducing a next-generation N-type solar panel, which may replace the HiMo4 range in the near future.
• No UK office: Longi doesn’t have a local presence in the UK, which means that support is offloaded to third parties.

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 HiMo4 add-ons

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 Hi-MO 5m panel, which is even more affordable than the Hi-MO 4 model and has higher efficiency rates. It employs the same monocrystalline PERC, gallium-doped silicon cells to reduce panel degradation and has Longi’s smart soldering technology to boost efficiency, making it a great alternative to the Hi-MO 4 panel.

This table compares Longi HiMo4’s solar panel to some others on the market.

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.

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.