Protecting rooftop solar in storms and the monsoon

The hardest weeks of the year for a rooftop solar system in Tricity are not the monsoon rains but the storms that come before them. Late May and June bring dust storms and sudden squalls with strong gusts, then lightning, then weeks of heavy rain. A well-built system rides through all of it. This guide covers what to check before the season, what to do after a storm, and what to expect from output in the rains.

Before the season: the structure

Wind is the biggest risk. A raised array is a large flat surface held well above the roof, and a gust that gets underneath it pulls upwards on every leg and anchor. Before June:

• Check the bolts. Structure and panel clamp bolts can work loose over a year of heat and wind. They should be checked and tightened by a technician.
• Check the anchors and footings. Look for cracks around concrete footings and gaps around anchors in the slab.
• Look for rust, especially at cut ends, drilled holes and where the legs meet the footings.
• Clear anything loose from the roof: sheets, plastic chairs, old cans and branches can be blown into the panels.

The structure should have been designed for the local wind speed under IS 875 (Part 3). If you are not sure yours was, ask your installer. Our guide to raised, low and canopy structures explains how height and tilt affect the wind load.

Before the season: lightning and earthing

Lightning is common in Tricity’s pre-monsoon and monsoon storms, and the solar array is usually the highest point on the house.

• Earthing. The earth connections should be checked, and the earth resistance measured. It should stay low, and MNRE’s specification sets no more than 5 ohms.
• The lightning arrester should be firmly fixed, higher than the panels, and connected to its own earth.
• Surge protection in the DC and AC boxes should be checked. Many surge devices show a coloured window when they need replacing.

Before the season: water

• Protection boxes. The DC and AC boxes should be sealed, with cable entries closed, so that driving rain cannot get in.
• Cables. They should run in conduit or trays, clipped clear of the roof surface, and never lie where water collects.
• Drains. Make sure the roof drains near the structure are clear, so water does not pool around the footings.
• Leaks. Any point where the structure is anchored through the waterproofing should be sealed. A leak found in July is much harder to fix than one found in May.

A June health check covers all of this. It is one of the four seasonal visits in the 4-Year Care Shield included with our home systems.

During a storm

Stay off the roof. On-grid systems need no action from you. If the power goes off, the inverter disconnects automatically and reconnects when the supply returns. Do not try to switch off the DC side of the system in a storm.

After a storm

From the roof, in daylight and once the storm has passed, look for:

• Panels that have shifted, or clamps that have moved
• Cracked glass or a dent from flying debris
• Cables pulled loose or hanging
• Branches, sheets or debris on or under the panels
• Water inside the protection boxes

Then check the app. If output on the next sunny day is well below the day before the storm, or the inverter shows an error, call your installer. Do not touch a damaged panel or cable. Panels produce voltage whenever there is daylight, even when the grid is off.

Storm, lightning and flood damage is not covered by the manufacturers’ warranties, so photograph any damage for your insurer. Our guide to solar warranties explains what is covered.

Hail

Panels are built to withstand hail. Certified panels are tested by firing ice balls at the glass, and ordinary hailstones rarely break them. Large hail can still crack glass, so check after a hailstorm. A cracked panel should be replaced, because moisture gets into the cells.

What the monsoon does to output

Output falls in July and August, when cloud cover is heaviest. In Tricity, each kW typically makes about 100 to 125 units a month in July and August, against 130 to 160 in May. The rain also washes the panels, which helps. Our guide to why solar produces less has the typical figures for every month.

Net metering smooths the dip. Units banked in the bright spring months are carried forward and set against the monsoon months within the settlement year, as our guide to net metering in Punjab explains.

After the monsoon

The rains leave a film of silt on the panels as they end, and humid air can start rust. A clean and a check for rust and loose bolts in October gets the system ready for the winter months. Our guide to maintenance through the year sets out the full calendar.

Common questions

Can rooftop solar panels survive a storm?

Yes, if the structure is designed for the local wind load and properly anchored, and the bolts are checked each year. Most storm damage comes from loose bolts, weak anchoring or debris blown into the panels, which a pre-monsoon check helps prevent.

Do solar panels attract lightning?

No more than any other tall object on a roof, but the array is usually the highest point on the house, so a lightning arrester with its own earthing and surge protection in the DC and AC boxes are essential. Check them before the monsoon each year.

Do solar panels work in the rain?

Yes, but at much lower output under heavy cloud. In Tricity, July and August typically produce about 100 to 125 units per kW, compared with 130 to 160 in May. Net metering carries forward spring surplus to cover the dip.

Should I switch off my solar system during a storm?

No. An on-grid system disconnects automatically if the power goes off and reconnects when it returns. Stay off the roof during the storm and check the system in daylight afterwards.