Home solar power: what to check before you install panels

Rooftop solar can reduce electricity bills for many years and make a home less dependent on the grid. In a sunny country like Sri Lanka it is an especially attractive option. But a solar system is a long-term investment, and the best results come from planning it properly before anything is installed.

These are the questions to answer first.

1. How much electricity do you use?

Start with your electricity bills. Collect at least twelve months if you can, because use changes through the year with fans, air conditioning and the number of people at home. Your monthly consumption in units (kilowatt-hours) is the basis for sizing a system.

Also think ahead. Are you planning to add air conditioning, an electric vehicle, a water pump or more people to the household? A system sized only for today may be too small in a few years.

2. Reduce waste first

The cheapest unit of electricity is the one you do not use. Before sizing a solar system, look for easy savings: LED lighting, efficient appliances, inverter air conditioners and turning off equipment left on standby. Reducing consumption first can mean a smaller, less expensive system.

3. Is your roof suitable?

A good solar roof has:

• Enough space without shade from trees, water tanks, neighbouring buildings or other parts of the roof. Even partial shade on some panels can reduce output significantly.
• Good orientation and angle. Close to the equator, panels perform well across a range of directions, but an installer should check how your roof faces and how much sun it receives during the day.
• Sound structure. The roof must carry the weight of panels and mounting frames safely and withstand strong winds. Old or damaged roofs should be repaired before installation, because removing panels later to fix the roof adds cost.

A qualified engineer should inspect the roof structure, not just the surface.

4. Which type of system?

There are three common types:

• Grid-connected (on-grid) systems work alongside the electricity grid. They usually have the lowest cost, but they normally switch off during a power cut for safety reasons.
• Off-grid systems use batteries and do not depend on the grid. They suit locations without a reliable grid connection, but batteries add significant cost and need replacing over time.
• Hybrid systems connect to the grid and also include batteries, so essential loads can keep running during outages.

The right choice depends on your budget, how reliable your grid supply is and what you need to keep running during a power cut.

5. Understand the grid connection rules

In Sri Lanka, connecting a rooftop system to the grid requires approval from your electricity provider, and there are different schemes for how the electricity you export is credited or paid for. The available schemes, tariffs and procedures change from time to time, so check the current rules with your provider, and make sure your installer handles the application and meets the technical requirements.

6. Choose quality equipment and installation

A solar system is only as good as its weakest part. Ask for:

• Panels and inverters from established manufacturers, with clear warranties
• Proper cable sizes, protection devices and earthing
• Mounting frames designed for your roof type and local wind conditions
• A clear quotation listing every component, the expected annual generation and the warranty terms

Be cautious of quotations that are much cheaper than others without a clear reason.

7. Plan for maintenance

Solar systems need little maintenance, but not none. Dust, leaves and bird droppings reduce output, so panels need occasional cleaning. Inverters need checking, and connections should be inspected periodically. Most modern inverters let you monitor generation on a phone, which makes it easy to notice when something is wrong.

8. Think in years, not months

Compare systems on total value over their lifetime, not just the initial price: expected generation, equipment life, warranties, maintenance and battery replacement if you have one. A slightly more expensive system that performs reliably for many years is often the better investment.

Get an engineer's view

SUM ENGINEERS designs and installs electrical systems, including solar, and can assess your roof, your consumption and the right system for your home. To talk about a solar project, contact us at hello@sum.lk.