Home Solar Panel Installation: A Case Study

When Jo and Darrell Edgley moved from Britain to Durham, North Carolina, USA in 2006, they couldn't help but be impressed by the amount of sunshine as they searched for their new home. When they bought their house, the first thing Darrell said to Jo was: "We need to get solar panels".

Energy from the Sun

Jo and Darrell had always been interested in practical ways to use less energy in the home. As they started to investigate how to install solar panels, the first piece of advice they got was to measure how much and where direct sunlight falls on the house every day. Fortunately their roof faced directly south and was not shaded by trees, which is the best place to situate solar panels.

The roof has two slopes, one considerably steeper than the other. The installers recommended using the shallow roof to put the heavier PV [photovoltaic] panels on and the steeper roof for two thermal hot water panels. The Edgleys installed a 2.3 kilowatt photovoltaic system that will generate 2,280 watts, or 190 watts, from each of their twelve PV panels. Excess energy that they don't use is stored in the battery pack and any power left after the batteries are fully charged is fed into the local electricity grid. An energy monitor indicates how much AC load has been sent to the grid and the level of charge in the batteries. The Edgleys are reimbursed by a local 'green power' organisation for the power they supply to the grid.

Beating the Power Cut

In 2008, a power cut in Durham on the evening of July 4th, left the couple completely unaffected. Neighbours would comment months later: "That was your house with the lights still on". Jo and Darrell hadn't even noticed there had been a power cut!

Their 2.3 KW system is not quite enough to meet the total household energy requirements. The battery backup covers all the electrical items on the 'critical list': lights; fridge; freezer; microwave and the garage door opener. "A list which had to include the TV and computer!" notes Jo.

Hot Water

Installing PV solar panels is still quite an expensive option for most people. Depending on tax credits and overall energy usage, they can take many years to reap a return on the investment.

"It does depend on how you do the sums" says Jo "but that isn't the reason we installed them".

A much more affordable option is to install solar hot water panels. These are filled with glycol, or anti freeze, which is heated by the sun and used to heat water in a standard 80 gallon hot water tank. It passes through a coil heat-exchanger within the tank to heat the water but it never comes into contact with the water itself.

Darrell says: "There are only a few days in February when the water isn't really hot enough - a back up electric heater is used to supplement the weak wintry sun's rays. Solar hot water is a very practical way of reducing your heating bills by about 30%".

Sustainable Living

All that North Carolinian sunshine continues to impress the Edgleys. They do not have a clothes dryer and as Americans say, they 'line dry' all their clothes. They have looked into other reasonable ways to reduce energy consumption while maintaining a relatively comfortable lifestyle. Darrell has put energy monitors on a number of electrical items in the house and comments: "We were surprised how much energy was being drawn by computers and the TV while they were on standby or hibernating".

Darrell has put 'watt stoppers' on lamps, the TV and all the computers in the house. These are essentially motion detectors, if no one moves after a certain amount of time, they cut the power off. "It can be disconcerting if you are watching a film and the TV switches itself off" Jo says "it shows you how much of a couch potato you really are".

The Edgleys estimate that their utility bills are now around half the average for similar homes in the region. "In some months we actually sell more power than we buy and get credit for that". The batteries should last about 8-10 years and the solar panels will last about 25 years.

"We'll be looking to buy a whole roof made from solar tiles and they will hopefully be more affordable by then" says Darrell. "You could say we're mad. But we like to think we are pioneers, leading the way, hopefully encouraging others to think about ways to save energy one household at a time".

"OK we're a little bit mad" Jo concedes.