Welcome your guests in the evening and enjoy your back yard at night without paying any electrical bills. Plus, the lights stay on all night for security and you do not need an electrician, since the lights run on a photocell and turn on automatically each night.
The lights have minimal maintenance, and new technology offers more powerful batteries and brighter light. There are several options for bright spot lights to illuminate trees, but solar path lights typically give off about the equivalent in ‘lumens’ of a 10 to 45 watt bulb, and they typically run for about 11 hours each night. As technology continues to improve, some lamps may give off even more light and last longer. As a rule of thumb, one premium fixture is needed for every ten feet of pathway.
The cost of solar lights is about $10 - $40 each plus about $2.50 per battery with a life of 5 years. vs. traditional lights at about $15 each. So, you pay more, but you can save about 50 cents a day with a set of eight solar lights. The offset cost of 8 incandescent bulbs that are each 45 watts is 360 watts per hour. Over 11 hours from dusk 'till dawn, the total wattage is 3,960 or 3.9 kWh per day. At the average rate of $.12 per kWh, the cost is $.48 per day. Over the year, that adds up to around $170 of savings.
The ROI Calculation is based on using premium level $40 fixtures since the less expensive ones do not give off as high quality light (8 lights, 4 in the front and four in the back or any combination that is right for you). The calculation also factors in additional wire, additional batteries after five years, and a consideration to replace two of them if damaged by pets or branches.
Choose fixtures that have enough solar panels to generate the light that you need, and make sure that the photocell ‘eye’ is clear from any dirt or tree sap to activate the light in the evening.
For lighting up trees or spot lighting a façade you’ll need more power than localized solar can provide, so consider either low voltage lighting or line volt fixtures. The advantage of line voltage is that you save by not needing a transformer and you also save by being able to use LED lights.