Trees and Shade That Lower Your Energy Bills: Where to Plant and What It Saves

Shade is the slowest energy upgrade there is. A tree planted this fall won’t shade your roof for years. It’s also one of the cheapest, and it keeps working for decades without a filter change or a service call. The trick is putting the right tree in the right spot, because a tree on the wrong side of the house can raise your heating bill.

Where to plant for cooling

In summer the sun rises in the northeast, climbs high over the south at midday and sets in the northwest. That shapes where shade pays off.

• West side: the most valuable spot. Low afternoon sun hits west walls and windows during the hottest part of the day, and roof overhangs don’t block it.
• East side: worth shading for morning sun on bedrooms and kitchens, though mornings are cooler.
• South side: the midday sun is high, so overhangs and tall trees close to the house do the work. Use deciduous trees here only.

Plant medium trees about 10 to 20 feet from the house and large ones 20 or more feet out, so roots stay clear of the foundation and branches clear of the roof. Check the mature height and spread on the plant tag and plan for that, not the sapling.

Deciduous or evergreen

Deciduous trees, which drop their leaves in fall, are the right choice on the south, east and west. They block summer sun and let winter sun warm the house. Bare branches still cast some shade, so choose trees with an open winter form, and avoid a dense evergreen on the south side, where it would block free winter heat for decades.

Evergreens belong on the north and northwest, where cold winter winds usually come from in much of the country. A windbreak of dense conifers and shrubs, planted at a distance of two to five times the trees’ mature height, slows the wind hitting the house and cuts the cold air that leaks in. That matters most on the Plains, in the upper Midwest and on open rural lots.

Shade the AC, but don’t crowd it

An outdoor condenser sitting in full afternoon sun works harder. Shading it with a tall shrub, a small tree or a lattice screen can improve its efficiency, by up to about 10 percent according to the Department of Energy. The unit still needs air: most manufacturers ask for roughly 2 feet of clearance on the sides and 5 feet above, so check your manual. Shade from a tree canopy overhead is better than a hedge hugging the unit, and keep leaves and clippings off the coil.

Vines and trellises for faster results

A trellis or pergola on a west or south wall can be covered in two or three seasons, long before a tree is big enough. Use a freestanding trellis set 6 to 12 inches from the siding so air moves behind it and the vine doesn’t hold moisture against the wall. Deciduous vines such as grapes, hops or native coral honeysuckle drop their leaves in winter, which is what you want on a sunny wall. Avoid English ivy, which is invasive in many states and clings to siding and mortar.

What trees cost and how fast they grow

Smaller trees often catch up with big transplants within a few years, because they lose fewer roots when moved and settle in faster. A moderate-to-fast-growing species adds 2 feet or more a year once established. Very fast growers such as silver maple and Bradford pear tend to be weak-wooded and drop limbs, so most extension services steer homeowners toward sturdier native trees for your region.

1. 1

   Call 811 first 5 min · free

   The national call-before-you-dig line marks buried gas, power and water lines a few days before you plant.

2. 2

   Check overhead lines 5 min · free

   Don’t plant anything that grows over 25 feet tall under power lines.

3. 3

   Dig wide, not deep 1 hour · free

   Make the hole two to three times as wide as the root ball and no deeper. The root flare should sit at or slightly above ground level.

4. 4

   Mulch a ring 15 min · $0–$10

   Spread 2 to 3 inches of wood chips in a 3-foot circle, kept a few inches off the trunk.

5. 5

   Water deeply 10 min a week · free

   Give 10 to 15 gallons a week in dry weather for the first two summers.

What it adds up to

Take a house in a hot-summer state using 2,000 to 3,000 kWh a year on central air. Once two or three trees shade the west and south walls, cooling use might fall 10 to 25 percent, which is $35 to $130 a year at 17.5 cents per kWh. Add a windbreak in a cold, windy region and the heating saving can be larger. Against $100 to $300 in trees, and allowing for the years before they cast real shade, that pays back in roughly 5 to 15 years and keeps paying for 40 years or more, with cooler outdoor space as a bonus.