Keeping Your Cool in the Summer

Is it hot enough for you? It’s a challenge staying cool when the temperature rises, and especially

hard to do it without using a lot of electricity. We have been experiencing spikes of extra hot weather, even in February, which is making it hard to stay cool without using air conditioning. Whole house air conditioners are real energy hogs, using more energy than anything else in your home, but they do keep you comfortable when it’s broiling outside.

If a central air conditioning unit is run for 9 hours a day it can use between 3000 and 5000 watts of electricity per hour, which amounts to 30-40 Killowatt-hours of electricity per day. That will cost about $100 a month (at average kWh rates). Many people run their A/C for 16 or more hours a day, which would cost over $240 a month. Window units use less energy and cool a smaller space, but are still energy hogs compared to anything else in your home.

A reality check about air conditioning:

• The number of households that use air conditioning globally is expected to quadruple by 2050. If those estimates prove correct air conditioners alone would use as much electricity as the entire country of China does today.
• Three quarters of all U.S. households have air conditioning.
• Air conditioning accounts for over 16% of the total electricity in the U.S. used in the warm months.
• In this country alone we spend more than $29 billion per year on air conditioning. As a result, roughly 117 million metric tons of carbon dioxide are released into the air each year.
• On hotter days the A/C can be over 70% of your electric bill.
• Overnight temperatures in many cities rise by 2’F as AC units vent hot air outside of homes.

If we could all avoid using an air conditioner in the summer we could spend those billions of dollars on something else, and significantly reduce our contribution to greenhouse gas accumulation in the atmosphere.

So what are our options?

Do we really need air conditioning? First let’s look at some of the options for staying cool without using an air conditioner. There are lots of things you can do to use less energy and still stay cool.

Block the sunlight from coming in to the house. Direct sunlight coming in heats the air inside the house.

Light colored curtains or blinds will keep direct sunlight from coming in. Curtains work better than blinds because blinds let warm air flow from window to room. Open the curtains and the windows at night to let cooler air in. Opening windows on opposite sides of the house will create a cross breeze, cooling you even more. Plant shade trees in locations that will block sunlight from entering the home directly. Awnings can also help keep sunlight out.

It’s cheaper to cool yourself than to cool the whole house. Moving air cools you more than still air, so any kind of fan in a room where you are will help. When the hotter air from your body is moved away and replaced by cooler air you feel cooler. And if you are sweating, a fan also cools you through evaporation. Consider a ceiling fan, or a standing room fan, or put a little desk fan right where you are working, to keep air moving around you. While an air conditioner can use over 3000 watts, a floor fan uses only 100 watts even on highest speed. Ceiling fans use only 50-90 watts depending on its size, and costs about a penny per hour to run. Central A/C costs 70 times more. But turn the fan off when you leave the room – it doesn’t cool the air, it just cools you.

Some other cooling tips:

Replace any incandescent bulbs, which give off heat. Use LED’s instead. LED’s also use much less energy than incandescent bulbs.

Reduce cooking heat whenever possible.

A better insulated home can keep cool air in (and keep the heat in during cold months). Also doors and windows that are well-sealed will keep outdoor heat from getting in.

Light colored house paint and light colored roofs will reflect sunlight, while dark colors will absorb it.

If you are going to use an air conditioner there are some things to consider to help you use less energy. First, make sure you purchase an Energy Star unit, which will use 15% less energy, or even 30% less than older models. Look for the Energy Star label. And make sure the system you purchase is sized right for the space you need to cool. If you buy a unit that is over-sized, you are just wasting money because a smaller unit will cool your home just as well. Consult an energy auditor or your utility company (not an HVAC contractor) to figure out the right size unit for your home. Or calculate it your self: figure 20 BTU/square foot.

Once the system is running make sure to clean or replace the A/C filter every month, so that a clogged filter does not cause the unit to draw more electricity. Also, central A/C systems deliver the cool air into your rooms through a duct system, and if the ducts are leaking, you are losing a lot of the cooling benefit that you are paying for. Most homes with central A/C units have leaky ducts.

But do you really need the entire house to stay cool all day? Central A/C wastes a lot of energy if you don’t use all the rooms in your home every day. Consider getting a window unit instead, which can cool the room or rooms that you spend the most time in. Close rooms that you are not using to minimize the amount of space that needs to get cooled. A window unit uses about 6 times less energy than central air conditioning. You can save even a little more energy by turning on the “energy saver” function which turns off the fan when the unit shuts off.

Whether you are using a whole-house system or a window unit you can turn the temperature up a couple of degrees and that will use significantly less energy. Every degree F below 78’ uses up to 8% more energy. You probably won’t be significantly less comfortable if you run the air conditioner less often, or wait a few hours to turn it on. And be sure to turn the temperature up when you leave the house. You will not save energy by leaving it on when you are gone. Something else that will help: shade the window unit or condenser outside to use less energy, if possible, and don’t let it be blocked by branches or weeds which could restrict the air flow. For more information about air conditioners visit: https://www.energy.gov/articles/energy-saver-101-infographic-home-cooling .

There are a few other kinds of whole house cooling systems, including evaporative cooling systems (which work best in very dry climates), and Whole-House Fans, which use a large fan mounted in the ceiling to draw hot air up and out through the attic, creating a breeze.

And here’s another solution: a heat pump. Both ground-source and air-source heat pumps do a dual duty of cooling your home in the summer and heating it in the winter months. When you are cooling your home with a heat pump you are only using a fraction of the electricity needed for a central A/C system. Heat Pump systems are expensive up front, but can save you hundreds of dollars in heating and cooling costs, and will pay for itself in less than six years. In the summer, a ground-source heat pump takes the heat out of your home and transfers it into the earth through pipes running underground. The air-source heat pumps transfer the heat outside. (There are also heat pumps that can heat your water.) You can get a tax credit to purchase a heat pump system, and there are state and federal financial incentives that help pay for it.

There are many benefits to heat pumps. All the home cooling systems run on electricity, which means that they can run on renewable energy. But heat pumps are the most attractive heating and cooling solution because are wildly more efficient than either central air or window air units. Heat pumps also do double duty, warming your home in winter as well as cooling it in summer. We have over 1000 heat pump installations in Tompkins County, including several large developments, and more on the way.

Over 40% of all our energy use goes to cooling and heating our homes, so if we can reduce the amount of energy we use to stay cool, we can make a big difference in our energy footprint. Solving our cooling challenge means avoiding the normal energy-guzzling solutions, and joining the homeowners, landlords, and developers who are finding ways to reduce our community’s energy use. 

Last updated July 26, 2019