Energy-Efficient Space Heating and Cooling
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Properly heating and cooling your home is one of the most important things you can do to improve energy efficnency. This is because over 44% of the average utility bill is for heating and cooling costs.
Cooling
Tips for reducing air conditioning costs.
- Keep the temperature at 78'F or higher. For each degree below 78'F, you will increase your energy consumption by approximately 8%.
- Minimize use of bath and kitchen fans.
- Clean the indoor and outdoor coils on the ac unit. If the indoor coil has substantial dirt build-up, it will greatly reduce efficiency.
- Reduce your dependency on air conditioning by keeping heat out of the house. For example, shade windows which let sunlight in. In addition, delay activities such as dish washing until evening. These activities generate a substantial amount of heat.
- Keep the house closed tight during the day.
- Unless it is really hot outside, cool down the house at night using windows and fans.
- Avoid using a dehumidifier at the same time your air conditioner is operating.
- Use ceiling fans. This will allow you to increase the temperature in your house by approximately four degrees and yet feel no change in comfort.
Questions to ask when purchasing a new air conditioner. Does the air conditioner...
- operate quietly?
- have a fan-only switch? This is useful so you can use the unit for nighttime ventilation which will substantially reduce air-conditioning costs.
- have a filter check light to remind you to check the filter after a predetermined number of operating hours.?
- have an automatic-delay fan switch to turn off the fan a few minutes after the compressor turns off?
Heating
One of the best and easiest ways to lower your heating cost is to simply lower the temperature in your home. If you put on a little more clothes, you can save a substantial amount of money by simply keeping your house 5-10 degrees cooler.
If you wish to do more than simply lower the heat in your hose, consider making some calculations. Below is a formula that will help you calculate energy cost. To use the formula, use a decimal for the appliance heating efficiency (which is obtained from the first table below). In addition, you need to convert the Btu content of the fuel per unit to millions of Btu by dividing the fuel's Btu content per unit by 1,000,000. For example: 3,413 Btu/kWh (electricity) divided by 1,000,000 = 0.003413. The formula:
Energy cost ($ per million Btu) = Cost per unit of fuel ÷ [ Fuel energy content (in millions Btu per unit) × Heating system efficiency (in decimal).]For example:
Propane (in medium efficiency central heating system) heat cost = $1.09 (price per gallon) ÷ [ 0.0913 × 0.85 (efficiency) ] = $14.05 per million Btu.
Below is a table of estimated average fuel conversion efficiency of common heating appliances.
| Fuel Type | Efficiency (%) |
| Coal (bituminous) | |
| Central heating, hand-fired | 45.0 |
| Central heating, stoker-fired | 60.0 |
| Water heating, pot stove (50 gal.) | 14.5 |
| Oil | |
| High efficiency central heating | 89.0 |
| Typical central heating | 80.0 |
| Water heater (50 gal.) | 59.5 |
| Gas | |
| High efficiency central furnace | 97.0 |
| Typical central boiler | 85.0 |
| Minimum efficiency central furnace | 78.0 |
| Room heater, unvented | 99.0 |
| Room heater, vented | 65.0 |
| Water heater (50 gal.) | 62.0 |
| Electricity | |
| Baseboard, resistance | 99.0 |
| Central heating, forced air | 97.0 |
| Central heating, heat pump | 200+ |
| Ground source heat pump | 300+ |
| Water heaters (50 gal.) | 97.0 |
| Wood & Pellets | |
| Franklin stoves | 30.0 - 40.0 |
| Stoves with circulating fans | 40.0 - 70.0 |
| Catalytic stoves | 65.0 - 75.0 |
| Pellet stoves | 85.0 - 90.0 |
To consider energy efficnency, you need to consider the heat content of different types of fuel. Below is a table of average Btu values for different types of heating fuels.
| Fuel Type | No. of Btu*/Unit |
| Fuel Oil (No. 2) | 140,000/gallon |
| Electricity | 3,412/kWh |
| Natural Gas | 1,025,000/thousand cubic feet |
| Propane | 91,330/gallon |
| Wood (air dried) | 20,000,000/cord or 8,000/pound |
| Pellets (for pellet stoves; premium) | 16,500,000/ton |
| Kerosene | 135,000/gallon |
| Coal | 28,000,000/ton |
*The British thermal unit (Btu) is the most commonly used value for expressing the energy value or heat content of a fuel in the United States. One million Btu is the heat equivalent of approximately 7 gallons of No. 2 heating oil or kerosene, 293 kWh of electricity, 976 cubic feet of natural gas, 11 gallons of propane, 125 pounds of air-dried wood, 121 pounds of pellets, or 71 pounds of coal.
Alternative types of heating:
- Solar energy
- Geothermal heat pump
