Replacing your home's heating or cooling equipment costs thousands of dollars. Even on cool days, such expenses could make you hot under the collar. So it makes sense to maintain your current equipment properly and get good repairs when needed.

When you do need new stuff, you will want to work with a company that offers the best possible advice and prices. Checkbook's evaluations of Twin Cities area heating and air-conditioning services for quality and price will help you find a competent contractor. Through special arrangement with the StarTribune, you can access Checkbook's ratings of local HVAC services for quality and price free of charge until Nov. 1 by using this link:

For quality, Checkbook's surveys of local consumers turned up dozens of excellent outfits. Several companies were rated "superior" for "overall quality" by 90 percent or more of their surveyed customers. But not all contractors are up to the task: several others scored much lower, receiving such favorable ratings from only 60 percent or fewer of their surveyed customers.

Checkbook also found very big price differences. For example, to replace the blower motor and capacitor for a Trane furnace, local companies quoted its undercover shoppers prices ranging from $308 to $1,046. And to supply and install a Honeywell programmable thermostat, prices ranged from $195 to $900.

If you need a new furnace or air conditioner, get several companies to prepare written proposals to install it. Although obtaining multiple bids for new equipment will save most consumers thousands of dollars, most don't bother to do so. Carefully compare proposals. Designs can affect how quickly and uniformly your system heats and cools your house, how much energy it consumes, how much noise it makes, what drafts it produces, the amount of space it occupies, maintenance requirements, and other important aspects of performance.

When buying new equipment, be skeptical about claims of cost savings from a more energy-efficient system. There may be substantial savings — and there are compelling public-interest reasons to install efficient equipment — but some companies exaggerate the amount of savings. Get several companies to make proposals, ask for documentation of how much the new equipment will cut your energy bills, and ask questions. You can calculate your own estimates by using the U.S. Department of Energy's Home Energy Saver tool at its website.

For an illustrative home, Checkbook estimated how energy costs are affected by purchase of new equipment with varying energy efficiency ratings and found:

• For furnaces, it usually makes sense to pay extra for a more efficient furnace, compared to buying a minimally efficient model.

• For air conditioners, in this area it usually doesn't make sense to pay more for highly energy-efficient models.

• Ground-source heat pumps (also called geothermal systems) provide very low heating and cooling bills, but these systems are extremely expensive to purchase and install — typically $30,000 or more. It makes financial sense to consider them if you know you will be in your house for a long time.

Some additional points:

• When comparing models, look for energy-saving features such as variable-speed blowers and two-stage burners. Presence of these gadgets will help save energy, but won't be reflected on their models' efficiency ratings because ratings are determined while equipment operates at full capacity. A variable-speed blower, for example, usually runs at a constant low speed to maintain the correct temperature, increasing speed and energy use only as needed.

• Investing thousands in ultraefficient equipment makes no sense if your home is poorly insulated, or your thermostat is pegged on Tahiti during the winter. Before upgrading your equipment, make sure your attic is well-insulated and seal up easy-to-fix leaks (at, you will find advice on these topics).

Before hiring a company for installation work, ask for performance guarantees that specify how warm the equipment will keep your house — and for air-conditioning equipment how cool — and how uniform the temperature within the house will be when outside temperatures reach a specified level.

Heating and air-conditioning services are likely to push for annual maintenance visits, and many will offer a contract. Such frequent service may not be needed as long as you are diligent about the most important maintenance task: replacing air filters whenever they get dirty.

Whether you need repairs or a new unit, pay with a credit card. If you are dissatisfied, you can dispute the charge with your credit card company.

Twin Cities Consumers' Checkbook magazine and is a nonprofit organization with a mission to help consumers get the best service and lowest prices. It is supported by consumers and takes no money from the service providers it evaluates. You can access all of Checkbook's ratings of area heating and air-conditioning contractors free of charge until Nov. 1.