What Do I Need to Know When Buying an HVAC System?

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• on October 27, 2011
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An HVAC system may be the most expensive system in your home and it is certainly one of the most crucial.  You may be wondering, “What do I need to know when buying a HVAC system?”  This guide answers that question with tips that will help you select an HVAC system that will make your home very comfortable while providing you with the right balance between equipment costs and energy efficiency.

Here are the things you need to know when buying an HVAC system.

The Form of Heat you will Use in your HVAC System

Gas furnaces remain the most common heat source in today’s homes.  Oil furnaces are used in homes that are already set up for one, including an oil tank, oil line and the necessary venting.  Oil furnaces are rarely installed in new construction except in the northeast where natural gas isn’t plentiful. Gas furnaces mostly use natural gas but where gas line isn’t run, they are easily converted to use propane gas.  Gas furnaces are affordable and efficient.  They work well in any climate, including the coldest ones.

Heat pumps are another popular option.  They are essentially air conditioners that supply heat by reversing the process in winter.  Heat pumps can be more efficient than gas furnaces in mild and warm climates.  Another advantage is that they don’t burn fossil fuels and don’t need to be vented or have a fuel line run into the home.  In cold climates, heat pumps are not effective and your best choice is a gas furnace.  In mild and warm climates, heat pumps are a very strong option.  Learn more about heat pumps on this site to help you decide whether a furnace or heat pump makes more sense for you.  They both work very well and the chances are, you’ll be happy with either one.  In a cold climate, consider a dual fuel heat pump. These models work in the same system as a furnace.  The heat pump provides efficient, comfortable heat in cool weather and the gas furnace supplies heat when the weather turns very cold.  It’s the best of both worlds, and while equipment costs will be slightly higher, your energy bills will be lower by taking advantage of the most cost-effective fuel source.

The Level of Efficiency in your HVAC System

The rule is that the more extreme temperatures are in your area, the higher the efficiency your HVAC system should have.  Furnaces range in efficiency from 80% to 98%.  The more efficient the furnace is, the more it will cost.  However, it will cost less to operate.  The amount of time it takes to recoup the extra expense of the furnace through lower energy bills is called the “payback period.”  In a warm climate, the payback period on a high-efficiency furnace might be 7-10 years and you are better off with an 80% efficient furnace.  In moderate climates with chilly weather, a 90% to 93% efficient furnace might have a payback period of 3-5 years while a high-efficiency furnace might have a payback period of 5-7 years.  In cold climates, your payback period on a high-efficiency furnace might be 2-5 years, making it a cost-effective choice.  Stay away from an 80% efficient furnace in cool climates because your fuel bill will be very high.  In any climate, your choice will also be affected by how long you plan to live in that home.    The longer you plan to stay, the more efficient your furnace should be in order to achieve the best long-term value.

In terms of air conditioners and heat pumps, efficiency ranges from 13 SEER (seasonal energy efficiency rating) to currently about 22 SEER, with more efficient models being introduced every year. As with furnaces, the more efficient the heat pump, the more it will cost so choosing the right model for your climate is important.  In warm climates, choose a model 16 SEER or higher.  In mild climates, a less efficient model will be more cost-effective.  Of course, in any climate, if your goal is to use green technology, choose the most efficient products your budget will allow.

The Level of Quality you Want in your HVAC System

You get what you pay for in HVAC equipment, just as in most other things.  Most manufacturers make several grades of equipment to meet a range of budgets. For example, Lennox offers the Dave Lennox Signature Series as their top of the line; the Elite Series is next, and the Merit Series offers the least quality but the most affordable price.  For Carrier, the series, from top to bottom, are Carrier Infinity, Performance, Comfort and Base.  What is your budget?  How long do you plan to be in the home?  These are the primary factors in the level of quality you choose.

Performance Features in your HVAC System

Manufacturers make standard-performance equipment and high-performance equipment.  The better the performance, the more precise control you have over indoor climate and comfort.  High-performance HVAC equipment is also more expensive.  You have to decide whether precise home comfort or lower equipment costs are more important to you.

Furnaces: Standard furnaces have a single-stage gas valve and a single-speed blower.  They are either on or they are off.  Better models may have a multi-speed blower motor that starts out slower while air is still being heated, eliminating a blast of cold air at the beginning of the cycle.  High performance furnaces will have a 2-stage or modulating gas valve and a variable-speed blower.  The burner fires on lower capacity most of the time and the blower matches the burner by running more slowly.  The result is longer cycles that produce very balanced temperatures with little noticeable fluctuation.  They are quieter, too, and filter the air more consistently.  When the furnace is working with a central air conditioner, it will eliminate more humidity during cooling.  Air handlers used with heat pumps may also come in single-speed and variable-speed models.

Heat Pumps and Central Air Conditioners: Standard models have single-stage compressors with on/off functionality.  Better heat pumps and ACs have staged operation delivered by a 2-stage compressor, a modulating compressor or 2 separate compressors.  Staged heating and cooling is more comfortable and quieter.  If you choose a model with staged operation, it will be important to match it to a furnace or air handler with a variable-speed fan to take advantage of the staged heating or cooling.

The Size of the HVAC System

Ask your HVAC contractor about doing a load calculation for your home. This takes into account size and construction factors of your home as well as the local climate and other issues.  The load calculation will determine the right capacity system you need.  Having an HVAC system that is too small means it won’t heat or cool effectively.  One that is too large will waste energy.  In new homes, a load calculation should definitely be done.  In existing homes, if the house has changed since the last system was installed, a new load calculation is a good idea.  Adding attic installation, replacing old windows with energy-efficient ones or replacing the roof can all alter the size system you need.

Summary

These factors are what you need to know when buying an HVAC system.  They will help you decide the type of system best suited to your home, your budget and your needs.