How much would I save on my power bill by getting new heating and air?

I realize this may be impossible to answer online (if anywhere) but I’m looking for a ballpark, because my current system does work now. I need to figure out whether it’s dumb for me to continue wasting money on more expensive power bills now, or whether it’s a small enough difference for me to wait until the thing actually breaks. I’ve got a guy coming over to give me an estimate next week and plan to ask if it’s significantly cheaper to replace a unit when it’s not freezing or sweltering outside and it’s not an emergency.

The house is about 1800 square feet, one story. Built 1928, mostly original windows (I’m replacing them gradually but it’s very, very expensive, especially since I live in a historical district and there are very strict rules.) Brick siding. Gas heat, electric air. The unit is about 20 years old, and the last repair was luckily covered under the home warranty I had at the time but would have cost almost a thousand bucks out of pocket. Since I’ve now replaced pretty much everything the warranty would have covered (except things like leaks where the coverage sucks), this year I put what I would have spent on the warranty away for eventual heating and air conditioning replacement.

I live in Columbia, SC, where the winters are relatively mild but where we probably use the heat more than less delicate people. Summers of course are hot. I have a programmable thermostat and we’re pretty miserly with the heat, but our gas bill alone last month ran to around $344. I mean, holy crap. In the hottest part of the summer, the electric does about the same thing. My dad built me a garage/workshop/garage apartment a few years ago with its own system, and the added expense to heat and cool that even with a tenant and the thermostat downstairs in the garage part is almost unnoticeable next to what the main house costs.

So. I understand that this house is just going to be more expensive to heat and cool, at least until I get the windows replaced, which will take years. I’ve done, er, three. I’m about to put some more insulation in the attic and build one of those foam board boxes around the attic access, which might help a little. Still, the house is generally decently insulated and except for the windows I don’t think we’re going to see a really significant gain that way.

With solely a new unit, more energy efficient, what magnitude of saving could I expect on the bill? (Of course there’s also a tax credit - got me four hundred bucks this past year on those windows.)

Have you looked into the efficiency ratings of your current vs. considered heating and air equipment? This is one way to estimate the expected drop in usage, and thus cost. Also, your local power company may have some program where they can audit your usage and tell you where your money would be most productively spent.

How do you find the efficiency rating for a current unit that’s 20 years old? Is it behind a panel or something?

ETA - As far as gas goes, my gas spending is effectively my heating spending. The only other gas appliances used regularly are the stove and the water heater, and both are new. The water heater is already turned down to a cheaper setting.

You could get a home energy audit. Go here to get a list of “raters” in your state. This site is actually for having your home RATED (for a tax credit), not AUDITED. However, if you click through to the company web sites you’ll find that many if not all of them do audits too…like this place in Greenville.

Having an audit can tell you how efficient or not efficient your heating and AC units are, as well as give you help on making other decisions on how to make your home more efficient - like caulking and insulating.

I plan on getting one sometime this year. Can’t wait!

I’m right up the road in Charlotte… One of the places I always recommend people check to get a basic idea, is

For your home - a 20 year old system - probably 9-10 seer. If you go by the calcs on the site and do NOTHING else, you will save about $400 per year, if you go to a 15 seer AC system.

From someone who has been around HVAC - you will save FAR MORE by replacing everything at once! ie: furnace and AC at the same time!

They have to pull half the stuff out, so you may as well do it all at once.

Typical AC only replacement - $3500-$6000
Typical Gas Furnace replacement - $1800-$3000

Doing them both at once will reduce the furnace rpl to almost the cost of the unit!

Mark - WebHVAC

Yeah, I was definitely going to get it all done at once - the whole shebang is the same age, so why not?

I went from Oil to Natural gas and new windows. Get a new gas furnace. They are very efficient and gas hot water and gas appliances.

My heat bill went from 300 a month to 50. My electric bill went from 125 to 70. I don’t have central air though.

It will pay for itself. The best part though is no more drafts and the tilt in windows are a breeze to clean. Sometimes the gas company will offer you rebates and incentives.

You can write this off on your taxes too.

I saved 35% on my electric bill by installing a new, more efficient, heating (gas) and air-conditioning (electric) system.

They offered “12 months no interest, no pay” so it was easy to pay it off over the year. The salesman used one of my electric bills as a reference point to show what my cost would be with the different seer ratings. He showed me which unit would be the best, in terms of cost and energy savings, for my house. (The more efficient units would not have saved enough in energy costs to justify the higher price)

My highest electric bill during the summer was $165.00 (thermostat at 76-78 most of the time) and lowest bill in winter at $55.00 (thermostat at 67 when at home and awake, 62 at night and when out of house) 2,000 square feet.

What annoys me is that I use 91 cents worth of natural gas and end up with a bill of $11.75 ($7.00 customer charge monthly plus three other charges and 3 taxes) My highest gas bill this year $110.00.

Well, I went back in my files and found that the customer charge was $10.10 back in 2006 (when I used 50 cents worth of gas and had a $14.99 bill), so I am a little less annoyed.

How sure are you? Have you actually opened up one of the exterior walls and looked? Even with a more efficient heating/cooling system if your home insulation isn’t adequate you will still waste energy.

This site has recommended r-values.

How is that?

More details and other potential tax savings here —>,,id=206871,00.html

Have I opened up a wall that’s brick on one side and plaster on the other? Well, no. People do that?

I’ve been meaning to ask if it’s possible to get extra wall insulation through the attic or crawlspace, though, and if so about how much it tends to cost.

When I bought this house just over 3 years ago, I had to get a lot of work done, including replacing the gas forced air and AC. The first month, December, the place was empty, with the thermostat set at 50 to keep things from freezing. My first gas bill from that period was for only 2 weeks and was $150 for just the gas. The furnace was replaced the next month, along with putting in a heat pump with a 13 SEER. The first month I lived here, in February when the temperatures were much colder and the thermostat was set from 64 to 70, depending on the time of day, my gas bill was around $45 for the month. With those kinds of savings, I consider the $5000 it all cost well worth the money.

My electric bill is higher now, because of the heat pump, but still not close to what just the gas was costing before. And I do have good windows, the people I bought it from replaced those, one of the few things they did that was a real improvement to the house. So I would recommend getting the furnace replaced and looking at a high efficiency heat pump instead of straight AC. Or even going one step farther and seeing about a geothermal system. I would have loved to put one of those in, but did not have the upfront cash for it at the time.

Which means, no insulation. The brick is a heat sink. What you will save with a more efficient heating/cooling system and insulation in the attic is going to be lost through the brick walls.

No, although some insulating services will drill a few small holes in the plaster and look inside with a small MI-5/FBI-type camera to see how much insulation you have.

Others can use a thermal imaging gun to check from the outside how much heat flux you have. Wish I had one, but they cost too damn much.

Often no, as there is typically a header and footer at the top and bottom of the wall (essentially, a couple of 2x4 or 2x6 or other wood beams together…YMMV).

If you have no insulation, then your best bet may be to have a company come out and drill a couple of small holes in the plaster between each set of joists and spray in expanding foam insulation.

I respectfully believe that the loss of benefit of upgrading the furnace but not attacking the wall insulation is somewhat overstated. The wall insulation is important, but depending upon your situation I’ll hazard that you will still save money and energy to a significant extent by upgrading your system. At least you should see if a company can give you a free examination/inspection and quote (if needed) for expanding foam insulation.

Is insulation in the walls something that could be done when windows are replaced, thus killing two birds with one stone?

Well…I’m sort of going out on a limb here, assuming standard US construction, but not very easily, except perhaps right around the windows themselves. The windows often either sit inside a structural frame and you don’t have access to the inside of the walls on either side. Even if you did, you’d only have access to the next joist, which at most is only going to be about 12-24 inches away. Again, I’m making a lot of assumptions here, given that home construction varies so much.

Wall insulation is often upgraded during a new sheetrocking or other new exterior or interior wall replacement. The expanding foam via holes is not as bad as it sounds - if done professionally it can give you an R value of between 3-7 per inch, so in a 2x4 space you would get from R10-20 improvement (with simplification…assumes proper installation, neglects conduction via steel joists, etc.) And if all you have is interior paint on your sheetrock, it’s not hard to re-paint after they patch the holes (which is part of the installation).

Isn’t sheetrock. 'S plaster. 'S a nightmare.

OK, expanding foam can still be used with it by drilling holes, and it can still be patched with plaster. This has been featured on This Old House or Ask This Old House. It’s either that or tear into the inside or outside walls. Again, I recommend getting a quote.

Consider getting a heat pump