Ok, so running the numbers of the current washer and dryer, and basing them off the Amp usage listed on the machines using Amps x Volts = Watts

.....

Issues with assumptions:

The listed amp rating is the maximum possible power draw of the unit, not the amount used whenever the unit is on. That rating is usually used to tell if your circuits can properly handle all the devices you're plugging in so that you don't blow a fuse/trip a breaker if you decide to have everything on at once. The actual power usage for both units is substantially lower. Sadly it seems that dryers don't come with energy guide ratings and that efficiency isn't enormously different between units.

You're using a figure of 2.23 cents/kWH for electricity. That's only the charge for your distribution costs. I also have Dominion Power in Virginia-we both get charged for distribution, generation, transmission and fuel costs plus state tax plus city tax per kwh. Total electric cost is around 13.2 cents/KWh in my city. Check your bill and divide your amount due minus flat customer fees by total Kwh used to see what I'm saying. When using my electric cost figures, estimates of energy usage using your amp rating look very flimsy. I'm getting around $34/month just to run the dryer with the energy consumption you estimated. This calculator is estimating just $11.90 a month to run 30 full loads at high heat at 13.2 cents/KWh. I don't think you can rely on amp ratings to get any reasonable sense of the devices usage.

http://www.csgnetwork.com/elecenergycalcs.html.

Dryer savings:

Energy costs for your dryer is just going to have to be nearly pure guesstimation, but assuming the difference in amps directly corresponds with total energy usage, the new dryer will use 24A/28A= 85.7% of the energy per hour as your old unit. You'll have to run the two just as much with the same washer, so it's best to do an apples to apples comparison. Using the cost from the calculator above:

Old dryer- 11.90/month*12=$142.89 to run 360 high heat full loads a year

New dryer=$142.89*85.7% the energy=$122.38 a year

Difference= $20.51

TOTAL DRYER SAVINGS: $20.51

So that's about $20/year savings as a rough guess. And pretty believable. While there have been enormous improvements in lots of other appliances like refrigerators, TVs, computers, lights, etc, there's a basic issue of physics with dryers that you need an enormous power to create enough heat to dry clothes and dryers have not seen the same enormous improvement.

Washer savings:

Washer water savings: Your figures look reasonable. I'll just take the averages of your high and low estimates:

Old: $89.81

New:$40.65

Savings: $49.16

Washer Energy Savings:

As above, amp ratings are rather unreliable. Take a look at the energy guide rating for the new washer:

http://products.geappliances.com/MarketingObjectRetrieval/Dispatcher?RequestType=PDF&Name=GHWN5250D.pdf -- Adjusting for your usage (6 loads vs. 8) the washer uses 162.75 kWH, multiplied by my electric rate as a proxy for yours (13.2 cents/kWH) I get an annual cost of $21.48. I think the label assumes warm water usage or whatever the default cycle is.

You might be able to find one for your old washer as well if you get the make and model and google around. Without that, I'll just assume the new model is 20% more efficient, as that's what the energy star site says it is, generally:

http://www.energystar.gov/index.cfm?fuseaction=find_a_product.showProductGroup&pgw_code=CW#overview21.48*1.25=26.85 annual cost for old dryer

Energy savings of $5.37

Fringe Dryer Savings from the Washer:

If you buy the Washer, you'll have to run your dryer less, you think just 2/3rds as long. If you keep your old dryer, that's a savings of $47.63 a year or if you get the new dryer, $40.79.

Savings from directly from new washer per year: $54.53

Additional savings from new washer if you only need 2/3rds of the time to dry a load: 40.79-47.63

So a new washer alone for $500 is definitely looking like a reasonable buy, especially if you really do need less time to dry your clothes. Breakeven time will be 5-10 years, maybe sooner if electricity goes up. The dryer doesn't seem like such a great choice, around 25 years. But my dryer energy consumption estimate makes some big assumptions, so who knows. Hope this helps!