If you're going to spend big bucks on a TV, tech gadget or appliance, it pays to do research to find the best price. Deal and price-comparison sites can help you find the lowest price at the moment. But wouldn't it be nice to know whether the price is going to drop in the coming weeks or months? In other words, should you buy now or wait?

Free online shopping service Decide.com aims to answer that question for consumers. The site was launched about a year ago by the founders of Farecast, a travel site that predicted when airfares would rise or drop (it was bought in 2008 by Microsoft and now is Bing Travel). Decide.com analyzes historical price movements on electronics and appliances and the timing of new model releases for each product to predict whether prices will hold steady, rise or drop.

So if you're searching for a new TV, for example, Decide.com will tell you for each model whether you should buy or wait depending on its predicted price movement. The Decide.com team claims that its predictions are 77% accurate and, when they are right, the predictions save customers an average of $87.

Considering that 23% of the predictions aren't accurate, you shouldn't base your purchasing decision solely on Decide.com's buy or wait recommendation. However, the site has other features that can help you make the decision.

It provides a price-history chart for all products (when you click on the product) that shows the lowest, highest and average prices, which can give you a good idea about whether the current price on a product is a good deal. Decide.com also has reviews, news and rumors about products and a list of online stores selling the products and the total price, including tax and shipping. And you can set an alert for a product to receive an e-mail when the price changes.

Consumers now can get Decide.com's price predictions on the go with the Decide Shopping and Price Predictor App for iPads, which was launched May 3. So if you're in a store and didn't do your research beforehand, you can get information to help you decide whether you should buy a product.

Decide.com also has a new "Got Your Back" guarantee for customers who register (for free) as members on the site. It recommends 10 products daily, and if you buy one of the products and the price drops within two weeks of your purchase, Decide.com will automatically refund you the difference.

Reprinted with permission. All Contents ©2012 The Kiplinger Washington Editors. Kiplinger.com.