Conver Java Applet to javascript

I have designed a simple energy calculator as a Java applet that I display on my website. The applet load time and browser/Vista compatibility problems have become an issue. I would like to convert this application to javascript (or a similar suitable script) to avoid these problems. The calculator simply calculates the savings to be made if a user converts from traditional bulbs to energy efficient equivalents. The user is presented with 2 rows. Both rows are pre loaded with 20W and 50W traditional bulbs on the very left hand side. These are non editable. The only editable fields for the user are the quantity and bulb usage. The user currently enters these details via comboboxes but this can be changed if required. I selected the comboboxes for the java application just to avoid people entering illegal characters. All the logic/calculations required is already implemented in the Java applet. All that is required is to convert this to a javascript application. I have attached a screenshot of the applet and the (inefficient)java source code. All the java code is currently lumped into one class in an attempt to speed up applet load time.