If it worth installing solar if my roof faces east and west not north?

It really depends on the clients standard energy usage patterns. In general we this will be losses in the total yield that can be produced during the day but depending on your usage if your not at home in the middle of the day and you can not use the power then there is a good chance that this power may be feed back into the grid and subsidised at a much cheaper amount then that of which you have to pay your retailer. If you can use the power from the east in the morning and you get home and use most of your production during the afternoon between 4 and 8 pm then you could use this power from your roof and minimise the amount that you have to rely on the grid saving you money.