Having an excess of credit available from your HELOC will not have a major effect on your credit score. If you go to MyFICO.com you will get information directly from Fair Isaac, Co., the creator and owner of FICO scoring, the most widely used credit scoring model in the United States. The manner in which you handle your unsecured credit, mostly credit cards and unsecured consumer loans is the primary factor that determines your credit score. The minor effect of secured debt, such as the HELOC you are contemplating, only impacts your score as it "rounds out" your credit profile into a normal mix of secured and unsecured debt.
One very important factor affecting your score is the ratio of your available credit to the credit that you have used. If you add up the credit limits on all credit card accounts then compare the aggregated balances (credit used) of the same accounts, the ratio will be a major determinant of your score. For example, if you have aggregate credit lines of $2,000 and have charged up $1,000 your credit available to credit used is 50%, a ratio that is not favorable for a good credit score. Ideally, this ratio should be around 30%. You might deduce that the credit line of your HELOC would naturally increase your unused credit and make your ratio very appealing. Not so, because the HELOC is a different type or classification of credit, secured credit, and FICO does not mix credit types to get the resultant ratio. So, the HELOC available credit does not materially increase your credit score.
You only mentioned the single kitchen project as the object of the HELOC proceeds, so I suggest you go with the $150,000 credit limit. To have a limit that is clear to you to be excessive is a bad idea, and you may have to pay points or even a commitment fee on the unused portion. Also, over time, you may be tempted to use the line-of-credit for financially questionable purchases and investments, which you would not have considered were it not for the ever-available credit line, that you didn't need to start with. Keep in mind that any purchases on this line-of-credit are secured by your home, which could cause a problem should an unforeseeable financial difficulties arise in the future.
You mention in your question that you plan to pay off the balance of your HELOC during the first nine months of the loan. Many HELOC agreements include a pre-payment penalty if the loan is paid off before the end of the "draw" period, or the period during which you can use the line of credit. For most HELOCs, the draw period is between five and ten years. If you plan to pay of the balance of the loan within the first nine months, make sure that you choose a loan that will not penalize you for your early payment.
To find more information about home equity lines of credit, I encourage you to visit the Bills.com Home Equity Resources page.
If you enter your contact information in the Bills.com Savings Center at the top of the page, we can have several pre-screened lenders contact you to discuss the options available to you.
I hope this information helps you Find. Learn & Save.