Hello my name is Mike and thanks for using Just Answer. There are a few variables involved in giving this answer.
Here is a link to where you can apply your variables (wants/needs) to an equation to get the result. You will be able to determine a range of heater sizes. Please only click accept if this answer meets your needs. If not, please reply saying so and I will opt out of this question and allow another expert to assist you.
I hope this information was helpful to you in answering your question. If so, please remember to click the ACCEPT this answer button. Thanks.
Mike W.
General C&ontractor
20 years exposure to the Home Improvement industry.