function pv_size()
{

var insolation = 0;

//set seasonal insolation from checkboxes
if (document.forms[0].winter.checked) insolation = 4

else
	{if (document.forms[0].autumn.checked) insolation = 5

	else
		{if (document.forms[0].spring.checked) insolation = 5

		else
			{if (document.forms[0].summer.checked) insolation = 7

			else
				{alert("Mevsim Seçmelisiniz")
				return false
				}
			}
		}
	}


// validate input and set load to value of input
if (document.forms[0].load.value == "")
{alert("Enerji Tüketimini Girmelisiniz")
return false};

var load = document.forms[0].load.value;

// calculate result for peak mismatch of 1.2
var result = load/insolation*1.2;
result = Math.round(result);

//validate result

var verify = isNaN(result);
if (verify) {
	alert ("Enerji Tüketimi Rakam Olmalıdır");
	document.forms[0].load.focus();
	return false;
	};

// write result to form
document.forms[0].result.value = result;
}