public Integer getPayBackTime() {
		
		for (int year = 1; year <= this.otherDetials.getPanelLifespan(); year++){
			if ((this.otherDetials.getCompoundInvestmentReturn(year) - 
					this.getCumulativeAnnualSavings(year)) < 0) {
				return year;
			}			
		}
		
		return 0;
	}