# Power Consumption: assess monthly and annual energy usage

4 steps to assess your monthly and annual power consumption. Find out the ideal size of your solar energy system.

## 4 Steps to asses your monthly and annual power consumption

What you need to start with                            Determining your load profile and your consumption trends is the first step towards properly sizing a solar power system.Performing this study will enable you to understand the size of a solar system you will need. Some PV installers might charge you for this, but it’s a fairly easy task to do by yourself, so no need to hire anyone for this!This step-by-step approach helps you calculate your annual/monthly power consumption in less than ten minutes.

### STEP-1: Collect data from utility bills

To collect all the necessary information, you will need to have a look at your past electricity utility bills.The more bills you will use, the more accurate your study will be.I advise to have electricity bills for a complete year, as 12 months will show your electricity consumption pattern over the entire year.

### STEP-2: Record consumption

Record the data from the bills on a piece of paper.Are you still with the same number of people in your household? To get accurate results the number of people using electricity should be similar as the past year.

### STEP-3: Calculate monthly usage

This total sum of all bills will provide you with the amount of electricity consumed by you over the period of one year.Divide it by 12 to obtain your monthly usage, divide it by 52 to obtain your weekly usage or divide it by 365 to obtain your average daily electricity usage.It can’t be more simple..

### STEP-4: Assess results

Once you obtain your average monthly electricity usage, you can use this figure to size your solar system.Assessing the results to size your solar system is the most important step. Make sure to add a 15% to 20% contingency margin to your results.If you are planning to expand your load profile (planning to buy more appliances in other words), add another 20% to cover for those future expansions.The final figure is the minimum size of the solar system that you would need to cover for all your present and future needs.
By

Peter Davies

on 01 Apr 2016

In the Philippines we have to take a more detailed and different approach to system size and design compared to other places in the world as there are paradigm differences as follows: 1. Anywhere outside MM has to allow for regular or intermittent brownouts (blackouts) due to a) insufficient generation capacity and b) fragile and insufficient grid capability and c) still 2.5M households completely off-grid. 2. As the Philippines is disaster-prone, some brownouts in some areas can last days, weeks or even months (Typhoon Hainan in 2013) 3. Systems therefore have to be with hybrid inverter and batteries making unit costs/watt expensive, especially as systems are small (average rural electricity is <100Kwh/mo., urban average - 250kwh/mo.) 4. Electricity rates are very high (\$0.21/Kwh) - double that of China and developing nations in S. E. Asia. 4. Limited financial capacity of households and limited funding/grants. 5. Seasonal variation of demand is high. The hot season is double the load (triple or more if the household has air conditioners) - fortunately this is also when supply is greater. 6. Net metering is a) expensive and slow (3+ months) to arrange and b) not effective as it only credits at the generation rate which is 50% of the total charge. As systems have to have batteries anyway (SLAs until Li-ion is cheaper) better to not net meter and use the battery power, switching to utility if used up. 7. A system designed for 100% power in the hot season would be very inefficient in the cooler season as it could not store all available power. Therefore a middle range solution is desirable, especially as it can then take advantage of the lower tiering rate at low demand levels. This adds 15-20% to the savings making ROI better. A 1KW system (costing \$ 1,800-\$2,000 installed)for a house that averages 200-500Kwh/mo. throughout the year has a 5 year payback.

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