"Zeroing" the Monthly Bill
Cancelling/achieving a P0 Monthly Bill
There are 2 methods for completely eliminating your energy bill with solar. Let's compare the return-on-investment performance between the 2 system types. For this example let's say that this is a residence with an average monthly bill of P10,000. The energy consumption is fairly evenly spread across a 24 hour period with 1 AirCon unit running in the sala most of the day and two 1HP AirCon units run all night. We also assume that the grid energy rate is P11.5/kWh and that the roof has an optimal azimuth for the panels in order to achieve an average of 4.5 Peak Sun Hours (PSH). The average 24-hour energy consumption is therefore 29kWh.
Energy storage technology has made significant advances in the last few years with the mass commercialisation of large lithium-ion battery banks to power EVs (electric vehicles) and utility scale renewable energy storage. Prices have dropped sufficiently to make highly sophisticated hybrid solar systems financially viable compared with traditional grid-tie systems. The industry's present day mantra is "Storage is the future of renewable energy". We are proud to be at the forefront of this technical revolution in keeping with the global trend. Other installers in the Philippines are slow to adapt to this new and superior technology. A 6.3kWp hybrid system with 15kWh of lithium-ion battery storage would be sufficient to satisfy the total 24 hour energy consumption on most days. It will harvest 28.4kWh of energy per day. 15kWh will go to charging the batteries and the other 13kWh will be used to satisfy the daytime load. The nighttime aircon usage will draw 8-9kWh from the batteries leaving enough to spare for standard household appliances and a bit of reserve in case of a nighttime brown-out. The system is perfectly sized for 100% self-sufficiency so you do not need to buy any energy from the grid. The hybrid system is truly fit for purpose if you want to "zero" your electric bill. Click here to learn more about how a hybrid solar system works.
Grid-Tie - Yesteryear's method when energy storage was lead-acid battery based and too expensive
The grid-tie solar system must be twice as big as the Hybrid system because it needs to generate more than twice as much energy as you use in the nighttime since the cooperative will only credit your energy bill around P5/kWh that you export under net metering. During the 17 hours of no daylight the household consumes 20.5kWh. The solar system needs to generate enough energy to power the daytime load and export around 41kWh to the grid in order to earn enough credits to offset what you buy from the grid while the sun is not shining. That requires a 12kWp grid-tie solar system and you'll need a big enough roof to accommodate 40 panels as opposed to just 20 with the hybrid system; you may not have enough roof space to adopt this obsolete method. Grid-Tie solar systems reach a point of diminishing returns when the capacity exceeds "base load" for the very reason that the cooperative only credits you P5/kWh for exported energy. The best practice therefore is to size grid-tie systems to cover only the daytime base load for 100% self-consumption with very little excess energy to export; this yields the best ROI. The grid-tie system will also shutdown during brownouts rendering the huge 12kWp system completely useless; you are effectively still completely dependent on the grid and the coal burning plants that feed it. Hybrid systems are fit for purpose if your goal is 100% self-sufficiency. Click here to learn more about a grid-tie solar system works.
Let's look at the two systems side-by-side in the table below:
NOTE: 1. Assumes that the batteries will be expanded during the system lifetime to maintain storage capacity as the original batteries degrade slowly with age. 2. Assumes that the customer would opt for the top-of-the-line SolarEdge grid-tie system due to the number of panels and likely requires more than 2 orientations. A standard Solis system of this size would cost ~P800,000 up front. You can always start with a smaller solar system that fits your budget then expand it later to gradually get achieve your zero bill goal.
The two systems are virtually equal from a financial point of view. They have the same upfront cost and similar ROI; especially if you need to maintain a generator for backup power with the grid-tie system. The hybrid system is the superior choice from a technical and usability point of view. The hybrid system will continue to work automatically during brownouts which is very valuable when the Philippines is battered by typhoons and floods. As the name suggests, the grid-tie system is completely dependent on the grid and the government programs for net metering. The rules and regulations for net metering are reviewed and updated periodically and not always to the consumer's benefit. Any unfavourable changes would have a very negative effect on the ROI with the grid-tie system. The hybrid system puts you in control of your own power generation and isolates you from the grid, the energy cooperative, and future regulation changes with net metering.
A P1 million system is quite expensive but remember that you can always start with a smaller system that is within budget and apply the savings towards future expansion. Please contact us so we can answer any other questions you may have and quote the best possible system for you to achieve your renewable energy goals within your budget.
A quick note for our commercial and industrial customers
We do offer industrial grade, 50kW and 100kW 3-phase hybrid inverters with enormous high-voltage lithium-ion battery banks up to 1MWh of storage. It is technically possible to power your business entirely on solar energy with these systems. Even though the ROI is fundamentally the same as described above the upfront capital investment required is quite high and therefore a significant entry barrier. Most businesses have high daytime consumption so it is best to start with a modest 3-phase grid-tie solar system at first to cover daytime base load; that will yield the quickest ROI break-even. You may add a small hybrid system if you need UPS (uninterrupted power supply) for sensitive and critical equipment then grow it over time to increase your self-sufficiency.