Solar battery storage thoughts can follow the successful execution of rooftop solar installation. You have done the economic analysis and the solar PV array will pay for itself in a few years. The self-consumption of the generated power pays for the system. Maybe with the feed-in tariff you have nothing to pay on electricity because it nets off against the power drawn from the grid when the sun goes down.

What happens after you get solar power with its PV panel array, inverter, and switches wired to your home?  Sometimes you think; “Why can’t that bank of photovoltaic electrical panels continue to power my home after the sun goes down?”

Your new solar power investment means neighbours becoming curious about your house. You are the new clean, green, renewable energy go-to-guy in the area about rooftop solar. The new rooftop panel fixtures create an interest in your home that had been absent previously.

This attention can become a little daunting. You’ve suddenly become the local solar expert where your neighbours consider you’re very likely across all solar installation costs. They are full of curious questions.

Why didn’t you buy or install batteries at the same time?

Did you look at the payback and decide to wait until the price dropped?

Have you got big plans for a home solar battery storage system later?

The questions make way for research.

How much will your solar investment cost you in annual maintenance?

Do you think grid energy pricing will vary in the next few years?

What is the best system to install and what did it cost?

With your cascade of questions coming from locals there is now even more to investigate.

Clearly your solar PV investment has been noticed and your environmental leadership will influence other energy conscious neighbours. You start looking at battery storage options. You’re likely to become self-convinced of returns being here and battery storage installation is considered. 

When you are already generating solar energy adding battery storage is an added marginal cost. Sure, you’re self-convinced that batteries will permit you to recover from the solar investment if used 24 hours a day. You’ll be secure in the knowledge that grid electricity prices invariably trend up over time. Should there be a power blackout you’ll have electricity to function normally.

What is the total costs of batteries? It will need to include safety isolation switching at the inverter and a regulator. There is the added cost of the electrical installation and some regular battery maintenance. Then you say to yourself; “This is an investment that will commence payback almost immediately”.

A brand new solar and battery storage package could cost as little as $5500 for 2kWh or much as $20,000 12kWh installed with control software. On top of the solar array installation that’s a major outlay. However, a battery storage investment will save you money on your annual electricity bills. Battery energy storage systems protect against random power outages, which can mean not having spoiled food or damaged electronic equipment.

The battery storage payback needs to be assessed independently of the original solar PV system. That means pricing the cash savings using electricity drawn from battery storage during the periods without sunlight and power outages. To achieve a payback period of say 10 years that extra annual saving needs to be around $2000 plus the opportunity cost.

Installing a home solar battery storage system means you’ll have power supply during a blackout. Your solar electrical generation installation can be isolated to operate independently of the utility grid. With a solar PV system (but no battery storage system) you might think you’ll still be okay. It’s true that the solar PV panels will provide DC power during daylight hours during a power blackout. Unfortunately you will not be able to use the solar power generated by your panels unless anti-islanding switching is provided onto the PV system at the inverter. In that case your inverter will have isolated your home from the grid to prevent electrical back-flow and then switches your home across to solar. That set-up is best run with batteries topping up the solar power if there is temporary drops in sunlight.

Practically, without this anti-islanding protection, connection isn’t permitted to happen for safety reasons. The roof solar power of your home’s PV electricity must be isolated at the inverter and not enter the grid. When you choose a grid-backed solar PV system your electricity production stops at the inverter during grid power outages.

The kilowatt-hours stored that a battery can supply depends on the battery type, deep cycle capacity and sometimes the brand (quality) of the battery. It’s important to install a solar battery system that stores sufficient power to run cooling in summer heatwave conditions. That level of solar battery storage will also ensure your home remains warm and operational during an overcast winter spell. I have explored solar battery technology in more depth in another blog on this website.

Your household might be run like an off-grid island for most of the year. On a practical level you may be unaware of power fluctuations or the lights going out in your neighbourhood.

Installing a solar system with battery storage can make good sense financially. For a first home purchaser doing that may be counter-intuitive. From a practical finance standpoint adding your solar PV plus battery storage installation costs onto your home loan makes sense. The financing costs for a home mortgage are generally better with having the advantage of longer term and lower interest rates.

You will need to assess the added cost of solar PV plus batteries to your home annual mortgage repayment. Then look at annual payback from this solar and battery investment. Adding say $25,000 to your home mortgage over 25 years might add $2200 per annum to your mortgage repayments. That figure will depend on the mortgage interest rate applied at the time and your loan eligibility limits. The solar system reseller may provide financial justifications that 'sell' the proposal to invest but at the end of the day, calculations in relation to savings and paybacks are yours to make.

Your annual savings for the solar PV and batteries may be $3000, which are added as extra paybacks to home mortgage payments. Your additional savings over cost of $800 from the solar and battery storage investment then reduces the mortgage principal every year. The solar and battery investment becomes effective if the savings are taken and put into the repayments.

The home mortgage is reduced more quickly because of the added home investment payback. As costs of grid electricity go up over time the resulting theoretical payback from savings could be increased. If those extra savings from the investment were actually realised and paid into the mortgage it would reduce even faster.

Postscript:

A friend who was reading about battery storage on this website saw reference to a new approach to battery storage for domestic solar panels on a youtube video of a presentation at the Australian National University (ANU) and he thought I could load it onto this blog page. Here is that short video below that he shared with us: