Whole house Backup Battery system with existing solar

I have 36 Sanyo HIP-195BA 195 W solar panels with 7KW SMA Sunny Boy inverter. I’m looking for recommendations for a Lithium battery whole house backup system for when PGE goes down for several days.

Hi @eng1el

I imagine you would first need to significantly increase your solar size if that is your aim. However, first of all, how much electricity (in kWh) do you use daily on average, in summer and winter?


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In the winter, it’s about an average of 800kWh. Summer is 325kWh on average. I’m looking at the Simpliphi battery system, 6 batteries (22.8kWh), with Slo Ark 12K inverter. My panels were installed in 2009 and have a 20 year limited warranty. I’d like to avoid changing the panels.

Hi Marty,
Thanks for taking an interest in my situation. I appreciate it. I logged onto my PGE solar account and have attached a snapshot of my energy use from 2/20-2/21.
I’d like to keep my existing solar panels, they have a 20 year limited warranty that ends 2029. My primary goal is to have power when PGE blackouts occur and secondarily, to use battery power during peak hours to lessen my PGE bills.

Hi Jim

I definitely wouldn’t suggest removing your current solar system. Have you got room to add any more?

Your solar system will produce about 10-20kWh on average per day in winter depending on where you are. I’m assuming the 800kWh is per month, which is about 26kWh a day. That’s on top of the solar that you’re using as well.

We’ve got a tool that simulates this, we’re working on a US version, but I’ve tried to simulate it here, this is showing a typical day in winter.

The first graph is simulating a 6.5kWh battery bank. Your solar system will fully charge this battery bank, but it will only give you a few hours of autonomy.

This second graph is simulating a 20kWh battery bank. You can see that your solar system won’t charge this battery bank higher than 50%. You can charge it from the grid though.

G’day Marty,

I believe the First image is a perfect example of a Energy Storage & Solar Generation wrongly set-up !

We consider Investing in more kWh of Energy Storage, would have eliminated Paying for little more than the $80 to Remain Connected into the State Grid,

OH, and that $80 charge means you the Generator, have to first Gift 800kWh of Energy to Just break even with that Charge. Not to mention, All your other Excess solar Energy sent into the Grid is making 300% odd profit for the Retailers ! :rage: (We are Against Generators having to Pay a Connection Fee as it would be Farer !)

Currently Two 10kW LiPO4 Battery cost around $8’000~$9’000, with 80% DOD, provides a minimum16kWh of Usable FREE Power. (other than the system cost)

So, we consider lining our Own pockets is far more intelligent, to invest in More Energy Storage than Solar, as Solar is way Cheaper to Purchase & add later-on.

The KEY is purchasing approx. Double your average daily Energy consumption, as will give you Instant Energy Independence, other than possibly needing to start a super Quiet 170cc Fuel Generator for a few hours, in Extended bad weather !

Where was I, yes, A DAT-4 unit would Generate 19kWh per Day with just Four 440W Solar Panels, that cost approx. $6’000 if you do the Trenching & Foundation work yourself.

If On -Grid you will need to engage a CEC accredited Electrician to inspect & Pass your System

If Off-Grid a Registered Electrician is suffice.

RESULT: $15’000 to become Energy independent for the next 30 years, excluding an Equipment failures or Damage.

This System would Greatly change the Efficiency of your System Figures shown above.

The sol-ark inverter seems to be a popular choice in the US and has generally very good reviews. It’s also able to operate in on-grid (hybrid) and off-grid modes and would provide a high level of backup power (9kW at 240V and 4.5kW at 120V - see specs attached). It should also be able to work directly with your existing solar array depending on the string configuration?

Simpliphi batteries are also very good, high quality, modular battery option. Although you would need closer to 30kWh of storage capacity to last several days - remember the batteries should not be fully discharged.

the cost of 30kWh batteries is beyond my budget so I’m hoping to ration my power usage to essential circuits: freezer, refrigerator, water well pump and hopefully get by with fewer batteries. Is this fantasy on my part?

@eng1el, not a fantasy. I believe you should be able to get by on a 20kWh battery if you ration your power usage. I have a small 16kWh battery and can run a single fridge, lights, small pump, computer, TV etc for 3 to 4 days no worries.

Currently 30kWh LiFePO4 cost just under $12’000, the price one pays for Energy independence!