Place to start - am I thinking about this backwards?

[agtcovert]

Hello all,

As I've done an upgrade project on my RV, it's inspired me to start looking at what options there are for our house. I had never paid much attention to our power bill, and I started looking at the peak rates. Not nearly has high as other places in the US, but quite high. I run some servers (part of my work, to a degree), and during the summer we like to keep the house cool so our AC is on quite a lot -- it's a new unit. We also invested in a heat pump water heater. I recently set up an Emporia to start gathering data on our usage, which has been fascinating to see.

I'm looking to start building a system incrementally. We have some space for panels, but I need to think on that more in terms of where would be a good place and also find out if there are any permitting requirements here.

So, I'm curious if anyone has started out with an inverter and expandable but smaller battery bank. Between 11pm and 5am, the power rate is extremely cheap. I'd like to be able to run my bigger loads on battery during those peak hours and then just recharge off the grid when it's cheap. I'm not talking whole home (yet). I have a small bypass and a large portable generator we run if the power is out. We're on well water, and our sump pump needs to run all the time given the water table. (I looked at a battery backup for it, and it was cheaper to get a bypass/generator/etc). I'm thinking of this as kind of an augmented critical loads setup to start.

In the future, I want to add solar. I don't know if I'll ever care about net metering/grid tie sellback; I do want to be tied to the grid. We get power from a smaller, local co-op. They require inspection, 24/7 access to shut things off, and periodic inspections. Just doesn't seem worth it.

I'd love any advice and input on my line of thinking. Many thanks!

 

[DIYrich]

If you don't want to export to the grid, the eg4 6000xp is a good place to start with just batteries.

Note the charge/discharge losses when taking advantage of time of use rates. 10-15% loss is typical.

If you need more than 6000 watts, then either parallel a second, or skip to the 18k pv, or sol-ark 12k or 15k. These can also export to the grid.

Note: I don't think the 6000xp can "supplement" from grid (xp provides 6000 watts, and rest comes from grid). The 18k pv and sol-ark can.

 

[agtcovert]

Thanks for the response.

Can you help me understand a bit more about the charge/discharge losses you mentioned?

There are so many options / configurations I could see, it's honestly a bit confusing. I tend to be a 'do it once, do it right' kind of person, and I can tell from everyone here that dipping your toe into this is just the beginning. I mean, I'm fully immersed trying to learn just from an RV project -- my point being I'd rather start with an inverter that will meet my current and future needs. I think it's safe to say the future needs will be there soon enough. It's a question of $$ and where I could put panels. I don't want them on my roof.

Back to equipment, inverters specifically: is the general recommendation from everyone to go with one of the AIO options? I'm admittedly drawn to Victron. I'd been looking at two of their Multiplus II 5000VA inverters paralleled. Based on the data I'm getting right now, we peak around 8-9kw of draw at max. I'm still chasing some circuits that aren't labeled (UGH) but they don't appear to have significant draw.

My plan is to put in a new subpanel and move over circuits I want inverted. I get battery backup, could still tie in my generator if needed, and with the right setup, I'm isolated from power going back to the grid and can do the work myself. After looking at my main panel and paying what I did to have it redone, unless I need to move the mains, DIY for me.

 

[DIYrich]

Thanks for the response.

Can you help me understand a bit more about the charge/discharge losses you mentioned?

Let's say your inverter is 95% efficient. It takes about 1.10 kWh of grid power to put 1.05 kWh of power into the battery. When you take the power out of the battery, you get 1.00 kWh of power from the 1.05 kWh in the battery. Round trip, it takes 1.10 kWh of power when cheap to provide 1.00 kWh of power when expensive. If you have a price difference of 2-3x, the 10% loss is negligible.