# Feedback for inverter I'm building for Solar Panels

#### EB255GTX

Joined Apr 30, 2011
62
Yes, the grid-as-storage concept is what I was refrring to...no batteries required Solar systems that are just going to charge batteries can be a lot simpler, as you only need to condition the DC from the panels to make it suitable for battery charging (assuming a seperate inverter, or DC powered equipment only)

The next step is grid-isolated AC, whcih again can be quite simple as you are not trying to make an exact replica of the AC mains, just close enough and there is a lot of margin in that.

Much harder than either of these is grid connected inverters, but it has the advantage of not requiring battery storage, and having no practical limit to the amount you can generate (unlike batteries where any excess you are able to produce once the batteries are full is wasted)

#### wayneh

Joined Sep 9, 2010
17,153
... in order to make a project of building solar panels ROI worthwhile building the inverter myself would be necessary.
....The goal is to hook this up to the grid (of course) and roll back the meter on occasion. There will be approximately 600w peak attached to this.
So you want a grid-tie-in system giving a decent ROI on a 600W max solar installation.

Being generous, my math says you might get 10 hrs of peak output per day, or 6 kWhr. At my house, I pay on average just 3¢/kWhr. That'd be 18¢ per day assuming 100% efficiency. I'd be surprised if real results averaged more than half that, considering clouds, winter, electrical inefficiency, and so on. So maybe 10¢ a day or $37/yr is a decent back-of-the-napkin estimate. A perpetual stream of payments - an annuity - of$37/yr is worth the annual payment divided by your discount rate, the time value of money. Let's say that's 4%, giving a lifetime value of $925. Less if it doesn't last forever. If you can build me a permanent grid-tie-in installation, 600W peak, for less than$925 with lifetime warranty, send me a PM.

#### tommydyhr

Joined Feb 3, 2009
39
I pay on average just 3¢/kWhr.
Really? In Denmark we pay roughly 60-70¢/kWhr. :/

#### wayneh

Joined Sep 9, 2010
17,153
Maybe we could make a business charging batteries here and selling them there!

And yes, it really is that low here. That's an average cost for the year. At this moment I'm paying only 0.8¢/kwhr, which is oddly low although I've seen it go to zero. Really wish I had a big battery for that. But of course in the hot summer days it shoots up to 20¢ or more. I have a service where I pay the actual hourly rate, allowing me to shift my consumption to low-cost times of day. This generally means I run the dishwasher late at night and avoid the late afternoon rate peak.