UPS Calculation

[Frikkenator]

In general, is an inverter cheaper than a UPS? (For a similar wattage and up-time)
Edit: I'm also not sure that I understand the whole set-up... Is a UPS usually inclusive of a battery, or can you switch out batteries? Are batteries the biggest expense when looking at a UPS or inverter?

A UPS includes a battery, and inverter usually doesn't. I my case the battery in the UPS is not big enough for the uptime we require, so I picked a UPS that can be hooked up to extended run batteries, most home use UPS systems doesn't have this functionality.

I'm not sure on the price part, but in this case there isn't a big difference. The UPS I'm looking at is on-line which makes a big difference, and goes for just under R10k. Then each battery is an additional R6.5k, so the total is around R23k, whereas the inverter battery combo is R21k.

Keep in mind though that our power requirements are really low, if you go higher then UPS becomes drastically more expensive. Also this inverter has some advanced functionality and is quite small, you can get inverters for much cheaper than this, so I think overall the inverter + battery route will be much cheaper.

 

[The_Ogre]

In general, is an inverter cheaper than a UPS? (For a similar wattage and up-time)
Edit: I'm also not sure that I understand the whole set-up... Is a UPS usually inclusive of a battery, or can you switch out batteries? Are batteries the biggest expense when looking at a UPS or inverter?

A UPS is a device which contains one or more batteries, a charge controller and an inverter. Some do not come with batteries, but most do.

A pre-built UPS will work out cheaper than buying the charge controller, inverter and batteries individually, but a DIY solution will give you much longer backup time.

Yes, batteries are the most expensive part - however most consumer UPS's come with 1 or 2 standard 7ah batteries and these you can get from any alarm/security shop for ~R120

Only ever go DIY with these kind of things if you have some know-how on how they inter-operate, and how to connect them. The risk of electric shock is real!

 

[wvantzand]

Thanks everyone!

 

[russellw1]

An online UPS is equivalent to a sine inverter, batteries, and a good charger. My Masterguard 6kVA UPS cost R28k about 15 yrs ago but it has powerfactor correction on the charger and 20 good quality panasonic batteries. I don't use it now that the batteries are too weak to work because they would cost R6k or R7k to replace.