Nothing that wont be costly later. Best to do it now before it gets too big.
Most Ciscos are 12dc inside, we power them with a 200w buck converter from 24v systems. So the idea they are power hungry is partly a misnomer. Some devices are power hungry when they are fully loaded, c6500 or c4507 with dual sups and full of 48 port poe line cards will suck back the watts. A isr2951 pulls 65w passing 200mbps and its older brother isr3825 pulls near 80w passing 100mbps. The ASR series is even more power thrifty. Since most of your traffic will be hardware routed, CPU usage will be low, we are seeing 30% up to 50% for short periods and its the CPU that hogs power until you add HWICs or network modules like switch or service modules. Cisco does tend to put larger than necessary power supplies as they have no clue what we do with the hardware, configuration wise, but that does not mean its fully used all the time if at all.
A typical solar site for us has a c2960s and at least a c3825 but lately c2951s are more common since they are better performing and we do not have to change how we modify them. We also have tossed out the “book” when it comes to how things are done at solar sites. We do not have a south facing centric system, infact we usually have 600w facing south where we have 900w facing east and west. Our batteries are huge 500ah (we calc from 400ah for derating and ensured reserve) Rolls-Surrette locomotive batteries and our whole goal is longer more consistent recharge time vs thebmore common higer current charge for a short time. Our system is off battery usually 2 mins after sunrise starts and doesnt go to battery until just before the sun sets. Actual runtime with 3 ptp links, a single omni AP, sync injectiin by packetflux and sitemon2, c2960s and a isr2951 all at 24v is 3 days (we do not get the sort of heavy overcast days that would kill this setup and we do not get snow buildup due to the combination of steep mount angle and the winds we get). We are usually fully charged by noon as of the current winter trend or before 10am during summer. We can also easily add another set of batteries in parallel to get 800ah (1000ah if you use the manufacturers rating) if we need more run time or are planning to add more hardware. Our heaviest loaded site with 10 radios, Packrtflux sync injection, a c2960s and a isr2951 and with 400ah we have 34hrs of battery run time, all powered by a 30a 24vdc psu (not a solar site but fully dc and except for a mppt charge controller, identical power system). For devices that need 48v (epmp3000), we add a dc to dc boost converter rated large enough to support the current needed load plus room for planned expansion though these can usually be paralleled to provide more avalable current as needed. Our sites have 12v, 24v and 48v loads, we chose 24v as that is the median voltage where most of our loads are. The ciscos are 12v and IP cams (we also have 12v ip cams) and e3k APs are 48v.
We are also toying with adding something like this: ebay ID: 313794988883 to our towers to take advantage of the fact we usually have a 2m/s wind all the time.
My point is, this is very doable once you break from the notion of an inverter must be used and actually looking at real consumption and using that instead of power supply available/max wattage. There are many ways of doing this, Microtik is mostly 12vdc inside though anthing with poe will have a 48v input too.