Hybrid Solar Systems Part 3: Costs and Payback

What’s the payback?

Note: This post was written in 2012 and is way out of date. For the latest payback figures  please read this page which is kept up to date >>> Are Solar Batteries Worth It

In my previous 2 posts I looked at the concept and design of Hybrid Solar systems.

The main conclusion of those 2 articles was that

a) Hybrid solar rocks!

b) But you gotta pay for it!

So the question this post will try to answer is:

How Much Extra Does Hybrid Solar Cost?

and bearing in mind the extra costs:

What is the payback of Hybrid Solar Compared To Regular Grid Connect Solar?

So let’s look at the cost of a quality 5kW system and then see what it costs to upgrade it to “Hybrid”.

Cost of a 5kW grid connect system (April 2011 pricing) :

5kW of good quality panels: $8,000

5kW inverter: $3,000

Racking and cabling: $1,000

Install: $2,000

Less Solar Credits (approx 165 STCs @ $25):  -$4,000

Total cost: $11,000

Cost of a 5kW Hybrid solar system:

5kW of good quality panels: $8,000

5kW inverter: $3,000

Power management unit: $3,000

Batteries (to store 10kWh):  $3,000

Racking and cabling: $2,000

Install: $3,000

Less Solar Credits (approx 165 STCs @ $25):  -$4,000

Total cost: $18,000

So, for  a 5kW system – expect to pay at least $7k more for the hybrid option.

So the question is – if you are going hybrid to avoid a miserable Feed In Tariff, like NSW’s 7c per kWh – then what is the payback on the extra expense?

Let’s crunch the numbers using my solar payback calculator:

Scenario 1 – Grid Connect System:

Key assumptions are : we export 50% of our solar power @ 7c per kWh, and we offset our electricity bill @ 26c per kWh with the other 50%.

(Read this article If you are confused about importing and exporting solar electricity)

The calculator looks at the cash-flow of this solar system for 20 years. It takes into account:

• electricity price inflation
• the “opportunity cost” of not having the cash you paid for the solar system in the bank earning interest instead
• power degradation over time as the panels age

For a system cost of $11,000 here are the results:

The payback calculations for a 5kW Grid Connect Solar System : 12 years

The payback of the 5kW grid connect system is 12 years when exporting half your power for a pitful 7c per kWh.

Scenario 2: 5kW Hybrid System.

The 5kW hybrid system comes with about 10kWh of battery storage. A 5kW system produces about 20kWh per day. So it should be capable of storing and shifting the 50% of the solar power that was previously being exported. We can use that power to offset our 26c per kWh bill instead. If this was to happen what would the payback be on the hybrid system?

To find out, I simply changed the price of the system to $18,000, and changed the % of electricity being exported from 50% to 0%. Here are the results (with the changes to the calculator inputs highlighted):

5kW Hybrid Solar System pays back in 11 Years

With those (very big) assumptions, the payback comes out at 11 years! Hybrid solar appears to be a better investment…woo hoo!

But.. it isn’t that simple I’m afraid…my experience is that the batteries in such a system will need replacing after about 10 years.

Luckily our calculator can handle that. I originally programmed it to include the option of replacing the inverter after a number of years. If we use this option to show us the effect of replacing $3,000 of batteries after 10 years, then the payback comes out at 13 years. One year longer than the non-hybrid system:

New batteries after 10 years add 2 years to the payback

So in this example – assuming the batteries last 10 years, and cost you $3,00 to replace (many people would argue that batteries will reduce in price drastically in 10 years), your hybrid system is a slightly worse investment that non-hybrid.

But I’ve made a hell of a lot of assumptions:

• about how much electricity is exported
• what the feed in tarrif will be 10 years in the future
• how much electricity prices will rise
• etc, etc.

The long and short of it is that – the extra cash you spend on a hybrid system should pay for itself over about 10 years if the feed in tariff in your state is (and stays) very low. Combine that with the advantages of blackout protection, and the satisfaction of not giving almost-free electricity to the retailers and hybrid solar starts to look tempting. And as battery costs and the cost of the power management units come down, it is only going to become more viable.