Whilst the savings for every user is different, on average our users are saving more than $100/year (AUD).
We’ve been tracking charging stats for our users since September 2022 which provide some reliable guidance on how much charging from solar you can achieve.
The following graphs are based on data from a cohort of users across Australia. There’s a concentration on capital cities and there’s a big variation on how much sun different users get from north to south of the country.
In the summer months, we see averages exceeding 70% and dropping below 60% in October.
Drilling down to the individual user level across the same period of time you can see a significant spread. More than half the users source over 70% of their EV charging from solar.
Lastly, we’ve graphed estimated annual savings for this user cohort by extrapolating the data we have (only the sunnier half of the year) to a full year and assuming a price difference between grid-supplied energy and the feed-in tariff of $0.10.
The current data set suggests average savings of around $140/year and median of around $125/year with an adjustment for the winter months.
Your individual savings are determined by a combination of:
Let’s work through each one.
Without solar charging, most EV owners charge their cars overnight from the grid, so the cost of charging is the rate that you buy power at overnight.
For some users, power is the same price all day but for others, power is cheaper overnight.
Every kWh of charging that comes from your solar is a kWh you don’t have to buy from the grid, but it’s also a kWh you don’t get paid for exporting to the grid.
The saving for each kWh = grid price minus the export payment price (or feed-in tariff).
So, if you’re buying power at $0.25/kWh and get a feed-in tariff of $0.05/kWh, charging from solar saves you $0.20 for each kWh.
If your solar system is making a lot more power than your home is using you’ll have plenty to use for EV charging. If you have a small solar system and aren’t exporting a lot you might not have enough to meet your EV charging needs and some of your charging will still come from the grid.
How much solar you can make use of for EV charging also depends on how much of the time your EV is home when the sun is out. If you’re regularly at home during the day you’ll be able to capture a lot more solar energy than if you drive your EV to work each day.
You can only use your solar to fill up your EV battery, once it’s full you can’t use any more. If you do a lot of driving, your battery will have space to absorb excess solar more of the time. If you only do a small amount of driving you might find you quickly recharge your battery without using much of your solar energy.
To estimate your individual savings, multiply:
kWh of EV charging per year * percentage charging from solar * solar price delta
For example, if you’re an average driver doing 15,000 kms per year, in say a Tesla Model 3 using say 180 Wh/km, and you can get 60% of your charging from solar with a price delta of say $0.10, you’ll save: 15,000 * 0.18 * 0.6 * $0.10 = $162/year.
If you’re an existing Charge HQ user you can calculate your savings using the stats provided. From the stats tab, use the year view and read the “From Solar” kWh value, then multiply this by the difference in your feed in tariff and your overnight or off-peak grid supply price. If you don’t have a full year of data you can extrapolate from the period you do have - noting that winter will generally see less solar charging than summer periods.
For example:
