Net Metering v Net Billing

[Anarita John]

In the UK we have Net Billing, similar to the system EAC have introduced. However, with a wide range of suppliers and smart meters being readily available,we can choose time based tariffs whch give us a good return for our surplus energy. We currently get £0.31 per Kwh for export between 4pm and 7pm and our battery ensures we export at least 12Kwh at this rate.

The question a lot of people are asking, is it now worth getting solar panels now that EAC have done away with Net Metering. I've done some very crude working out from my figures for 2022/2023. I'm not a Mathematician (CSE Grade2) so they may be completely wrong.

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Months shown are when I receive my bill from EAC, so May is for March and April. Difference between produced and total used is self explanatory,total used being the electric I used through the meter and electric I used from solar panels. Export value of difference is the amount I would have been paid for surlus energy, or, in the case of a negative return as in January, how much I would have paid to EAC.

The reason January is so high is because we heated our pool during November and December, and again in March and April. We alsouse our aircon freely for cooling during the summer.

Surplus energy, Export Value worked out at €0.11 per Kwh. Cost,Non solar is what our EAC bill would have been without PV panels, worked out at €0.29 per Kwh. Also, the negative difference in January was worked out at €0.29 per Kwh.

My conclusion is under the new system,PV panels plus a battery are worth it. If, after 15 years,we have to go onto the new Net Billing system,the first thing I would do is buy a battery. Also, think of other ways of heating our house. At present we use air con for heat in winter, set at 22c in living areas and 18c in bedrooms. Maybe slimline storage heaters which could use surplus energy during the day in the main living areas.

Also, choose your installer carefully. Make sure that you are going to be using all of your solar energy for home and battery topup and not exporting to the grid, whilst you are producing energy sufficient for your home use. (the ev home charger Greenair have installed for us takes electric from all 3 phases, most only from 1 phase so you end up drawing from the grid)

[mark4007]

Hi
Useful exercise but I am not convinced by the methodology you have used.

I cant find anything on the EAC that shows how this will work going forward. However my understanding is that the current system for net billing is as follows

Credit for export to go against the bill

Any excess credit to get carried forward against future billing period

So in your model I think you need to look at gross exports (rather than, as you have used, the net difference between produced and total used)

If the export value of the difference is negative this is irrelevant as you only get credits for exported units there is no claw back for deficits in a period

The comparison is between what the bills will be under net metering and “non-solar”

I have done a similar exercise to you (but alas cant figure how to get a table showing figures into this discussion)

My figures suggest a saving in 2023 for me of 1,678 (diffence between net billing cost for year and a system that has no PV)

so not a million miles from your calculated saving.

But..

Should someone enter into a new net billing scheme?

I am not convinced – the saving above says yes but its ignoring two crucial issues the battery and curtailments.

The battery cost will be high (probably more than the cost of the PV install) and have limited benefit. (If no grant I estimate the payback for the battery on its own will be something like 20 years ...)

More importantly curtailments are and will continue to be a real issue for those unfortunate enough to have the ripple cut off switch imposed. There are no signs that this will get better for consumers. In fact I expect them to get worse for the next few years irrespective of whether or not anyone actually signs up for the new net billing scheme.

If the EAC continues to turn off household PV production then this will have a significant impact on whether or not a net billing scheme is worthwhile.

Even if new installations are only restricted to being prevented from exporting then this will still push back payback periods and the uncertainty may put off households from making an investment.

[Anarita John]

As I said, I am not a mathematician or statistician and my figures are probably very crude. We still have 9 years to go on our Net Metering contract and as long as EAC honour it, we would not need a battery. However, when the time comes, and we go onto Net Billing, a battery seems to be the way forward. Hopefully there will be grants available. 20Kwh of battery storage would be sufficient to heat our house and fuel our appliances, plus heat our pool when the weather is not too cold, eg Nov, March, April.

Again, I am no expert, but what needs to be addressed is making sure all the electric you produce is used by the home(or top up the battery) and you are not importing from the grid when you are producing enough electric from solar to fuel those appliances.

[mark4007]

Hi

Sorry, I thought what you were trying to model was whether people without PV should enter into the new net billing contact. You indicated they would certainly be better off by doing so. my analysis is that it depends on:

1) whether it is compulory to buy a battery and how much the grant is for the battery and
2) whether the EAC will install a ripple cut off switch.

As for what decision needs to take place in 9 years time, then what is certain is that the decision factors there are now will have completly changed by then.

My belief is that the australian experiment with V2G will mean that in 9 years time we will not need a big battery in the house... instead we will need a bidirectional charger and an electric car...

in addition i think you are looking at this in the wrong way.. the economics of solar power are such that it is better to have an oversized PV array and "waste" electric generation in the summer if that leads to a reduction in the battery size you need in the winter..

[jeba]

What will EAC pay per kWh exported to the grid under the net-billing scheme? For how long will the price be guaranteed?

[mark4007]

The EAC will not pay anything for the exported units - instead you get a credit against your next EAC bill and its not clear as to how much the credit will be (€0.08-0.10/kWh?)

There is a real issue here - there are many businesses which provide solar power installations to domestic premises - how many of these will have to cut back on staff etc in the very near future as no one will be wanting to install PV under the new net billing arrangements (unless they ditch the battery requirement (as they did before PV for all was introduced)