Why this blog ?

This blog was created to assess the economic benefits of applying green retrofits to your shelter (if you have one) and assess whether it actually makes economic sense at all of having a shelter in the first place (or whether it's cheaper to rent instead). This, as there are often substantial taxes levied on the real estate you own (house, ....) It also looks on whether it is cheaper to own a different kind of shelter (caravan, recreational vehicle, houseboat, ...), and whether it isn't cheaper to simply move to a different climate to be able to slash your heating costs.

Now that the project has progressed, some answers to those questions above have been found:

Owning a shelter or renting ?
A lot depends on whether you all ready have a house (i.e. inherited from your parents, uncle, ...) or whether you'd need to buy/construct a new house. If you have a house, it might be cheaper to keep the existing house, definitely so if you are unable to sell it at the actual value thereof (this will depend on the market value, at that moment).

If you don't have a house, then buying a mobile shelter may be much cheaper if you really want your own place. Often, it will allow you to eliminate real estate taxes you would otherwise be subjected to. If you rather have a regular house, then renting is an option.

Moving to a different country
This seems like an intresting option for many, and it might be, but a lot depends to where you want to move to, and whether it's indeed legal to move to that particular country. First of all, the economics: yes, you would be able to eliminate your heating costs partly or even completely (depending on what country you pick). That said though, the energy costs for heating aren't all that high even in northern countries and you might only be able to save say 500 euro or so. If you also count in the co² offsets, you might be able to save another 500 euro, so say 1000 euro/year in total. You might however end up needing to spend even a lot more on other things (say anti-malaria medicine, ... if you go to countries where malaria is endemic).

Another thing to consider is the legal issues: generally, you are allowed to stay for 1 month or a few months in another country untill you need to leave it. If you have a job by then, you would be able to attain a visa to stay several years or indefinitely. So, this option often won't work for many when picking exotic destinations. However, for some people (like people in the EU), you are able to move from say a northern country in the EU to a southern country thereof (say Italy, Greece, Portugal, ...) without having any legal issues to deal with. You'd also not need to worry about things like malaria, ... and still be able to slash your heating costs by a huge amount. The same goes for people living in large countries like the USA, China, ... By simply moving within the country from the northern part of it to the southern part of it, the same benefits can be attained as for the people in in the EU.

Household budget spreadsheet

The household budget spreadsheet is available here.

The household budget spreadsheet shows the figures for a regular, 25+ year old, family house (4 people) in a central european country. It should be treated as an example, and can be used as a template for others to fill in their own data, and draw their own conclusions thereof (often, things will vary widely depending on the country, and even in a same country, figures can differ a lot depending on the company supplying you.

Clear from the spreadsheet, the fixed fees (subscriptions) are not large at all in comparison to the price per m³ of water, gas, kWh of electricity, ... In countries however where energy, water, ... companies do request high fees, resource conservation via implementing green retrofits in existing houses will never quite take on as the costs of the retrofits are much higher than the economic savings you can actually achieve with them. Even in countries where the fixed fees are not large in comparison to the price per m³ of water, gas, kWh of electricity, ... (as is the case of the family described in the spreadsheet), green retrofits can still cost quite a lot in relation to the expenses you can save with them. In most cases, it will take many years to recover the money spend.

Also, in cases where  the fixed fees (subscriptions) are very large at all in comparison to the price per kWh of electricity, water, ..., going off-grid for power and/or water can be much cheaper than remaining a customer with the power/water company (as you then no longer need to pay the huge subscription costs). It should be noted that whereas you can cancel your subscription , you may obviously still wish to remain physically connected to at least the neighbourhood water/sewerage, ... system (as disconnecting physically would cost money). You would just no longer use it. For power, a complete disconnect could be advisable then though (as that would simplify the system, and protect you from say lightning strikes on the power grid).

Going off-grid for power can be achieved in practice by installing an energy storage system (preferably nickel iron batteries, or alternatively industrial deep cycle batteries; don't use any other types as others typically don't last very long, and are much less ecological). Besides the possible avoidance of fixed fees, the battery pack will allow you to save some money as you can set it to recharge during off-peak hours (this could save you somewhere between 10 and 50 euro). In addition to the energy storage system, you obviously also need a way to recharge your batteries, which can be done by a renewable energy source; for example:
* PV panels (which you might all ready own)
* small-scale wind turbine
* microhydro power plant
* biofuel-powered internal combustion engine with attached alternator or dynamo; note that an internal combustion engine can also be used to heat your water (ie for showering, ...).

It should also be noted that setting-up a truly off-grid system (by combining an energy storage system with a renewable energy plant and also disconnect the connection to the mains electricity grid) won't allow you to supply back any power to the mains electricity grid via net metering. As such, this setup would be less ecologic than a grid-tied system in which you are able to sent back power to the grid. Economically seen though, even by sending back power (and getting paid for this), the solution might still be less financially rewarding than setting up a grid-tied system with net metering. This because, in the event it isn't (say if the power company does not charge hefty fixed fees), you probably wouldn't set up an grid-tied system with net metering anyway as the purchase costs of this equipment would again outweigh the costs of just buying power directly from the energy company.

Going off-grid for water can be achieved by installing a rainwater tank, and having the water from your gutters/rainwater piping connecting to it and (if you want to have it immediately available to your taps, toilet cistern, ...), also add in a pump, and a pressure vessel. The pump can be run from your off-grid energy storage system (if you added that as well).

It should be pointed out however that depending on the country you are in, not only the fixed fees and price per m³ of water, gas, kWh of electricity, ... can differ, but there may also be national programs in place that financially help compensate or even tip over the balance into the right direction. One word of warning though, besides the fact that these may or may not be present, there are often many conditions your equipment needs to adhere to (for example, minimum size of the PV panel array, ...)

Also, the way on how you install and combine the water heating, energy, ... systems in your house can vary greatly.

For example, installing PV panels or solar thermal collectors in a central european country, on a steep roof pointed towards the north will mean the efficiency of the panels will be rather bad in comparison to what they could be when installed correctly (for example, at a flat roof, at the optimal inclination, towards the south).

Also, solar thermal collectors will obviously work much better in hotter countries than in colder countries. Depending on the type of solar thermal collector you own, it may be better to diconnect the power to the pump during winter as it will not improve heating of the boiler during that time (rather it will then cool it).

Another thing to consider is the type of systems you use which also affect performance. Depending on how you use the devices, the type of device may btw also be more or less efficient. For example, you can buy a water heater with a tank or a tankless one, you can have these heated using a fuel/gas or using electricity, if you use one with a tank, you can attach it to a solar thermal collector, ... People that use it every day for showering may be better off with say a version with a tank, and solar thermal collector. Those that don't use it much at all, could prove better off with a tankless one, ... 

Finally, in older houses, older equipment may be present, which still works, but which might not be (well) compatible with "new developments" like net metering, ... For example, in the past (very old houses, say well over 30 years old), single tariff meters were the norm, whereas today, multiple tariff meters are being used. It seems but a trivial thing, but not if you need to buy this yourself (rather than say having it being part of the service ordered and offered by the electrical company). If you need to buy this, you'll find that the purchase cost can be dozens of times the price you might save with the economic gain you can have of say drawing power during off-peak hours (say 100 to 400 euro for the meter installation). It should be noted here however, that most often the meters are rented instead (not bought), so in that case you could just stop paying the rent for that meter and rent another (multiple tariff) one. Off-peak hours are from say 22:00 hr to 07:00 hr. In case you're wondering: no you often can't set your single tariff meter to off-peak hours; it's normally set instead to peak hours.

All in all though, you should generally not see it as an investment that can be recovered, as in many cases, it could just cost you money instead. That said, even if it's economically perhaps not rewarding (again, depends on the country you're in, and what retrofits you actually implement), it does have some other benefits that can't be overlooked; for instance:
* self-sufficiency (you're no longer dependant on any company for your basic necessities like water, power, ...); as a result, power outtages, water cutoffs, ... no longer affects your household
* no risk of  damage or health problems caused by improper management of the companies that otherwise supply you; for example lightning strikes on the power grid can cause many of your appliances to become damaged beyond repair, water contamination of the water grid could cause health problems, ...
* reduction of the amount of carbon offsets you'd need to buy annually to offset your carbon footprint on the planet. Most people aren't offsetting their carbon footprint annually at all; however as natural disasters, caused directly to climate change, claims thousands of lives each year, not doing so actually makes you directly contributable in their passing. It should be noted here that even if you live in a country that has ratified the Kyoto protocol, energy suppliers still only compensate a part of their emissions, as they're allowed to emit a certain amount of carbon dioxide. The easiest way to calculate how much you need to compensate is by just adding up the amount of kWh you spend on heating your house, water, and driving your car (if you have one) and multiplying that by either 0,6 or 1 or 1,5 (0,6 kg in each kWh when using natural gas, see here, 1kg in each kWh when using coal,  and 1,5 when using wood, see here). Nuclear power needs to be multiplied by 0,006, hydroelectric by 0,004, wind power by 0,02, and PV solar panels by (0,10). If you use firewood, but replant it you won't need to calculate that in. The same goes for biofuels (straight vegetable oil, biobutanol, ethanol, ...) coming from crops that are continuously replanted, as well as biogas. Gasoline needs to be multiplied by 2,3 (2,3 kg CO²/liter, see here ) and diesel fuel needs to be multiplied by 2,6. The carbon emissions of the food you consume, the waste you generate, ... isn't added in as these are not really calculatable. The CO² emissions of the house construction itself too isn't added in as we're assuming you are retrofitting and existing house, and the emissions of the construction of that house would have occured a while back, meaning there is no retrievable data on it anymore to calculate the CO² emissions, and/or it may have been done by a previous owner, meaning you're not responsable for it. You can find a list of companies from which you can buy the CO² compensations in the "List of companies supplying VCU's and CER's" post.

If you don't want to spend a lot, and/or have a good financial compensation based on the money put in to the green retrofits, it would help to examine things carefully for your area and only implement those retrofits that offer the greatest savings/cost the least. For example, adding insulation to your roof and plugging holes in your house found with a blowerdoor test could prove quite rewarding/offer the most savings. This is mainly because by far the most energy (2,5 to 3x as much in fact) is lost due to improper heating of the house (see this wikipedia page).Also, again if you offset your annual co² emissions, it too will help the most to reduce the expenses of this.

For newer houses, you'd need to buy new equipment anyhow, and you also don't need to work with the existing infrastructure, meaning that in many cases, the installation can be made simpler/more effective (for example for rainwater harvesting, you could make your house so that you don't need much piping/pumps, ... but instead rely on gravity, ... more). Also, the added cost in relation to the expenses you'd need to do anyhow is comparitively much lower. So with new houses, the economics of implementing green features is often much more positive.

List of green retrofits

The following is a list of green retrofits that can be done in the house, and on your vehicle. This list allows you to quickly compare what green retrofits you are (still) capable of doing, and where the most financial (and/or ecological) benefit can be attained.

1: Install a wood stove with heat exchanger for your central heating system (hot water piping to radiators)
OR install a heat exchanger on your existing stove, fireplace or fireplace insert, and connect it to your central heating system

2: If you use a fuel-oil based burner for your central heating system, swap from using fuel-oil to straight vegetable oil (of which the oil crops are replanted continuously). If you use a a natural gas burner, either change from using natural gas to biogas or to convert your natural gas burner to run on either biobutanol, ethanol or straight vegetable oil as well.

3: If you're using a non-electric water heater (with or without tank), convert the internal heater from using natural gas to run on either biobutanol, ethanol or straight vegetable oil. If you have an electric water heater, keep it as is. You could also attach a solar thermal collector on your water heater regardless on whether you have an electric or non-electric water heater.

4: Add insulation just below the roof of your house. You can also place climbing plants next to your house's walls (making what's called a "green facade") to decrease temperature fluctuations in your house. Another thing you can do to increase the insulative value of your roof is to add an extensive green roof . Adding an extensive green roof is only possible though if you have a roof that is sloped no more than 5%. It increases the lifespan of the waterproof membrane on your roof as well.

5: Install a rainwater tank to water your plants (using 300 or 500liter rainwater tanks/barrels) and/or add a pipe with a tap to your rainwater piping directing water directly to your garden
OR install a large rainwater tank (3000 to 10000 liter) complete with pump, and pressure vessel, and connecting straight to your flush toilets and/or taps in your house.

6: Make a culinary herb patch, vegetable patch, and/or plant some fruit trees in your garden. Also make a pallet compost bin. You can also buy some chickens and/or a goat and keep it in your garden. Alternatively, you can also keep fish if you have a pond.

7: Start using biobutanol or ethanol in your lawnmower (if you have a non-electric lawnmower)

8: Install a battery energy storage system (nickel iron batteries, industrial deep-cycle batteries, ...) and connect it to all your appliances and have the batteries recharged by the mains electricity grid
OR install a battery storage system (nickel iron batteries, industrial deep-cycle batteries, ...) but just connect it to a section of your appliances (ie lighting, ...), and keep the other section of your appliances simply directly connected to the mains electricity grid

9: Install a renewable energy power plant and connect it to your battery energy system and disconnect entirely from the mains electricity grid
OR install a a renewable energy power plant and connect it to your battery energy system while keeping a connection to the mains electricity grid (hence forming a grid-tied system with net metering)

10: Install a biogasifier to generate biogas from the biowaste coming from teh flush toilets

11: Buy some socket outlet boxes (with integrated on/off switch) and connect your appliances to them

12: Convert your diesel car to run on straight vegetable oil
OR Convert your diesel car to run on biodiesel

13: Start using biobutanol or ethanol in your gasoline car

1: You might not always be able to place the wood stove where you'd like (it will depend on where you can attach to the hot piping system). Stoves need oversight/monitoring, so it's best placed somewhere in the living area. The same problem of not always being able to connect to the hot water piping goes for conversions of fireplaces and fireplace inserts. However, fireplaces and fireplace inserts are generally all ready located in the living area, so the oversight problem won't be had here. Don't use it to help heat any water for showering, ... as it only has benefit for heating the hot water of the radiators (in summer, you won't use your radiators/central heating system, but you would still need hot water for showering, hence the reason why that wouldn't work).

2: By changing to straight vegetable oil (ie rapeseed oil, camelina oil, peanut oil, olive oil, ...) as the fuel for your burner, fuel costs could be much lower in comparison to natural gas or fuel-oil. If you change from natural gas to biogas, costs for the fuel would not be lower. However, in both instances, it will allow you to almost completely eliminate the CO² compensation costs you might otherwise do (only those CO² emissions of electricity and perhaps your car's emissions might still need to be bought, but the amount of these emissions is negligable vs your emissions from heating your house). As such, even in the case of swapping to biogas, total costs too could be much less.
In case there is no supplier of biogas in your region, you might be able to convert your natural gas burner to run on straight vegetable oil instead. If that wouldn't work, you could use biobutanol or ethanol, however the fuel costs would then be substantially higher (you would however have lower CO² emissions you'd need to compensate, so that would reduce those costs a bit at least). An alternative solution might be to use straight vegetable oil yet preheat the oil, at least during start-up, as it's the ignition that might prove a problem. (once its operating, no preheating would be needed anymore). Preheating could be done, for example using an electric heater. Keep in mind however that if you use one of these fuels, you'd also need to place a fuel tank, as neither straight vegetable oil, biobutanol or ethanol is being piped to houses in most areas. With biogas, you might not need to install a tank, however, again, it might not always be available in your area.
If you are unable to change the fuel however, you could just sell the entire burner, and buy and install a tankless electric hot water heater instead (so similar as what you might use to heat the water for your taps, shower, ... The hot water heater could then be placed where the burner used to stand, and connect at the same piping of the central heating system. This solution would be much cheaper than using seperate electrical heaters (electric radiators, convectors, ...), and allows you to keep using your hot water radiators. By using an electric hot water heater (for example from power generated from renewable sources, i.e. using a "green power" subscription from a local power company), you'd also be able to reduce the CO² compensation costs you'd otherwise need to do, by a substantial amount. When counting in these CO² emission reductions you would otherwise buy, it would be cheaper than by remaining to use natural gas or fuel-oil (otherwise, when just comparing the costs of the fuels, it would be more expensive; at least when you don't also integrate solar thermal collectors, use off-peak electricity -i.e. using your battery bank you might own-, use the renewable energy power plant(s) you might own, ...). One additional advantage you'll also have when starting to use an electric hot water heater is that you would no longer be dependant on your fuel supplier for heating your house, meaning gas cutoffs during winter will no longer be possible.

3: Only buy and attach a solar thermal collector if you have a flat roof, or if you have a steep roof, but when your house's roof is optimally oriented (towards the south) and can be optimally tilted using a custom mounting frame.

4: Whereas adding insulation below the roof of your house is a popular solution, and very effective to reduce heating costs, and reduce the CO² compensations you might buy, it is only practical if you haven't all ready added sufficient insulation below your roof (which might or might not be the case). Also, even if you don't yet have sufficient insulation, it might still be difficult to achieve, especially if you have a dropped ceiling. Note that besides insulating the roof, you can't really insulate any other sides of the house (walls, ...), at least not easily, so just focus on the roof or skip it entirely if the roof can't be insulated easily.

5: The first solution is by far the cheapest solution, and also the easiest one to accomplish in practice. You just need to dig in the rainwater barrel or tank into the ground (below frost line) and connect it to the rainwater piping which are hooked up to the gutters. You'll also need to have a pipe sticking out of the ground in which you can insert your manual pump's inlet pipe. Old manual waterpumps may still be obtainable in your area, or you can buy the KickStart Hip Pump, or make your own PVC pump. In countries where it doesn't freeze at all, you won't even need to dig in the tank completely, and instead, you could just use a bucket to collect water from it -ie via a built-in tap on the tank at the bottom, or an open top-. The overflow can connect to the sewerage (in case that was all ready the case before you converted it) or you can have it run to the garden.
A variant to this is to not use any tank at all, but just connect a pipe with a valve straight on your rainwater pipe, directing water directly to the garden. It isn't even necessary to have the pipe run to near where your plants are; rather, their roots will be able to find the water anyway. A tap is best added so you can easily close off this added pipe and redirect the water again to the initial pipe (which for example connected to the sewerage). This tap is useful if you find that the earth has been saturated enough for the time being. Also, you can also use a combination of both these solutions (directing water straight to the garden from your rainwater pipe, and using a water tank, and overflow to the garden or to the sewerage). Using a combination may be more practical/efficient in instances where you have several roof parts collecting rainwater and thus several rainwater pipes as well.
If you don't know where the rain pipes are in the ground, refer to your building plans (which should have been supplied to you by your architect).
The second solution (installing a large rainwater tank complete with pump, and pressure vessel, and connecting straight to your flush toilets and/or taps in your house) will allow you to use your water much more effectively/use more of it. However, it's also much harder to do in practice, and costs a lot more. On the long run however, it may be even much more economical though.

6: Making a culinary herb patch will probably allow you to save most money at least considering the little effort that you need to put in. A vegetable patch too allows you to save quite a bit of money as vegetables too are rather expensive nowadays. Wooden boxes with a glass plate on it ("cold frames") can allow you to extend your growing/harvest season for herbs and cost little. Fruit trees finally also save you money, but as often, more fruit is produced in the harvest season than what you can actually consume in that period, you'd need to also combine it with preservation methods (ie making jam of it, drying -ie using a home made solar dehydrator-, ...)
Chickens are small enough to keep in your garden and also require few maintenance and housing costs. The same goes for a goat, all though you would need a somewhat larger garden for that. You would also need to set up fencing for the chickens (or use a chicken tractor), with a goat you can have it fastened with a long rope to a post. With both, you might feed it (to some degree) with leftover kitchen scraps and/or garden waste (leaves, worms, ...). Any leftover kitchen scraps or garden waste that the animals don't eat can be put on the compost bin (or immediately dug into the soil, which is also called "trench composting"). Don't try to hold anything larger than a goat though (no cows, ...) as these require far too much space for most, are less hygienic to keep, and produce too much dairy for most families anyway. Fish can also be kept, for example if you have a (freshwater) pond. Do make sure however your pond is then balanced out enough (oxygen plants, submerged plants, filtering medium (lava stone, ...), filtering plants rooting in lava stone, pump, ...), that your pond is deep/large enough to cope with temperature changes, and that you're not keeping too much fish neither. Else, you might end up with having algae and dead fish (due to too little oxygen being in it).

7: If you have a non-electric (4-stroke, gasoline) lawnmower, you can only use biobutanol or ethanol. Biobutanol would work immediately, with ethanol, the carburettor's settings may need to be changed, you could ask to have this done in a local garage if you don't know how to do this.
Regardless of whether you'd switch to biobutanol or ethanol, you'll be able to reduce the CO² compensations you'd otherwise need to buy considerably.

8: the first solution is obviously the cheapest one, as you don't need as much battery capacity as with the second solution. Depending on what appliances you select it may also allow you to save on parts you might otherwise need. For example, some appliances may be able to run directly on DC power too (i.e. LED lighting, ...), meaning you don't need an inverter to transform the DC power from the battery to AC power for those appliances. Also, you might be able to avoid needing additional transformers, ... As such, it may be useful to examine your current electrical system first, and perhaps do some changes here and there (for example, changing some or all of your incandescent or halogen lamps to LED lightbulbs, LED or LEC strips). This would reduce your energy consumption a bit, and hence also reduce the battery capacity you need.
The second solution is more expensive, but does allow full independence from the grid for a limited duration (ie as in the case of a temporary power outtage); the first solution only allows partial independance (ie during power outtages, your lights, ... can be made to still work, but you'll lose the ability to use other appliances). Both solutions will allow you to save some additional money (10 to 50 euro) as you'll also have the ability to recharge your battery to power some or all of your appliances during off-peak hours (off-peak hours are generally from 22:00hr to 07:00hr). You would be able to set it during that period to recharge by using a time switch.

9: as discussed in the "Household budget spreadsheet" post, what system ends up being the most economical depends on how your energy company charges you for the power you consume. As too mentioned in that post, renewable power plants you could use include:
* PV panels (which you might all ready own)
* small-scale wind turbine
* microhydro power plant
* biofuel-powered internal combustion engine with attached alternator or dynamo; note that an internal combustion engine can also be used to heat your water (ie for showering, ...).
If you all ready have PV panels installed on your roof, you may want to make sure the tilting has been done correctly, and if it isn't, calculate out the the optimal inclination, and adjust the mount frame accordingly, or have this done by a professional. Also, if besides the inclination, the direction -i.e. towards the south in countries in the northern hemisphere- is also incorrect, you may want to see whether there isn't another location where you can place the PV panels instead.
A list of other suitable small-scale power plants can be found here.

10: I mentioned this for reference sake; all though this might seem a good idea at first, the biogas that can be created (even by a family of 4) is nowhere near sufficient to run say your internal combustion engine on it (assuming you have one, ie to recharge your battery energy storage system). It's only useful for say cooking and lighting purposes, by using direct incineration of it (for this reason it's being used a lot in certain developing countries).

11: It may not seem like much, but inserting all the power plugs of your appliances to a socket outlet box with integrated on/off switch allows you to switch off many devices at once, which is still practical to do in real life, and allows you to make sure those appliances no longer draw any "standby" power. Socket outlet boxes don't cost a lot, and will allow you to save quite a bit of money as some appliances (TV's, ...) may still draw say 50% of their power even when not operating.

12: Converting your diesel car to be able to run on straight vegetable oil can be done by bying a conversion kit (which contain electric preheaters for the oil, an oil filter and an extra pump to increase pump pressure). These kits are available by many manufacturers, see here. You can do the conversion yourself, or just have a local garage/mechanic do it.
If you are unable to do it yourself, or find a local garage/mechanic to do it for you, you can also just buy biodiesel, which is straight vegetable oil that is chemically treated so that it will run in any diesel engine. Regardless of what method used, you'll be able to reduce the CO² compensations you'd otherwise need to buy considerably.

13: If you have a gasoline car, you can only use biobutanol or ethanol. Biobutanol would work immediately, with ethanol, it would work only if you have a car with a carburettor (with direct injection, it can work too, but it's much more complicated as you'll need to modify the engine control unit). The carburettor would need to have its settings changed, you could ask to have this done in a local garage if you don't know how to do this.
Regardless of whether you'd switch to biobutanol or ethanol, you'll be able to reduce the CO² compensations you'd otherwise need to buy considerably.
Note that some other options for gasoline cars exist, such as converting to electric (by swapping the engine with an electric engine and adding batteries), or swapping the gasoline engine with a diesel engine (see above). Both these methods however tend to be very expensive options, and technically tricky. Best not to do this as such, unless you have a great amount of technical know-how.

List of companies supplying VCU's and CER's

Below, you will find links to articles with lists of companies that supply VCU's (verified carbon units) or CER's (certified emission reductions). Both types are basically the same (CO² emission reductions from either planting trees, or other projects in which the emission of carbon dioxide has been avoided). VCU's and CER's differ only in that the organisation that performs the control is different, and the first tends to focus on regular consumers (private people) whereas the latter focuses mainly on companies that actually need to offset a part of their emissions, as required by law.

The best off-sets you can buy are those of REDD projects (see here), mainly as in these projects, existing forests are left standing, meaning the local fauna/flora in them are kept intact -by comparison, regular tree planting projects may involve just making new forests on cleared land, using non-native tree species-.

Other projects still are projects in which emissions have just been avoided using other means (for example by making existing power plants made less polluting, ...)

Regardless however of which project you prefer to buy the credits from (often, you can select this yourself !), the most important is that you indeed offset all your emissions you generated anually (rather than not doing it at all).

Links to articles with carbon offset provider lists:
* Endscarbonoffsets
* UNFCCC's CDM site
* CORE: offset providers

PS: the family featured in the spreadsheet used companies as Trees for all , CoolEarth, World Land Trust, ...